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BDS 1 > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

What is a cell?

A

Basic structural, functional and biological unit of all living organisms
Smallest unit of life replicate indecently
Require nutrients and produce waste

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2
Q

Describe the cell membrane

A

Selectively permeable biological membrane separating interior and exterior of cell and protecting from surroundings
Involved in cell adhesion, ion conductivity, cell signalling, attachment surface for cell wall, glycocalyx (glycoprotein-polysaccharide surrounding CM of some bacteria and epithelial) and intracellular cytoskeleton

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3
Q

Describe the phospholipid bilayer

A

Made of hydrophilic heads and hydrophobic tails
Phospholipids spontaneously form self-sealing bilayers
Due to hydrophobic interior charged ions cannot diffuse
Fluid - components move around easily
Mosaic - variety of lipids and proteins

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4
Q

Describe centrosomes

A 
Associated with nuclear membrane in prophase
In mitosis, NM breaks down and centrosome nucleated microtubules (cytoskeleton) interact with chromosomes to build mitotic spindle
Mother centrosome (oldest) role in making cilia and flagella
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5
Q

Describe lysosomes

A

Membrane bound organelle that functions as recycling centre by digesting unwanted material in cytoplasm from extracellular and obsolete intracellular components
Contains hydrolytic enzymes capable of digesting almost all biomolecules: proteins, nucleic acids, carbs, lipids, debris
50+ enzymes all active at about pH 5

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6
Q

Describe the cytosol/ICF

A

Liquid found inside cells separated into compartments by membranes i.e. mitochondrial matrix separates cells into compartments
Eukaryotes - ICF in CM and part of cytoplasm (mitochondria, plastids, organelles minus internal fluids and nucleus

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7
Q

Describe the vacuole

A

Membrane bound organelle filled with water containing in/organic molecules (enzymes in solution), sometimes engulfed solids
Formed by fusion of multiple vesicles
Shape and function varies depending on needs and type of cell
Role in autophagy, balance between biogenesis and degradation, lysis and recycling of mis-folded proteins

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8
Q

Describe mitochondria

A

Membrane bound organelles
Main functions are to produce ATP in TCA (respiration) and regulate metabolism
Role in - signalling through mitochondrial reactive O2 specifies
Regulate - MP, apoptosis, Ca signalling (including Ca-apoptosis), cellular metabolism, heme and steroid synthesis
Have oestrogen receptors (mtERs) thus sensitive to hormones
In liver cells, have enzymes that detoxify ammonia (waste product of protein metabolism)

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9
Q

Describe the smooth ER

A

Site of lipid, phospholipid and steroid synthesis connected to nuclear envelope
Abundant in cells (ovaries, testes, skin oil glands) that secrete these products
Metabolism of carbs and steroids, drug detoxification, attachments of receptors on CMPs
Muscle cell - regulates Ca ion conc.

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10
Q

Describe the cytoskeleton

A

Dynamic structure made of microfilaments (actin), microtubules (tubulin) and intermediate filaments (only found in animal cells) forming framework for movement of organelles and cell shape

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11
Q

Describe the Golgi body

A

Modifies, sorts and packages macromolecules for exocytosis or use with in cell primarily those delivered by RER
Transports lipids and involved in creation of lysosomes
N/O-linked goycosylation

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12
Q

Describe the rough ER

A

Complex responsible for manufacture of lysosomal enzymes (mannose-6-phosphate marker added in cis-Golgi network)
Manufacture of secreted proteins secreted either constitutively (no tag) or regulatory (clathrin and basic AA in signal peptide)
Initial stage of N-linked glycosylation

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13
Q

Describe a vesicle

A

Variety of functions
Internal environment different from cytosolic as is separate from cytosol thus used for organising cellular substances
Involved in metabolism, transport, buoyancy control, enzyme storage (ready for immediate release), chemical reaction chambers

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14
Q

Describe ribosomes

A

Site of gene translation
Attaches to mRNA, reads codon. tRNA with complementary anti-codon recruited bringing specific AA building protein.
Continues until reaches stop codon, if none will remain attached forming complex

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15
Q

Describe the nucleus

A

Cell control centre: maintains integrity of genes and regulates gene expression
Contains DNA and histone proteins to form chromosomes
Has double membrane enclosing entire organelle isolating from cytoplasm, nuclear envelopes and nucleoskeleton (like cytoskeleton)

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16
Q

Describe nucleolus

A

Organelle found in nucleus that forms around specific chromosomal a previous in nucleus
Made of proteins and RNA
Transcribe and modify rRNA and integrate ribosomal proteins into immature ribosomes
Stress sensor and able to regulate rRNA synthesis based on cell environment

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17
Q

Describe the differences between prokaryotes and eukaryotes

A

Lack membrane bound nucleus (have nucleoid) and complex organelles
Ribosomal binding site in mRNA is the Shine Delgarno sequence: 8 bases up from AUG
Have mesosomes - folds inwards in PM that increase SA, can be artefact (damage to PM during chemical fixation)
Have cell wall, capsules and flagella (chemotaxis - movement of organism in response to chemical stimuli

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18
Q

Describe gram +ve bacteria (purple)

A

Thick cell wall of peptidoglycan which is mesh that gives strength
Cell would be spherical and v sensitive to osmotic changes without

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19
Q

Describe gram -ve bacteria (red)

A

Complex cell wall external to PM with thin peptidoglycan layer
Have outer membrane with lipopolysaccharides conferring
Structural integrity, resistance to chem. attack, toxicity (septic shock, death)

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20
Q

How do many antibiotics work?

A

Act by inhibiting cell wall synthesis

B-lactam antibiotics (Penicillins) interfere with peptidoglycan synthesis causing cell lysis

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21
Q

What is pH?

A

Logarithmic measure of conc. of H+ ions (protons) in solution
pH = -log[H+]

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22
Q

What is the physiological pH of the body and why is this important?

A

pH 7.4
pH affects solubility of substances and the activity of biological systems thus keeping pH constant is important for body
Blood pH<7.3 acidosis
Blood pH>7.5 alkalosis

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23
Q

Define acid, base, conjugated acid and conjugated base

A

Acid - proton donator, gains -ve charge
Base - proton acceptor, gains +ve charge
Conjugated acid - species formed from addition of H+
Conjugated base - what is left after acid donates proton

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24
Q

What is the major respiratory acid in the body and how is it formed?

A

CO2
Dissolved in water forming carbonic acid which dissociates releasing H+
CO2 + H2O H2CO3 H+ + HCO3-

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25
Q

Name some metabolic acids and how they produced

A

Organic (lactic, uric) and inorganic (sulphuric) produced by metabolism of AAs containing phosphorus and sulphur
Lactic - product of anaerobic glycolysis
Keto acids - ketoacidosis, lack of insulin
Drugs - aspirin

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26
Q

Define buffer

A

Solution that resists changes in pH when acid/alkali is added to it
Usually a solution of weak acid and its conjugate base
Biological fluids have ENDOGENOUS buffers

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27
Q

How do buffers work?

A

Weak acid will partially dissociate and salt will fully dissociate allowing H+/OH- ions to be added and equilibrium will shift to replace the lost molecules
As one fully dissociates more ions will be produced and not removed

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28
Q

What are the main buffers in the body and where are they found?

A

Haemoglobin (HHb) found in red blood cells
Proteins (HProt) in intracellular fluid
Phosphate (H2PO4-) in intracellular fluid
BICARBONATE (CO2->H2CO3) - blood plasma, interstitial fluid

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29
Q

Define buffer capacity

A

Extent of resistance to pH change i.e. how much acid/base added before pH changes dramatically

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30
Q

What is the dissociation constant?

A

Kd - Type of equilibrium constant that measures the dissociation of larger compound to split reversible to smaller components

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31
Q

What is pK(a)?

A

The pH at which 50% of the HA (acid) has ionised

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32
Q

What is the Henderson-Hasselbalch equation?

A

pH = pK + log[A-]/[HA]

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33
Q

What is the relationship between pH, pKa and ionisation?

A

If the pKa is higher than pH, acid is less likely to be ionised

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34
Q

What is critical pH?

A

pH at which tooth becomes unsaturated with respect to Ca and PO43- allowing hydroxyapatite in enamel to dissolve
Region of pH 5.2-5.5

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35
Q

How does saliva protect teeth from decay?

A

Produces many buffers (principally bicarbonate) which prevent resting pH falling much lower than pH 6.3

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36
Q

What are the main buffers in saliva and how effective are they?

A

Proteins - not effective as nearly all charged groups from peptide bonds
Phosphate - good but not in high enough conc. to be effective
Bicarbonate - good

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37
Q

What is the role of bicarbonate in plaque?

A

Acts to neutralise acid rather than buffer acid

Produces H+ pushing reaction to right producing CO2 and H2O - CO2 released as mouth open system

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38
Q

What conc. does carbonic acid stay at in the mouth and what changes?

A

About 1.3mMol/L

pH and [HCO3-] change, bicarbonate varies with flow rate

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39
Q

What must all AAs have?

A

Amino (NH2), carboxyl (COOH), H and R group

a-carbon is C atom amino and carboxyl groups are attached

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40
Q

What is the role of side chains?

A

Are the functional groups
Determine structure, function and charge of AAs
Charged, polar or hydrophilic R groups exposed on surface
Non-polar, hydrophobic R groups buried in interior

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41
Q

What confers an AAs’ optical activity?

A

An asymmetric C atom - C attached to 4 different groups

All AAs except GLYCINE (R group = H) are asymmetric

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42
Q

What does being asymmetric mean?

A

Means compound has spatially distinct but chemically identical isomers that are mirror images of each other (enamtiomers)
Both are optically active (rotate plane polarised light) to right (Dextro) or to left (Levo - majority of AAs)

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43
Q

What is a zwitterion?

A

A molecule that bears groups of opposite polarity

As amino and carboxylic acid groups readily ionise AAs are dipolar/zwitterions

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44
Q

How does the charge of AAs change with increasing pH?

A

Low pH - amino protonated, carboxyl normal
pH 7 - amino protonated, carboxyl ionised
High pH - amino normal, carboxyl ionised

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45
Q

Define AMPHOTERIC

A

Molecules that have both acidic and basic groups

AAs are amphoteric

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46
Q

Define anion

A

A negative ions from gain of e-

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47
Q

Define cations

A

+ve charged molecule

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48
Q

Name the aliphatic AAs? (Hydrophobic/non-polar)

VIGAL

A 
V - valine
I - isoleucine
G - glycine
A - alanine
L - leucine
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49
Q

Name the aromatic AAs

Y+T

A

Phenylalanine (phenol - aromatic)
Tryptophan (Y + T = aromatic)
Both non-polar
Tyrosine (Y + T)

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50
Q

Name the sulphur containing AAs

MC Sulphur

A

M - methionine
C - cysteine (can from S-S, stabilise proteins)
MC Sulphure

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51
Q

Name the neutral polar AAs

A

Hydroxy-Soft Towel
Serine
Threonine

Amide derivates of Acids
Asparagine
Glutamine

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52
Q

What is the ImIno acid?

A

Proline - causes bends in polypeptides

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53
Q

Name acidic AAs

A

Aspartic acid
Glutamic acid

COOH R group - ionised at pH 7

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54
Q

Name the basic AAs

Larry is basic

A

L - lysine
Ar - arginine
His - histidine
LArHis - extra +ve charge

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55
Q

What formula is used to calculate the isoelectric point? How is this calculated for amino acids with 2 carboxyl/amino groups?

A

pI = (pKa + pKb)/2
a (acidic) = COOH b (basic) = NH2
For 2 carboxyl groups the (pKa1 + pKa2)/2 is used

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56
Q

What is a dalton?

A

Da is a unit of molecular weight equivalent to 1 H atom

Compares how heavy something is to H

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57
Q

Describe the primary structure of a protein

A

Unique sequence of AAs held by peptide bonds

Compare structure to find common sequences suggesting members of a multigene family

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58
Q

Describe the secondary structure of proteins

A

H bonding determines secondary structure either a-helix or B-pleated sheet

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59
Q

Describe boding in and structure of an a-helix

A

N atom in peptide bond shares H atom with CO group 4 residues upstream
Polypeptide twists around in a spiral, each turn takes 3.6 AAs residues

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60
Q

Describe B-pleated sheets

A

B strands laterally connected by 2/3 H bonds

Typically 3-10 AAs long

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61
Q

Describe the tertiary structure of AAs

A

Folding of secondary requiring series of non-covalent interactions
Held by electrostatic, VDWs, disulphide, hydrophobic interactions

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62
Q

What are electrostatic bonds?

A

Strong interactions between ions/charged groups of opposite charge
In protein called a salt bridge

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63
Q

What are Van der Waals forces?

A

Weak, close range temporary dipole-dipole interactions

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64
Q

What are disulphide bonds?

A

Strong covalent S-S bonds between specific cysteine residues
Tend to lock molecule into configuration allowing it to withstand v high temperatures

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65
Q

What are hydrophobic interactions?

A

Interactions between polar and non-polar molecules causing the spontaneous folding of hydrophobic residues away from water

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66
Q

Describe the quaternary structure of proteins

A

Association of multiple tertiary polypeptides

Haemoglobin is association of 4 globin groups and 4 heme groups

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67
Q

What is a protein domain?

A

Part of a polypeptide that can fold independently of polypeptide into compact, stable tertiary structure
Usually identified by presence of prolIne
Can be cut, isolated and studied separately from main chain

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68
Q

What is protein folding?

A

Process by which higher structures are formed from primary (AA) sequence

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69
Q

What are transitions in shape of tertiary or quaternary structures called?

A

Conformational changes - proteins may shift between several similar structures in performing their function
(Tertiary and quaternary structures referred to as conformations)

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70
Q

What is the reversible nature of protein folding dependent on?

A

Primary structure being maintained

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71
Q

What are the three classes of proteins?

A

Fibrous
Globular
Membrane-associated

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72
Q

Describe globular proteins

A

Are soluble, nearly all enzymes are globular

Carbonic anhydrase and haemoglobin are examples

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73
Q

Describe carbonic anhydrase

A

Catalyses interconversion of CO2 + H2O to carbonic acid
Different classes have little sequential or structural similarities but share identical AS thus all perform same function and require a Zn atom
Contains large B sheet in centre

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74
Q

Describe haemoglobin

A

Assembly of 4 globular protein subunits each composed of protein chain (2 a chains, 2 B chains) tightly associated with prosthetic heme group

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75
Q

What is a prosthetic group?

A

Non-protein group tightly bound to protein that confers function
Heme has an Fe atom held in heterocyclic ring equally to all 4 N atoms
Fe is site of O2 binding

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76
Q

Describe fibrous proteins

A

Form rod/wire like shapes, usually structural or storage proteins
AA sequence often lacks repeating units
From unusual 2ndary structures (collagen triple helix) due to cross-links between chains e.g. S-S bonds between keratin
Usually used to construct CT, tendons, bone matrix, muscle fibre

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77
Q

What are keratins and what do they form?

A

Family of fibrous structural proteins, they are tough and insoluble
Form non-mineralised structures found in reptiles, birds, amphibians, mammals (hair)

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78
Q

Describe the structure of keratin

A

High proportion of glycine (smallest) and alanine (2nd smallest) AAs
High amounts of cysteine (sulphur containing) required for S-S bridges confer strength, rigidity by permanent, thermally stable cross-links

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79
Q

Describe the structure of keratin monomer and the assembly into intermediate filaments

A

3 domains: head, rod, tail

Monomers associate to dimers, associate to tetramers, finally to intermediate filaments forming part of cytoskeleton

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80
Q

What is collagen?

A

Family of fibrous proteins secreted by CTs with triple helix AA structure
28 different types
Unique sequence of glycine-proline/hydroxyproline-alternative AA

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81
Q

What are the 3 type of membrane-associated proteins?

A 
Transmembrane (intrinsic) - cross membrane, usually a-helix
Lipid associated (extrinsic) - bound to outer surface
Proteins attached to transmembrane protein - increase ionic strength to detach i.e. add NaCl
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82
Q

What are the 2 domains of membrane proteins?

A

Interdomain - intracellular

Outer domain - extracellular

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83
Q

What are some of the functions of membrane proteins?

A

Transporters, linkers, receptors, enzymes

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84
Q

Define enzyme

A

Proteins that catalyse biochemical reactions (biological catalysts)

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85
Q

Define active site

A

Parts of enzyme that react with substrate (+ cofactors) in reaction

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86
Q

Define co-enzyme

A

Small, diffusible organic residue that participates in enzyme catalysed reaction, is stable to heat

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87
Q

Define prosthetic group

A

Coenzyme covalently bound to enzyme so that not removed by dialysis

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88
Q

Define zymogen

A

Inactive precursor of enzyme

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89
Q

Define holoenzyme

A

Protein (apoenzyme) with coenzyme/ions required for activity

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90
Q

Define apoenzyme

A

Protein with coenzyme required for activity, liable to heat

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91
Q

Define substrate

A

Molecule on which enzyme performs a reaction

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92
Q

What is lysozyme?

A

An enzyme found in tissue fluids/secretions, tears, saliva, nasal mucus that protects against bacteria by causing cell to lyse and lose cell content

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93
Q

What is peptidoglycan?

A

Polysaccharide formed from polymerisation of monosaccharides N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)

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94
Q

Describe the structure of bacterial cell wall

A

Made of peptidoglycan - retains high internal osmotic pressure
Layers of repeating peptidoglycan units with peptide chain bound to NAM
Penta-glycine cross-links between last residue of chain and second last of opposite chain - added strength

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95
Q

Describe alpha and beta linkages

A

Alpha: H atoms of the C atoms in bond in cis formation
Beta: H atoms of C atoms in bond in trans formation

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96
Q

Describe the lysis of the cell wall

A

Lysozyme hydrolyses B1:4 bond (between C1 and C4) in glycan between NAG and NAM
Occurs rapidly at close to pH 7

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97
Q

What else will lysozyme hydrolyse?

A 
Oligo NAG (min 6 residues)
Fit into groove round enzyme that closes on the strand
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98
Q

What are serine proteases?

A

Enzymes with hyperactive serine residue at active site and appropriately spaced histidine and aspartate resides

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99
Q

Name some serine proteases

A

Trypsin
Chymotrypsin
Elastase
Thrombin

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100
Q

How do serine proteases work?

A

Catalyse by breaking peptide bond using charge relay system

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101
Q

Describe the charge relay system

A

Flow of electrons between 3 AAs making serine hyperactive

AAs are far apart in primary structure but close in 3D structure due to protein folding

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102
Q

Why are proteolytic enzymes secreted as zymogens?

A

As are hazardous to body so secreted as zymogens that are activated in gut lumen

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103
Q

Give examples of proteolytic enzymes

A

Pepsinogen
Tryspinogen
Chymotrypsinogen

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104
Q

Describe the activation of pepsinogen

A

Chief cells in gastric gland produce pepsinogen
Parietal cells produce HCl hydrolyses some peptide bonds to produce pepsin
Left over pepsinogen is hydrolysed again to produce more pepsin

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105
Q

Describe the activation of trypsinogen

A

Pancreatic duct secretes pancreatic zymogens
Some zymogens converted to trypsinogen which is converted to trypsin by enterokinase (produced by brush border)
Trypsin activates more enzymes such as chymotrypsinogen

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106
Q

Describe the activation of chymotrypsinogen

A

Inactive state: single polypeptide, 245AAs with 5 SS bridges, three portions of AS caN’T come together
Trypsin cuts bond between Arg15 and next residue - pi-chymotrypsin left
Cut at Leu13 removes dipeptide bond
Cut at Tyr146 and Asn148 removes another - a-chymotrypsin
3 parts held by SS bridges
Active site resides come together
Charge transfer complex with hyperactive serine formed

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107
Q

How is specificity of enzymes dictated?

A

Pocket close to AS into which an AA side chain may fit thus size and nature of pocket are important

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108
Q

Describe the specificity of trypsin, chymotrypsin and elastase

A

Trypsin: cuts basic R groups; Asp at bottom of pocket
Chymotrypsin: cuts hydrophobic R; hydrophobic pocket
Elastase: cuts small R; small pocket

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109
Q

Describe the steady state hypothesis

A

In enzyme catalysed reaction, enzyme and substrate form complex which is a transient state (either breaking down or reversing)
Initially conc. of complex will increase but will become steady as when broken down enzyme will form new complex

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110
Q

What is Vmax?

A

The velocity a reaction approaches as substrate conc. is increased

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111
Q

What is Michaelis constant (Km)?

A

Substrate conc. at 1/2Vmax
Dependent on substrate and enzyme
Measures affinity of enzyme for substrate - a high Km confers low affinity

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112
Q

What is the relationship between substrate conc. and velocity?

A

Michaelis-Menten equation
v = Vmax[S]/(Km+[S])

When [s]=Km v = 1/2Vmax
When [s]»Km v ~ Vmax

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113
Q

What is the importance of Km?

A

Can use to compare 1 enzyme’s affinity for different substrates or
Multiple enzymes affinities’ for 1 substrate

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114
Q

Describe hexokinase

A

Phosphorylates glucose
Widespread in tissue
Low Km = high affinity
Always active

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115
Q

Describe glucokinase

A

Found in liver and pancreas
High Km = low affinity only active at high glucose conc.
At high conc. glucose stored in liver as glycogen, insulin produced by pancreas

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116
Q

Explain the influencing factors of enzymes

A

Optimum temp. and pH range above optimum will denature and activity will suddenly drop
Increasing temp. increases energy of collisions, internal energy of reactants and number of collisions

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117
Q

What are lipids?

A 
Diverse class of insoluble compounds that don't form polymers
Are hydrophobic (mostly hydrocarbons) and soluble in organic solvents (ether, acetone, chloroform)
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118
Q

Give examples of lipids

A

Fats, oils, fatty acids, triacylglycerols, glycolipids, phospholipids, steroids

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119
Q

What is the main function of fatty acids?

A

Catabolised generating ATP or used to synthesise triglycerides and phospholipids

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120
Q

Main function of triglycerides?

A

Energy storage, protection, insulation

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121
Q

Phospholipids main function?

A

PM

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122
Q

Main function of steroids

A

Component of many hormones, cholesterol

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123
Q

Describe the structure of fatty acids

A

Long hydrocarbon chain with terminal carboxylic acid group
Hydrocarbon chain: saturated (no double bonds), monounsaturated (1 C=C), polyunsaturated (2+ C=C)

Unsaturation causes kink in chain
All naturally occurring unsaturated fats are in cis formation whereas trans unsaturated fats found in manufacture of food

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124
Q

Compare saturated and unsaturated fats

A

Palmitic (C16) is a saturated fat, MP 69.9
Oleic (C18) is monounsaturated, MP 13.4 - C=C makes packing of molecule difficult

Most animal fats are saturated whereas most fish and plant fats are unsaturated

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125
Q

What is glycerol and what is its importance?

A

Three C substance that forms backbone of fatty acids in fats

Important component of triglycerides and phospholipids

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126
Q

What is triglyceride and describe its structure

A

Main component of vegetable oil and animal fats formed from the esterification of 3 fatty acids with glycerol

Has chemical structure CH2COOHR-CHCOOHR’-CH2COOHR”; Rs are long alkyl groups
The fatty acids can be all same, different or 2 the same

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127
Q

What is the importance of triglycerides?

A

Metabolism: contain 2X energy as carbs and proteins
Storage and transport form of fats
High levels linked to atherosclerosis (heart disease, stroke)

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128
Q

What is the role of adipocytes and adipose tissue?

A

Adipocytes specialised for synthesis and storage of triglycerides
Found in subcutaneous layer and in abdominal layer
Subcutaneous fat provides insulation

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129
Q

What is lipolysis?

A

Breakdown of triglycerides into glycerol and fatty acids with release of energy
Fatty acids released into blood, circulate body

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130
Q

Describe the catabolism of glycerol

A

Converted to glyceraldehyde 3-P and then glucose OR enter TCA depending on ATP supply

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131
Q

Describe the catabolism of fatty acids

A

Enzymes remove 2C atoms at a time to acetyl CoA to enter TCA

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132
Q

Describe the process of FA activation

A

Acetyl-CoA synthases esterify long chain FAs to acyl-CoA

Is ATP dependant

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133
Q

Describe the process of FA oxidation

A

Acyl-CoA dehydrogenase removes H2 from acyl-CoA, NAD is reduced to NADH2, acetyl-CoA oxidised to trans-enoyl-CoA
enoyl-CoA hydratase, hydrates trans-enoyl-CoA to B-hydroxyacyl-CoA
B-hydroxyacyl-CoA dehydrogenase oxides B-..-CoA to B-ketoacyl-CoA
Acyl-CoAacetyl-transferase moves acetyl forming acyl-CoA (2Cs shorter) + acetyl-CoA

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134
Q

What is lipogenesis?

A

Synthesis of lipids (anabolism) from smaller units
Mainly occurs in liver and adipose tissue in conditions of excess sugar as glucose converted to glycogen
It doesn’t appear to be essential

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135
Q

Compare glucose and fructose

A

Glucose used in cells throughout body, fructose only in liver
Glucose converted to glycogen, some to FAs and triglycerides
Fructose converted to acetyl them FAs and triglycerides

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136
Q

What are essential fatty acids?

A

FAs that are required in human diet as humans lack specific enzyme so cannot be synthesised by the body

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137
Q

What can a deficiency of a-linoleic acid and linoleic acid lead to?

A

Dry scaly rash, decreased growth (children/infants), susceptibility to infection, poor wound healing

Present in variety of foods, represent omega 3 and 6 category of lipid structure

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138
Q

Describe the structure of phospholipids

A

2 FAs and P group attached to glycerol

FAs from hydrophobic tail, P and its attachment form hydrophilic head

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139
Q

What is meant by amphipathic?

A

Molecule with both hydrophobic and hydrophilic groups

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140
Q

Describe saturation in phospholipids

A

1 chain saturated, other not

Degree of saturation alters ability of molecules to pack, affects fluidity

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141
Q

What is the function of cholesterol?

A

Controls permeability of membrane

Makes membrane less flexible due to rigid steroid ring

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142
Q

Describe glycolipid structure

A

2 hydrophobic tails, hydrophilic region with 2+ sugar residues i.e. phospholipids without P

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143
Q

What is the function of glycolipids?

A

Make up 5% of outer monolayer
Sugar groups exposed on cell surface protect and modulate membrane function
Insulating agents in nerve cells (gangliosides)

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144
Q

Describe the structure of steroids

A

Lipids characterised by C skeleton of 4 fused rings

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145
Q

What is the role of steroids?

A

Cholesterol: high levels cause atherosclerosis
Hormones: testosterone, oestrogen, cortisol (synthesised from cholesterol) control metabolism, development of sexual characteristics, immune functions

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146
Q

What is a lipoprotein?

A

Biochemical assembly that contains both proteins and lipids

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147
Q

What is the function of lipoproteins?

A

Transport insoluble lipids in plasma

Non-polar lipids (triglycerides) contained in hydrophobic centre, polar lipids (phospholipids) form coat

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148
Q

What are apoproteins?

A

Protein components of lipoproteins

Interact with cellular receptors and determine the metabolic fate of lipoproteins

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149
Q

Explain LDL and HDL

A

LDLs carry FAs in blood for use by cells but also deposit on artery walls (bad)
HDLs carry LDLs away from artery walls (good)

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150
Q

What are some of the ways to treat hypercholesrerolemia?

A

Reduce intake (egg yolk, liver, oily fish)
Reduce absorption uptake - zetia, ezetro, niacin
Statins - block enzyme in synthesis of cholesterol

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151
Q

What are the 2 classifications of carbs?

A

Simple - monosaccharides

Complex - disaccharide, oligosaccharide(2+), polysaccharide (many)

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152
Q

Describe monosaccharides

A

Simple sugars: can’t be converted into smaller molecules by acid hydrolysis
1 sugar, usually colourless, water-soluble, crystalline solids
Building blocks of di and polysaccharides

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153
Q

Describe the structure of monosaccharides

A

Generally have formula (CH2)n - deoxyribose is an exception
Simple monosaccharides C4-7 called tetroses, pentoses, hexoses, heptoses
Exceptions in animals N-acetyl sugars (8C), sialic acid (9,10,11C)

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154
Q

What are 2 classifications of monosaccharides?

A

Aldose and ketose
Aldose - -CHO (aldehyde group)
Ketose - C=O (ketone group)
e.g. aldopentose or ketopentose

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155
Q

Describe the structure of glucose in both straight chain and ring

A 
C6H12O6
Is an aldose sugar i.e. has -CHO
Ring: C1 binds to C5 - C1-O-C5
O enables C atoms to bind to from ring
H from C5 OH binds to O on C1, C1 binds to O
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156
Q

Describe the structure of fructose

A

C6H12O6
Is a ketose i.e. has C=O on C2
Ring: C2 bonds to C5
H of C5 OH binds to O of C2, C2 binds to O on C5

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157
Q

What is stereochemistry?

A

Study of spatial 3D relations of atoms in molecules

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158
Q

What are Fischer projections?

A

Basic 2D drawing of 3D molecule
C1 is always at top
Projections drawn to left are ABOVE the ring
Projections to right are BELOW the ring

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159
Q

Explain D and L sugars

A

D and L sugars are optical isomers (mirror images of each other)
D and L refer to the absolute configuration of asymmetric C furthers away from aldehyde/ketone group OR if OH falls on either LHS/RHS
D-glucose is biologically active, OH of C5 falls on RHS

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160
Q

What is the structure of D-glucose?

A

OH of C2,4,5 to right
OH of C3 to left

L-glucose is opposite

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161
Q

What happens in solution of glucose in terms of structure?

A

Equilibrium favouring ring form established
Ring formation creates new chiral centres - C1 in aldoses, C2 in ketoses
This increases the number of possible isomeric forms

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162
Q

What are isomers of D-glucose called?

A

Anomers

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163
Q

Describe the 2 anomers of D-glucose

A

Alpha - (new) OH of C1 is TRANS to CH2OH on C5

Beta - OH of C2 is CIS to CH2OH on C5

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164
Q

What is mutarotation?

A

Interconversion between anomer stereoisomers

Different anomers have different optical rotations

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165
Q

What are monosaccharide derivatives?

A

Simple sugar molecules which contain functional groups as well as OH, either CHO/CO, vary from empirical formula

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166
Q

Describe deoxy derivatives

A

OH replaced by H

e.g. deoxyribose sugar - ribose with OH on C2 replaced by H

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167
Q

Describe sugar acid derivatives

A

OH group oxidised to COOH

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168
Q

Describe sugar alcohol derivatives

A

CO (aldehyde or ketone) reduced to primary/secondary OH

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169
Q

Describe phosphorylated sugars

A

P group attached

Alcoholic group esterified with phosphoric acid

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170
Q

What are amino sugars?

A

Sugar with primary amine group replacing OH

e.g. glucosamine precursor for GAGs (major component of joint cartilage) thus used to treat osteoarthritis

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171
Q

Explain the formation of disaccharides

A

Aldehyde/ketone group reacts with molecules own OH to form ring, then link to C bearing OH on another sugar molecule creating a disaccharide

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172
Q

How are monomers linked?

A

Glycosidic bonds formed when anomeric OH group condenses with alcohol of second monosaccharide
Catalysed by hydrolyse (dehydration) to form R-O-R link

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173
Q

Describe the structure of sucrose

A

Glucose and fructose monomers linked by alpha 1,2 linkage

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174
Q

What is glycogen?

A

Polysaccharide that is the principal storage form of glucose found as granules in cytosol
Liver cells have highest conc. but muscles have greater total amount

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175
Q

Describe the structure of glycogen

A 
Highly branched (increases packing)
Linear chains of glucose connected by a-1,4 glycosidic linkages with branches attached through a-1,6 links every 10 residues
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176
Q

What 2 enzymes are required for glycogen degradation and why?

A

Glycogen phosphorylase to hydrolyse a-1,4 linkages but can only work on linear chains OR a-amylase (digestive)
Debranching enzyme to hydrolyse a-1,6 links to straighten out chain

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177
Q

Describe the degradation of glycogen

A

Glycogen phosphorylase breaks glycogen into glucose-1-P but is halted 4 residues from branching point
Glycogen debranching enzyme transfers trisaccharide to a-1,4 adjacent a-1,4 link leaving single glucose molecule at a-1,6
GDE hydrolyses remaining glucose molecule so glycogen phosphorylase can continue

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178
Q

Describe the structure of starch

A

(C6H10O5)n
2 polysaccharides monomers: amylose, amylopectin
Amylose: glucose monomers linked by a-1,4 links
Amylopectin: coiled structure, like glycogen but a-1,6 branch every 24-30 residues

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179
Q

What is the function of starch?

A

Digested by hydrolysis, catalysed by amylases, back to sugar monomers which can be broken down to glucose for energy

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180
Q

What is cellulose?

A

Polymeric polysaccharide of B-glucose monomers

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181
Q

What is the function of cellulose?

A

Primary structural component of cell wall of green plants
Lignin and cellulose (lignocellulose) most common biopolymer on earth
Only tunicates evolved the ability to create and use cellulose
Indigestible by humans so acts as hydrophilic bulking agent for faeces

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182
Q

Describe the structure of cellulose

A

Layered linear chains of B-1,4 linked D-glucose units packed into crystals (myofibrils)
Layers linked by H bonds

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183
Q

What is lactose?

A

Disaccharide of B-D-galactose and B-D-glucose linked through B-1,4

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184
Q

What are glycosaminoglycans? (GAGs)

A

Large, pure carbohydrates that are -ve charged, hydrophilic

Polysaccharides present on animal cell surface and in ECM

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185
Q

Describe the structure of GAGs

A

Disaccharide repeating unit containing glucosamine or galactosamine and uronic acid
At least one of the sugars has a -ve charged carboxylate or sulphate group - with exception of hyaluronic acid (no sulphate group)

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186
Q

What is a glycoprotein?

A

Macromolecule composed of protein and a carbohydrate which is added in posttranslational modification either at asparagine (N-glycosylation) or hydroxylysine/hydroxyproline/serine/threonine (O-glycosylation)

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187
Q

What is the function of glycoproteins?

A

Assist protein folding or improve stability
Immune cell recognition: antibodies (immunoglobulins) interact directly with antigens, moles of major histocompatibility complex (MHC) surface of cells interact with T-cells (adaptive immune response)

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188
Q

Explain N and O glycosylation

A

Glycosylation is the attachment of carbohydrate to AA side chain
N: attach to N of amide side chain (asparagine)
O: attach to O of OH side chain (hydroxylysine/hydroxyproline/serine/threonine)

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189
Q

What are proteoglycans?

A

Heavily glycosylated glycoproteins - core protein with several GAG chains

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190
Q

What are the functions of GAGs?

A

Structural: ECM and BM
Space-filling in cartilage
Modifiers/activators of effector proteins (growth factors, proteases)

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191
Q

What are the functions of proteoglycans?

A

Form large complexes in ECM with proteoglycans and fibrous matrix proteins (collagen)
Binding of cations and water
Regulation of movement of molecules through matrix

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192
Q

What is chondroitin sulphate?

A

Sulphate GAG composed of N-acetyl-galactosamine and glucuronic acid
Usually forms part of a proteoglycan

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193
Q

What is the function of chondroitin sulphate?

A

Major structural component in cartilage conferring resistance to compression
Dietary supplement for treatment of osteoarthritis

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194
Q

What is heparin?

A

Highly sulphated GAG used as injectable anticoagulant and used for inside of test tubes, renal dialysis machines

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195
Q

Describe the structure of peptidoglycan

A

Crystal lattice of linear chains of NAG and NAM
Each NAM has peptide chain usually containing AAs that do not occur in humans thought to protect against attacks by most peptidases

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196
Q

Describe the energy balance in humans

A

Balance between energy intake and energy expenditure

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197
Q

Describe the anabolism of glucose

A

Glucose enters cell, undergoes glycogenesis forming glycogen in liver and muscle cells
OR undergo lipogenesis and join FA chain

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198
Q

Describe the anabolism of FAs

A

FAs esterified to triglycerides in adipose tissue

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199
Q

Describe the anabolism of AAs

A

AAs undergo protein synthesis to form proteins in muscle

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200
Q

Describe the metabolism of glycogen

A

Glycogen undergoes glycogenesis forming glucose, undergoes glycolysis to pyruvate converted to acetyl-CoA enters TCA

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201
Q

Describe metabolism of triglycerides

A

Undergo lipolysis forming FAs, undergo B-oxidation to form acetyl-CoA enter TCA

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202
Q

Describe protein metabolism

A

Proteolysis converts to AAs either directly enter TCA or converted to acetyl-CoA

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203
Q

Describe glycogen stores and their mobilisation

A

In liver glycogen converted to glucose-6-P which is converted to glucose which can enter brain or back to glucose-6-P and used by muscles to produce lactate
Muscle cells produce glucose 6P then lactate

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204
Q

Describe the cori cycle

A

Lactate produced in muscle cell converted to pyruvate which can enter gluconeogensis to re-form glucose which can be recycled

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205
Q

Describe lipid stores and mobilisation

A

Triglyceride stored in adipose broken down to glycerol and FAs
Glycerol undergoes gluconeogenesis forming glucose, enters brain
FAs enter muscle or undergo ketogenesis forming ketone bodies utilised by brain or enter muscle

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206
Q

Describe protein utilisation

A

Undergo proteolysis produce AAs which can enter TCA, converted to Acetyl-CoA or undergo transamination (amino group moved)
Acetyl-CoA enter TCA or converted to ketone bodies
After transamination form pyruvate either enter TCA or gluconeogenesis

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207
Q

Describe glucose transport

A

Enters cells via facilitated diffusion by GLUTs

Uptake increased by increasing GLUTs in PM - insulin or exercise

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208
Q

Describe FA transport

A

Thought to diffuse across PM or may involve FA transporter proteins

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209
Q

How is energy stored in cells?

A

In chemical bonds

When cell has enough energy available it stores it by adding Pi group to ADP forming ATP

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210
Q

What are the stages of ATP production?

A

Digestion
Glycolysis
TCA

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211
Q

Describe digestion

A

Food stuff digested
HCl in stomach
Enzymes - mouth, stomach, small intestine
Enzymes in lysosomes for internal cell digestion

Absorption through cells in SI, enter bloodstream then cells

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212
Q

Describe glycolysis

A

Starts in cytoplasm
Glucose broken down to 2 pyruvate molecules
2ATP and NADH produced per pyruvate
Pyruvate molecules move to mitochondria where converted to CO2 and 2C acetyl group which attaches to CoA

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213
Q

Describe the structure of CoA

A

8 trimers of lipoamide reductase-transacetylase
6 dimers of dihydrolipoyl dehydrogenase
12 dimers pyruvate decarboxylase

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214
Q

What are the functions of the three enzymes in CoA?

A

Pyruvate decarboxylase - removes CO2
Lipoamide reductase transacetylase - transfer acetyl group
Dihydrolipoyl dehydrogenase - reduces NAD

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215
Q

What happens in glycolysis in anaerobic conditions?

A

Fermentation
Muscle: pyruvate reduced to lactate reforming NAD+
Yeast: pyruvate reduced forming CO2 and acetaldehyde which is reduced to ethanol reforming NAD+

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216
Q

Describe stage 3 of ATP production

A

Acetyl group enters TCA where it is oxidised to CO2 and large amounts of NADH generated
NADH passed along electron transport chain where energy released produces ATP and consumes O2

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217
Q

What is oxidative phosphorylation?

A

ATP formation driven by transfer of electrons from food molecules to molecular O2
Electron ends up on O2, with H+ H2O formed

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218
Q

Name the 4 complexes of the electron transport chain

A
  1. NADH dehydrogenase
  2. Succinate dehydrogenase
  3. Coenzyme Q reductase
  4. Cytochrome c reductase
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219
Q

What are the roles of the complexes in electron transport chain?

A

NADH dehydrogenase, succinate dehydrogenase, coenzyme Q reductase pump protons across membrane into intermebrane space making intermembrane increasing acidic
Cytochrome c reductase give electron to O2 producing H2O

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220
Q

How does the electron transport chain produce ATP?

A

Due to the high H+ conc. in intermembrane space, protons diffuse down conc. gradient through ATP synthase producing lots of ATP

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221
Q

Name and describe the inhibitors of electron transport chain

A

Rotenone: blocks NADH from being oxidised by NADH dehydrogenase
Antimycin A: blocks complex 2
CN or CO: prevent O2 being reduced by cytochrome c reductase

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222
Q

What is the role of reactions?

A

Create order within cells: smaller molecules used to make macromolecules

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222
Q

Define catabolism and anabolism

A

Catabolism: break down of molecules releasing energy
Anabolism: construction of complex molecules from simple ones, storage of energy

223
Q

Define free energy

A

Gibbs free energy (G): measure of energy contained in a molecule due to vibration, rotation, bonds

224
Q

What is delta G?

A

Changes/difference in free energy

DG = G(products p) - G(reactants)

225
Q

Define exergonic and endergonic

A

Exergonic: releases energy to surroundings -DG
Endergonic: absorbs free energy +DG

226
Q

Define activation energy

A

Energy difference between reagents and transition state i.e. energy required for reaction to progress

227
Q

How do enzymes work in terms of EA?

A

Lower the EA allowing larger proportion of random collisions with surrounding molecules to push substrate over EA

228
Q

How do enzymes work?

A

Bind substrate tightly holding it in a way that facilitates conversion to product

229
Q

Explain coupled reactions

A

Favourable (oxidisation of glucose) reactions release energy which is captured in chemical form and used to power unfavourable reactions (forming peptide bond)
Favourable reactions take place spontaneously whereas unfavourable only occur if coupled

230
Q

What are carrier molecules?

A

Small proteins that contain 1+ energy-rich covalent bond and diffuse rapidly throughout cell thus carry bind energy from generation to utilisation

231
Q

How do carrier molecules (coenzymes) store their energy?

A

In easily transferable groups/high-energy electron (easily oxidised/reduced) - ATP, NADH, NADPH

232
Q

Describe the synthesis of a polynucleotide

A

Nucleoside monophosphate activated by sequential transfer of terminal P from 2 ATP
High energy intermediate (nucleoside triphosphate) exists freely until reacts with growing end of R/DNA releasing pyrophosphate
Hydrolysis of pyrophosphate to Pi highly favourable, drives overall reaction

233
Q

Explain the limits of ATP

A

DG of ATP is -7.3kcal/M only drive reaction up to that amount
If reaction requires more ATP hydrolysis altered to produce AMP and PPi (pyro) which is hydrolysed producing large amounts of free energy

234
Q

What is the importance of enzyme inhibitors?

A

Info about shape of AS and AA residues at AS
Info about chemical mechanism
Info about regulation/control of metabolic pathway
Aide drug design

235
Q

What are the 2 broad classifications of inhibitors?

A

Reversible
Irreversible: usually involves formation or breaking of covalent bonds - enzyme forms covalent bond with AS so cannot be removed

236
Q

What are the 3 types of reversible inhibitors?

A

Competitive
Non-competitive
Uncompetitive

237
Q

Explain irreversible inhibition

A

Inhibitor forms covalent bond with AS of enzyme so is permanently attached thus permanently inactivates enzyme
e.g. diisopropylphosphofluoridate prototype for nerve gas sarin, permanently inactivates serine proteases

238
Q

Explain competitive inhibition

A

Inhibitor competes with substrate to bind on AS
Inhibitor and substrate have similar structures
ONLY binds to enzyme NOT ES complex

239
Q

Explain the effect of competitive inhibitors on Vmax and Km

A

Reduces amount of free enzyme available for substrate binding (forms EI complex) thus Km increased, Vmax unchanged but requires more substrate to reach

240
Q

Give an example of competitive inhibition

A

Succinate is converted to fumarate by succinate dehydrogenase
Malonate is a competitive inhibitor for this reaction

241
Q

How is competitive inhibition reversed?

A

Increase conc. of substrate to overcome reduced affinity

242
Q

Explain non-competitive inhibition

A

Inhibitor binds to separate, distinct binding site causing SLIGHT conformation change
Can bind to E or ES and from ESI complex which is inactive

243
Q

Explain the effect on Vmax and Km of non-competitive inhibition

A

As substrate can still bind Km remains constant

As ESI inactive Vmax reduced

244
Q

Give an example of non-competitive inhibition

A

Fructose-1,6-diphosphate converted to fructose-6-phosphate by fructose-1,6-bisphosphatase which is inhibited by AMP (binds to separate site) and no fructose-6P produced

245
Q

Explain uncompetitive inhibition

A

Binding of substrate allows inhibitor to bind forming inactive ESI complex
Inhibitor ONLY binds to ES

246
Q

Explain the effect of uncompetitive inhibition on Vmax and Km

A

Vmax decreased as enzyme inhibited

Km also reduced as creates better ES binding as only binds to ES (due to equilibrium and Le Chatelier’s Principle)

247
Q

What are allosteric modulators?

A

Substances which can regulate enzyme activity

248
Q

Explain the 2 types of allosteric modulators

A

Positive: increase enzyme activity, binds to allosteric site causing conformational change to enhance substrate binding
Negative: decrease activity, binds to site causing conformational change to decrease substrate binding

249
Q

What 2 hormones are responsible for regulation of glucose levels?

A

Insulin: promotes uptake and conversion to glycogen
Glucagon: promotes breakdown of stored glycogen to glucose

250
Q

Name the 2 conditions caused by excess and lack of glucose

A

Hyperglycaemia: excess glucose, hallmark of diabetes, glucosuria (glucose toxicity)
Hypoglycaemia: lack of glucose, loss of cognitive function, coma, permanent brain damage

251
Q

How is glucose transported into cells in the body?

A

Intestine: uptake from lumen to epithelial requires active transport
Body: blood to cells (muscle, liver, adipose) passive or facilitated diffusion

252
Q

How is glucose uptake mediated?

A

GLUT transporters mediate glucose transport into liver, adipose, muscle tissues

253
Q

Describe GLUTS 1-4

A

GLUT1+3: PM throughout body, low Km 1mM (high affinity), maintain basal blood glucose 3-6mM
GLUT2: liver, pancreatic cells, high Km 15-20mM, (low affinity as liver stores, pancreas produces insulin in high conc)
GLUT4: muscle, adipose, low Km, insulin sensitive (phosphorylated by Metformin (anti-diabetic) increasing insulin sensitivity)

254
Q

How is glucose uptake regulate by insulin and exercise?

A

Uptake into muscle and adipose increased by insulin which increases no. of GLUT4 transporters in PM (GLUT4 containing vesicles fuse with PM)
Insulin resistance associated with fewer GLUT4 transporters
Exercise recruits GLUT4 transporters to PM in muscle

255
Q

Describe the alternative fates of glucose

A

Converted to glucose-6P either enter pentose phosphate pathway produce 5C sugar OR glycolysised to pyruvate (gluconeogenesis reproduce glucose-6P)

256
Q

Explain the role of hexokinase in glycolysis

A

Found in most cells throughout body, phosphorylates glucose to glucose-6P (1st step of glycolysis)
Low Km
Allosteric inhibition by own product (glucose-6P)
Inhibition of HK causes increase in intracellular glucose inhibiting GLUT transporter

257
Q

Explain the role of glucokinase in glycolysis

A

Phosphorylates glucose in liver and pancreatic B cells
Higher Km - only active when glucose levels are high
In B cells acts as glucose sensors for insulin secretion
Not inhibited by glucose-6P

258
Q

Outline the 10 steps of glycolysis

A 
G-glucose
G-glucose-6P
F-fructose-6P
F-fructose-1,6-bisphosphate
G-glyceraldehyde-3P (+ dihydroxyacetone-P)
G-glyceraldehyde-3P
B-1,3-bisphosphoglycerate
P-3-phosphoglycerate
P-2-phosphoglycerate
P-phosphoenolpyruvate
P-pyruvate
H-hexokinase
P-phosphoglucose isomerase
P-phosphofructokinase
A-aldolase
T-triosephosphate isomerase
G-glyceraldehyde-3P dehydrogenase
P-phosphoglycerate kinase
P-phosphoglycerate mutase
E-enolase
P-pyruvate kinase
259
Q

Explain how phosphofructokinase 1 regulates glycolysis

A

High ATP conc. allosterically inhibits PFK1 by binding, promotes tense conformation with low affinity for fructose-6P
PFK2 convert fructose-6P to fructose-2,6-bisP (+ ADP) high levels of fructose-2,6-bisP relieves inhibition
High levels of citrate (1st intermediate TCA) inhibits as confers ATP already present
ADP, AMP(extensive ATP hydrolysis) relieve inhibition

260
Q

Define kinases and mutases

A

Kinase: phosphorylates i.e. transfers PO4 from ATP to substrate
Mutase: transfer PO4 from 1C to another within molecule

261
Q

Describe fermentation

A

Anaerobic organisms lack respiratory chain, NADH reoxidised as pyruvate converted to more reduced compound

Some organisms convert pyruvate to ethanol oxidising NADH in reaction catalysed by alcohol dehydrogenase

262
Q

Explain how NADH enters the matrix of mitochondria

A

Oxaloacetate reduced to malate oxidising NADH
Malate enters matrix is oxidised to oxaloacetate reducing NAD+
Oxaloacetate converted to aspartate by glutamate forming a-ketoglutarate
Aspartate leaves matrix, reacts with a-ketoglutarate reforming oxaloacetate and glutamate

263
Q

Describe galactose metabolism

A

Gladstone phosphorylated to galactose-1P by galactokinase
UDP-glucose reacts with galactose-1P converting to glucose-1P and forming UDP-galactose
Glucose-1P P group moved by phosphoglucomutase to glucose-6P

264
Q

What is the importance of Ca?

A

Bone: provide structural integrity of skeleton

Biochemical processes: neuromuscular excitability, blood coagulation, hormonal secretion, enzymatic regulation

265
Q

Why must Ca conc. be maintained?

A

As has role in so many processes extra and intracellular conc. must be maintained

266
Q

Describe the regulation of intracellular [Ca]

A

Stored in mitochondria and ER
‘Pump-leak’ transport system: Ca leaks into cytoplasmic compartment, actively pumped into storage sites in organelles to shift away from cytosolic pools

267
Q

What are the 3 fractions of Ca in serum?

A

Ionised - 50%
Protein-bound - 40%
Complexed to serum constituents - 10%

268
Q

What protein is the majority of protein-bound Ca bound to?

A

Albumin -90%, binding is pH dependent

Rest is bound to globulins

269
Q

What 2 molecules is Ca complexed to?

A

Citrate

Phosphate

270
Q

Describe the effect of acute alkalosis on Ca binding

A

Inc. Ca binding, dec. ionised Ca

Causes inc. neural excitability and prone to seizures due to low ionised Ca in ECF causing inc. permeability to Na+

271
Q

Describe Ca turnover

A

1000mg intake
350mg absorption to ECF (1000mg) and exchangeable pool (4000mg)
500mg used and retrieved in bone remodelling
1000000mg stored in skeleton
200mg excreted in urine
150mg secreted into gut
800mg excreted in faeces

272
Q

What factors determine the conc. of serum Ca?

A

Intestinal absorption, renal excretion, bone remodelling

273
Q

Explain +ve and -be Ca balances

A

+: intestinal Ca absorption exceeds urinary excretion, difference deposited in growing bones
-: intestinal absorption less than urinary excretion

274
Q

What are the 3 hormones involved in regulating Ca homeostasis?

A

Calcitonin
Parathyroid hormone
Calcitriol

275
Q

How does calcitonin work and what is its effect?

A

Gs-couple: inc. cAMP, inhibit osteoclast, less Ca resorption, more Ca incorporated into bone tissue
Dec. Ca2+
Stimulated by inc. Ca2+ in plasma

276
Q

What is the function of PTH and what are its actions?

A

Inc. Ca

Inc. bone resorption
Inhib. renal P reabsorption in proximal tubule - excreted in urine
Inc. renal Ca reabsorption in distal tubule
Inc. intestinal Ca absorption indirectly by stimulating production of 1,25-dihydroxycholecalciferol

277
Q

What is the function of calcitriol?

A

PTH-like effect in bone

Mediated effects of PTH absorption of Ca and P by gut

278
Q

Where is calcitonin formed and secreted?

A

Parafollicular cells of thyroid

279
Q

Where is PTH formed and secreted?

A

Parathyroid gland

280
Q

How is the secretion of PTH regulated?

A

Negative feedback: secreted as serum Ca2+ falls

281
Q

How is VitD synthesised?

A
  1. Skin cells convert 7-dehydrocholesterol to pro hormone cholecalciferol (B3) using sunlight
  2. Liver then kidney convert pro hormone to active VitD3 (1,25-dihydroxycholecalciferol/dihydroxy-D3)
282
Q

What are the actions of VitD3?

A
  1. Inc. intestinal Ca absorption
  2. Inc. intestinal P absorption
  3. Inc. renal reabsorption of Ca and P
  4. Inc. resorption of bone
283
Q

What are osteomalacia/rickets?

A

Conditions caused by VitD deficiency leasing to poor bone mineralisation reducing bone mass thus making bones weak

284
Q

What are the 2 types of osteomalacia?

A

VitD-responsive

VitD-resistant

285
Q

Describe VitD responsive osteomalacia

A

Caused by deficiency in dietary intake of VitD precursors, inadequate sunlight exposure, malabsorption of Ca

286
Q

Describe the 2 forms of VitD-resistant osteomalacia

A

Pseudo-VitD: end-organ hyposensitivity

Hereditary VitD-resistant rickets: VitD receptor has poor affinity for its DNA due to mutation in the DNA binding domain

287
Q

What is osteoporosis and what are the 2 types?

A

Dec. in bone strength

Primary: post menopause lose bone rapidly; calcitonin treatment as slows bone resorption
Secondary: caused by corticosteroids, Cushing’s syndrome, immobilisation, GI disease, alcohol, age
senile due to dec. 1,25-dihydroxy-D3 secretion, dec. PTH levels

288
Q

Explain the evidence showing DNA is heredity genetic material

A

Virulent lysates contain inheritance materials that transformed harmless bacteria to virulent bacteria killing mouse
Protein/RNA digestion (protease, ribonuclease) didn’t destroy inheritance material - mouse died
DNA digestion destroyed inheritance material preventing bacterial transformation thus mouse lived

289
Q

Describe the structure of DNA

A

Linear polymer of 4 nucleotides - adenine, thymine, guanine, cytosine - each made of base, phosphate group and deoxyribose sugar
Nucleotides are linked by phosphodiester bonds and antiparallel strands held in double helix by H bonds between complementary base (AT, GC)

290
Q

What are the 3 DNA conformation?

A

B A Z

B most prominent but flexible nature of helix allows A Z conformations

291
Q

What is the Central Dogma Theory?

A

Specific DNA gene sequence gets transcribed into RNA, then translated into unique proteins

292
Q

Describe the process of DNA replication

A
  1. Helicase unwinds double helix forming replication fork
  2. Single-stranded DNA binding proteins stabilise SSDNA to prevent rebinding to double helix
  3. RNA primase synthesises short fragments of RNA primer required for initiation of DNA synthesis by DNA polymerase 3
  4. DNA polymerase 1, DNAse H replace RNA primers with DNA
  5. DNA ligase joins Okazaki fragments (lagging strand) to create continuous newly synthesised DNA
293
Q

What are genes?

A

Basic unit of heredity in all living organisms

294
Q

What is the function of genes?

A

Encode for proteins essential for biological functions and structures
Some produce non-coding RNA molecules that play role in protein biosynthesis and gene regulation

295
Q

What are the molecules that result from gene expression called?

A

Gene products

296
Q

How do cells read the genome?

A

DNA doesn’t direct protein synthesis directly, use RNA intermediate used as template for protein synthesis
Central Dogma of molecular biology

297
Q

Compare DNA and RNA

A

Sugar: DNA - deoxyribose; RNA - ribose
Bases: ATGC; AUGC
Structure: double stranded helix; single strand (siRNA is double)

298
Q

Describe the process of transcription

A
  1. Small portion of DNA unwound
  2. Only 1 of DNA strands acts as RNA template
  3. RNA chain produced called transcript
  4. RNA polymerase catalyses formation of phosphodiester bonds, moves stepwise along DNA, unwinding DNA helix to expose new region
  5. Extended 1 nucleotide at a time in 5’-3’ direction
299
Q

What is the significance of the direction of RNA polymerase?

A

Determines which DNA strand will be used as template as only work in 5’-3’ direction

300
Q

Name and describe the role of the main transcription factors (TF)

A

TFIID + TBP: binds TATA-box in promoter region near imitation site
TFIIA/B: binds TFIID/TBP forming complex for RNA polymerase to bind
RNA polymerase: initiates transcription of RNA from DNA, requires ATP

301
Q

What are the 2 types of RNA?

A

Coding - 4% (mRNA)

Functional - 96%

302
Q

What are the 6 types of functional RNA?

A

rRNA: component of ribosomes where protein synthesis occurs
tRNA: carry AAs to ribosomes
Small nuclear: splice hnRNA to mRNA
Small nucleolar: chemical modification of rRNA
Micro + short interfering: regulate gene expression in eukaryotic cells

303
Q

What are the types of post-transcriptional RNA processing?

A

End-modification
Splicing
Cutting
Chemical modification

304
Q

How is pre-mRNA converted to mRNA?

A

snRNPs bind to intron forming loop that pulls exons together

Intron loop is excised and exons spilled together forming mature mRNA

305
Q

What is mRNA translation?

A

Conversion of info. in mRNA into protein

306
Q

What are the rules of the genetic code?

A

Sequences of nucleotides in mRNA read in codons (groups of 3) each specifying an AA or stop signal

307
Q

Define what is meant by degenerate

A

Many codons are redundant as encode the same AA

308
Q

What is the binding of AAs dependent on?

A

tRNAs that recognise and bind both to codon (via complementary anticodon) and to AA

309
Q

How does the AA bind to tRNA?

A

Short, single-stranded 3’ region of tRNA ribose binds to carboxyl end of AA forming ester bond

310
Q

What is the recognition and binding of correct AA dependent on?

A

Aminoacyl-tRNA synthetase

Covalently couples each AA to appropriate tRNA molecule

311
Q

How are ribosomes formed?

A

Ribosomal proteins synthesised in cytoplasm, transported back to nucleolus to bind with rRNA subunit and exported back to cytoplasm

312
Q

Describe the structure of ribosomes

A

1 small subunit, 1 large subunit

Small: provides framework on which tRNA anticodons accurately matched to mRNA codons
Large: catalyses formation of peptide bonds linking AAs

313
Q

What is the function of ribosomes?

A

Maintain the correct reading frame and ensure accuracy

314
Q

What are the 4 binding sites of ribosomes?

A
  1. mRNA
  2. Aminoacyl (A): tRNA with bound AA
  3. Peptidyl (P): tRNA attached to growing peptide chain
  4. Exit (E)
315
Q

Describe the process of protein synthesis

A
  1. Ribosome subunit join near 5’ end of mRNA
  2. tRNA anticodon binds to complementary mRNA codon at A site bringing AA
  3. Ribosome moves towards 3’ end, at P site peptide bond forms between existing polypeptide and new AA
  4. mRNA moves 1 codon along through small subunit, tRNA ejected at E site, A site free again
316
Q

What is the start codon of protein synthesis?

A

AUG which special tRNA binds to with methionine - distinct from usually methionine tRNA

317
Q

What is the importance of the start codon?

A

Dictates reading frame for whole protein
Error can lead to frame shift mutation where reading frame is shifted causing all codons to be translated incorrectly forming non-functional protein

318
Q

What are the stop codons and how do they work?

A

UAA, UAG, UGA

Signal binding of release factor
Forces peptidyl transferase to bind water freeing carboxyl end of peptide that keeps peptide in ribosome
Released into cytoplasm

319
Q

Define somatic and reproductive division

A

Somatic: cells of body reproduce themselves
Reproductive: body produces gametes

320
Q

What is the function of somatic division?

A

Process by which body grows and replaces dead/damaged cells

321
Q

What is the feel cycle?

A

Orderly sequence of events in which the cell: duplicates its contents, divides

322
Q

Why must contents must be duplicated for the CC?

A

So genes can be passed onto next generation

323
Q

What are the 2 major phases of the CC?

A

Interphase: not diving

Mitotic phase: diving

324
Q

What is interphase?

A

State of high metabolic activity during which cell does much frowning and replicates DNA and organelles/proteins

325
Q

What are the 3 stages of interphase and state what happens during them

A

G1: replicates organelles and cytosol
S: DNA replication
G2: enlarges, synthesises enzymes and proteins for mitosis

326
Q

What is the G0 phase?

A

Phase most cells are in

If exit cell cycle enter G0, usually cannot re-enter

327
Q

What are the 2 stages of the mitotic phase?

A

Mitosis: nuclear division
Cytokinesis: cell division

328
Q

What are the 4 phases of mitosis and what happens during each?

A

Prophase: chromatin condense to paired chromatids, nucleolus and nuclear membrane disappear, centrioles move to opp. poles
Metaphase: chromatids line up on metaphase plate
Anaphase: identical sets of chromosomes move to opp. poles
Telophase: nuclear envelope and nucleoli re-appear, chromosomes resume chromatin form

329
Q

When does cytokinesis occur and what happens?

A

In late anaphase
Contractile ring forms cleavage furrow around centre of cell
Cytoplasm divided into 2 equal portions

330
Q

What are cyclins and Cdks?

A

Cyclins are regulatory proteins that activate Cdks

Rb tumour suppressor gene is the major target of Cdks which they phosphorylate at multiple points throughout CC

331
Q

What is meant by G1 restriction point being the ‘point of no return’?

A

Once cell proceeds through point it will complete CC including mitosis and cytokinesis

332
Q

How can inhibitors block the CC?

A

Inhibitors of Cdk4 (INK4 protein) can prevent phosphorylation of Rb

333
Q

Define hypertrophy and give examples of chronic hypertrophy

A

Increase in size of cell without division
Cirrhosis of liver: hepatocytes become swollen causing narrowing of sinusoids

Heart conditions: cardiac myocytes hypertrophy in response to excessive workload

334
Q

What is atrophy?

A

Decrease in size/number of cells and subsequent decrease in size of tissue/organ
Cachexia seen in HIV and cancers

335
Q

Define hyperplasia and give example of chronic

A

Increase in no of cells due to inc. in cell division

Psoriasis in skin
Make prostate may lead to benign or malignant tumour

336
Q

What is a cancer?

A

Cells that divide without control

Usually associated with loss of tissue differentiation and function (anaplasia)

337
Q

What are tumours?

A

Swelling or lesion formed by abnormal cells

May be cancerous (malignant) and usually spread to other organs (metastasis)

338
Q

How does epidermal growth factor regulate cyclin D1 production?

A
  1. EGF binds receptor, activates G protein
  2. kinase cascade will phosphorylate AP1 transcription factor through jun subunit
  3. TF binds promoter region of cyclin D1 causing transcription of cyclin D1
339
Q

Define glycolysis

A

Breakdown of glucose to 2 pyruvate and ATP molecules

340
Q

Define glycogenesis

A

Assembly of glycogen from excess glucose

Requires ATP, initiated by insulin

341
Q

Define glycogenolysis

A

Breakdown of glycogen to glucose

Regulated by glucagon

342
Q

Define gluconeogenesis

A

Synthesis of glucose from metabolites (lactate, pyruvate, glycerol, alanine)

343
Q

What are Islets of Langerhans?

A

Highly vascularised endocrine glands in the pancreas

High vascularisation allows hormones ready access to circulation

344
Q

What are the 4 secretory cells of the Islets?

A

a: glucagon
B: insulin
Delta
Digamma

345
Q

What are the functions of insulin?

A

Regulate blood glucose: signals liver, muscles, adipose to take up glucose; aides cells taking up for energy
Signal storage of Glc as Gly when in excess

346
Q

Describe the synthesis of insulin

A
  1. Leader sequence cleaved leaving proinsulin made of A,B,C domains
  2. Proteases cleave proinsulin in 2 places releasing peptide C and mature insulin (A,B joined by S-S bond)
  3. Packaged into secretory granules containing equimolar amounts of insulin and peptide C
  4. Released into extracellular space during secretion
347
Q

Describe the 7 steps of insulin release

A
  1. Glc enters via GLUT2
  2. Inc. influx inc. Glc metabolism, inc. [ATP]i
  3. Inc. [ATP]i inhib. KATP channel
  4. Closed KATP causes depolarisation
  5. Depolarisation activates VGCa2+C in PM
  6. Influx of Ca2+, inc. Ca2+ induces Ca2+-induced Ca2+ release
  7. Ca2+ leads to exocytosis, releasing secretory granules
348
Q

What are the 3 chemical controls of insulin release?

A

AAs: stim. (inc. uptake and protein synthesis)
Keto acids: stim. (inc. uptake to prevent lipid and protein utilisation)
Glucose: stim. (feedback loop)

349
Q

What hormones are B cells sensitive to?

A

Glucagon - inhib.

Somatostatin - inhib

350
Q

Describe the neuronal control of insulin release

A

PSNS: ACh stim
SNS: NA inhib

351
Q

Describe the stim. of Glc disposal postprandial

A

Insulin binds receptor
Insulin signalling pathway activates: effects on protein metabolism, effects on growth, effects on lipid metabolism and translocation of GLUT4 containing vesicles to PM
Inc. Glc uptake

352
Q

Describe the inhib. of Glc production postprandial

A

Insulin blocks Glc production via glycogenolysis and gluconeogenesis
PEPCK (inhib gluconeogenesis) and glycogen phosphorylase both targeted
Can be acute (dephosphorylation of phosphorylase) or long-term (suppression of PEPCK gene expression)

353
Q

Describe the effects of insulin on adipocyte lipid metabolism

A

Stim: lipoprotein lipase (LPL), FA uptake, triglyceride esterification
Inhib: adipose TAG lipolysis preventing release of FA and glycerol

354
Q

What are the functions of glucagon?

A

Stim. glycogenolysis
Stim. gluconeogenesis
Stim. lipolysis

355
Q

Describe how glucagon is regulated

A

Inc. Glc inhib. release
AAs stim. release
Stress: AD acts on B receptors on a cells stim. release
Insulin inhib. glucagon release

356
Q

How does glucagon stimulate hepatic Glc production?

A

Stim. gluconeogenesis and glycogenolysis

357
Q

Describe the effects on insulin and glucagon on hepatic lipid homeostasis during fasting

A

Insulin: suppresses lipin-1 red. VLDL production, carnitine palmitoyltransferase 1 (CPT1) thus inhib. ketogenesis

Glucagon: opposite effects thus inc. VLDL production and stim. ketogenesis

358
Q

What is the structure of glycogen?

A

Polymer of glucose residues linked a(1,4) between molecules and a(1,6) at branching points

359
Q

What does glycogen phosphorylase catalyse?

A

Gly(n residues) + Pi -> gly(n-1 residues) + glc-1P

Catalyses phosphorolytic cleavage of a(1,4) glycosidic linkages
Glc-1P released as product

360
Q

What is the prosthetic group for GP?

A 
Pyridoxal phosphate (PLP)
Phosphate used to break bond
361
Q

What is the function of phosphoglucomutase?

A

Catalyse glc-1P -> glc-6P
Glc-6P either enter glycolysis or dephosphorylated for release to blood
Free energy = 0, reaction dependent on conc.

362
Q

Explain how glycogen debranching enzyme work

A

When 4 residues left glycogen phosphorylase stops
a(1,4) transglycosylase transfers 3 residues into linear chain
a(1,6) glucosidase removes remaining glc

363
Q

Describe liver glycogenolysis and its importance

A

Glc-6Pase coverts glc-6P to glc
Liver gly converted to glc due to presence of glc-6Pase

Substitutes for gut during initial stage of starvation as liver glycogen results in direct release of glucose

364
Q

Describe skeletal muscle glycogenolysis

A

Lack glc-6Pase so glc-6P enters glycolysis
Glycogenolysis generates ATP for contraction
Lactate generated transported in blood to liver, precursor for gluconeogenesis

365
Q

What are the 2 steps of glycogen synthesis?

A

Formation of UDP-glc

Glycogen synthesis

366
Q

Describe the formation of UDP-glc

A

From glc-1P
Glc-1P + UTP -> UDP-glc + PPi
PPi + H20 -> 2Pi
Overall: Glc-1P + UTP -> UDO-glc + 2Pi

Spontaneous hydrolysis of P bond in PPi drives reaction
Cleavage of PPi only energy cost in glycogenesis

367
Q

Describe glycogen synthesis

A

Glycogen synthase catalyses
Gly(n residues) + UDP-glc -> gly(n+1 residue) + UDP

Catalyses transfer of glc to OH C4 of terminal residue of gly chain forming a(1,4)
Branching enzyme transfers segment from end of gly to OH C6 of glc residue of gly forming a(1,6) 4 residues from existing branch

368
Q

How is glycogenesis regulated?

A 
Modification 1 (phosphorylase)
Phosphorylase b (less active) phosphorylated to phosphorylase a (more active) which inhib. glycogenesis
Dephosphorylated by phosphoprotein phosphatase-1
Modification 2 (glycogen synthase)
GS a (active) phosphorylated to GS b (inactive) inhib. glycogenesis
Dephosphorylated by phosphoprotein phosphatase-1
369
Q

Explain how cAMP controls glycogenesis

A

Glucagon and NA inc. cAMP levels, activates PKA
PKA phosphorylates GS to inactive form - inhib. glycogenesis
PKA phosphorylates phosphorylase kinase (active) which phosphorylates GP (active) inhib. glycogenesis (enhance glycogenolysis)
Insulin inhib. cAMP suppressing glycogenolysis

370
Q

Describe insulin control of glycogenesis

A

Insulin activates GS phosphatase which dephosphorylates GS (active)
Glycogenesis occurs
GS kinase 3 and cAMP phosphorylate (inactive) GS, insulin suppresses GSK3, cAMP enhancing glycogenesis

371
Q

What is gluconeogenesis?

A

Synthesis of glc from non-carb C substrates - lactate, pyruvate, glycerol, glycogenic AAs

372
Q

What is the importance of gluconeogenesis?

A

During fasting liver glycogen is depleted
Gluconeogenesis is source of glucose during this
Requires energy and C source

373
Q

What are the 2 important enzymes of gluconeogenesis and where are they found?

A

Pyruvate carboxylate - mitochondria

Glc-6Pase - ER

374
Q

What is the role of pyruvate carboxylase?

A

Catalyse pyruvate to oxaloacetate

Allosterically activated by acetyl-CoA
[oxaloacetate] limiting factor for Krebs cycle
In active gluconeogenesis oxaloacetate diverted to form glc, inc. [acetyl-CoA] activates pyruvate carboxylase

375
Q

Outline the steps of gluconeogenesis

A

Opposite of glycolysis with 4 differences

  1. PC: pyruvate -> oxaloacetate
  2. PEPCK: oxaloacetate -> phosphoenolpyruvate
  3. Enolase: PEP -> 2-phosphoglycerate
  4. Phosphoglycerate mutase: 2-phosphoglycerate -> 3-phosphoglycerate
  5. Phosphoglycerate kinase: 3-phosphoglycerate -> 1,3-bisphosphoglycerate
  6. Glyceraldehyde-3P Dehydrogenase: 1,3-bisphosphoglycerate -> glyceraldehyde-3P
  7. Triosphosphate isomerase: glyceraldehyde-3P dihydroxyacetate-P
  8. Aldolase: glyceraldehyde-3P + dihydroxyacetate-P -> fructose-1,6-bisP
  9. Fructose-1,6-bisPase: fructose-1,6-bisP -> fructose-6P
  10. Phosphoglucose isomerase: fructose-6P -> glucose-6P
  11. Glc-6Pase: glucose-6P -> glucose
376
Q

How is the pyruvate kinase reaction of glycolysis reversed in gluconeogenesis?

A

Using pyruvate carboxylase, malate dehydrogenase, PEP carboxykinase

Pyruvate enters mitochondria and converted to oxaloacetate by PC
MDH catalyses oxaloacetate to malate
Malate exits mitochondria converted to oxaloacetate (enters gluconeogenesis)
Oxaloacetate converted to PEP by PEPCK and continues gluconeogenesis

377
Q

How is gluconeogenesis regulated?

A

Glc-6Pase: [Glc-6P]
Fructose-1,6-bisPase: AMP, fructose-1,6-bishop (inhib)
PC: acetyl-CoA (enhance)

378
Q

Describe the effect of glucagon-cAMP cascade in the liver

A

Gluconeogenesis stim
Glycolysis inhib
Glycogenesis inhib
Glycogenolysis stim

Free glc released to blood

379
Q

Explain how glucose/glycogen can be a C source for gluconeogenesis

A

Glycolysis forms lactate which is converted to pyruvate by lactate dehydrogenase

380
Q

Explain how proteins can be a C source for gluconeogenesis

A

Proteolysis forms AAs which are broken down to pyruvate

All AAs except lysine and leucine can supply C

381
Q

Explain how triglyceride can be a C and ATP source

A

Lipolysis produces glycerol and FAs
Glycerol enters hepatic gluconeogenesis

FAs oxidised releasing ATP, acetyl-CoA, NADH
Acetyl-CoA and NADH inhib. pyruvate dehydrogenase enzyme (prevents loss of CO2, more pyruvate for gluconeogenesis)
Acetyl-CoA enhances PC (more oxaloacetate)

382
Q

Outline the 8 steps of the TCA cycle
Can I Keep Selling Sex For Money Officer?
CAIK Sounds So Fucking Mint

A 
Citrate
Isocitrate
a-ketoglutarate
Succinyl-CoA
Succinate
Fumarate
Malate 
Oxaloacetate 
Citrate synthase
Aconitase
Isocitrate dehydrogenase
a-ketoglutarate dehydrogenase
Succinyl-CoA synthase
Succinate dehydrogenase 
Fumarase
Malate dehydrogenase
383
Q

What step of TCA is substrate level phosphorylation?

A

Succinyl-CoA synthase: Succinyl-CoA succinate

GDP -> GTP

384
Q

What are the products of TCA per glucose?

A

6 NADH2
2 FADH
2 GTP

385
Q

What 3 subunits make pyruvate dehydrogenase enzyme?

A
  1. Pyruvate carboxylase
  2. Lipoamide reductase transacetylase
  3. Dihydrolipoyl dehydrogenase
386
Q

What are the 3 conditions and fates of acetyl-CoA?

A
  1. Presence of carbs and energy used: metabolised to CO2, NADH, FADH2, GTP - all eventually ATP
  2. No energy use: made into fat
  3. Energy, no carbs: ketone bodies
387
Q

What 2 steps of TCA are endergonic?

A

Aconitase: citrate isocitrate

Malate dehydrogenase: malate oxaloacetate

388
Q

What are the 2 regulatory steps in TCA?

A

Isocitrate dehydrogenase

a-ketoglutarate dehydrogenase

389
Q

What factors stimulate and inhibit the 2 regulatory dehydrogenases?

A
  1. Inc. [ATP/NADH] inhibits

2. Ca2+ stimulates

390
Q

In the fed state what is the biosynthetic role of TCA?

A

Excess glucose converted to acetyl-CoA then citrate which is exported from mitochondria
ATP and citrate lyase convert citrate to acetyl-CoA and oxaloacetate
Acetyl-CoA then enters lipogenic acid and cholesterol synthesis pathways to forms FAs and cholesterol

391
Q

What is the biosynthetic role of TCA in the fasted state?

A

AAs that can be converted to oxaloacetate yield net glucose synthesis
FAs can’t be converted as C atoms from acetyl-CoA lost as CO2
Acetyl-CoA can’t be converted to pyruvate as reaction irreversible

392
Q

How does FA oxidation block glucose oxidation?

A

Acetyl-CoA and NADH (produced by FAO) are inhibitors of PDC which converts pyruvate to acetyl-CoA
Acetyl-CoA and NADH stimulate PDC kinase to phosphorylate PDC to inactive form

393
Q

What happens to citrate when glucose is ample?

A

Exported from mitochondria and converted to acetyl-CoA then malonyl-CoA (FA synthesis precursor)
Rise in malonyl-CoA inhibits COR-1 and suppresses FAO

394
Q

How do hypoxic events upregulate glycolysis?

A

Hypoxia-inducible factor (HIF1) transcription factor is stabilised, bind to hypoxia responsive elements in promoter regions including glycolytic enzymes

395
Q

How does chronic HIF action low mitochondrial respiration?

A

HIF1 downregulates mitochondrial respiration by promoting mitochondria autophagy and suppressing mitochondrial biogenesis
May be adaptive mechanism to prevent oxidative stress by restricting production of reactive oxygen species

396
Q

Defined glucogenic and ketogenic

A

Glucogenic: glucose can be formed from C skeleton
Ketogenic: AAs degraded to acetyl-CoA

397
Q

What are the 10 essential AAs?

PVT TIM HALL

A

Phenylalanine
Valine
Tryptophan

Threonine
Isoleucine
Methionine

Histidine
Arginine
Leucine
Lysine

398
Q

Give an overview of AA metabolism

A

Ingested protein, biosynthesis and degraded proteins produce AAs
AAs produce proteins, purines, pyrimidines, porphyrins
Degraded to C skeleton and N
N excreted in urea
C skeletons to ketogenic/glucogenic products

399
Q

What are the 3 steps to AA degradation?

A

NH2 group removed
Detoxification of amino group
Metabolism of C skeleton

400
Q

Outline the urea cycle

A

Ammonia converted to carbamoyl phosphate which reacts with ornithine to form citruline
Citruline converted to arginino-succinate by argininosuccinate synthase and broken down to arginine by argininosuccinate lyase
Arginine converted to ornithine releasing urea by arginase

401
Q

What are the general effects of insulin?

A 
Start
Glucose uptake in muscle, adipose
Glycolysis 
Glycogen synthesis 
Protein synthesis
Uptake of ions 
Stop
Gluconeogenesis
Glycogenolysis 
Lipolysis
Ketogenesis
Proteolysis
402
Q

Compare regulation of blood glucose in fed and fasting states

A

Fed: insulin secreted by beta cells, stimulates synthesis of metabolic fuel store, lower glucose level

Fasting: glucagon secrete by alpha cells, stimulates mobilisation of metabolic fuel store, raises glucose

403
Q

Describe diabetes mellitus

A

Common endocrine disorder characterised by hyperglycaemia due to defects in insulin production, an absolute or relative lack of insulin or cell resistance to insulin

404
Q

What are the 2 main types of diabetes?

A
  1. Insulin dependent DM/Type 1: IDDM

2. Non-insulin dependent DM/Type 2: NIDDM

405
Q

What is secondary diabetes mellitus?

A

Diabetes that arises as consequence of another condition

406
Q

How may secondary diabetes arise?

A

Pancreatic disease
Endocrine disease
Drug therapy
Insulin receptor abnormality

407
Q

Describe T1 diabetes

A

Can occur at any age, most common in young
Autoimmune destruction of beta cells cause absolute lack of insulin
Viral infections may be possible precipitating factor

Can be predicted by presence of Islet cell antibody presence in serum

408
Q

Describe T2 diabetes

A

Occur any age, most common 40-80yo

Resistance of tissues to action of insulin, insulin levels normal to high
Commonly associated w/ obesity

409
Q

What is type 3 diabetes?

A

Gestational diabetes

Occurs in 3-10% pregnancies

410
Q

Describe T3 diabetes

A

Non-diabetics exhibit high blood glucose during pregnancy

Presence of human placental lactogen interferes w/ susceptible insulin receptors causing them to not function properly

411
Q

What are the risks associated w/ T3 diabetes?

A

Being large for gestational age, low blood sugar, jaundice (in child)

Unmanaged: develop T2, higher incidence of pre-eclampsia, C-section

Children: obesity and T2 diabetes

412
Q

What predisposing factors are associated w/ T1 diabetes?

A

Interplay of 3 leading to selective destruction of beta cells

  1. Genetic
  2. Environmental: diet, toxins, viral
  3. Autoimmune: presence of islet antibodies
413
Q

What predisposing factors are associated w/ T2 diabetes?

A

Complex genetic interactions modified by environmental
Genetic: familia aggregation, susceptibility genes
Obesity, physical inactivity, stress
Adipocyte-derived hormones and cytokines, metabolically active hormones may affect insulin sensitivity

414
Q

What 6 symptoms are associated w/ hyperglycaemia?

A
  1. Polyuria
  2. Polydipsia
  3. Lassitude
  4. Weight loss
  5. Polyphagia
  6. Blurred vision
415
Q

What complications are associated w/ diabetes?

A

Leading cause of death and early disability
Inc. risk of cardiac, cerebral, peripheral vascular disease
Altered hand/foot sensation
Inc. risk of periodontal disease

416
Q

What are the acute compilations of diabetes?

A
  1. Hyperglycaemia
  2. Diabetic ketoacidosis
  3. Hyperglycaemic hyperosmolar non-ketotic coma
417
Q

What are 5 chronic complications of diabetes?

A
  1. Microangiopathy: small blood vessels
  2. Macroangiopathy: large blood vessels
  3. Neuropathy:
  4. Retinopathy: blindness
  5. Nephropathy: kidney failure
418
Q

What are the 3 main tests for diabetes?

A
  1. Random blood sample
  2. Fasting blood sample
  3. Oral glucose tolerance test
419
Q

For random blood glucose, at what level would diabetes be diagnosed?

A

> /= 11.1 mmol/L

420
Q

For fasting sample what levels of glucose are deemed non-diabetic, impaired fasting glycemic and diabetic?

A

Non: <6.0
Impaired: 6.1-6.9
Diabetic: >7.0

421
Q

For oral glucose test what glucose levels for fasting and 2 hours later are deemed impaired glucose tolerance and diabetic?

A

Fasting: impaired <7.0, diabetic >/=7.0

2 hour: impaired 7.8-11.0, diabetic >/=11.1

422
Q

Why is HbA1c assessment preferred in monitoring diabetes?

A

More reliable and accurate assessment of long term control as represent long term blood glucose level during lifetime of protein

423
Q

What is glycation?

A

Irreversible, enzymatic attachment of glucose to proteins

424
Q

What is HbA1c count?

A

Measurement of average blood glucose level during preceding 60-90 days before testing
Measured as % of total haemoglobin conc.

425
Q

What is a good HbA1c count?

A

7%

426
Q

What are the 4 predisposing factors of diabetic ketoacidosis?

A

All in/direct result of lack of insulin

  1. Infection
  2. Myocardial infarction
  3. Trauma
  4. Omission of insulin
427
Q

What happens in the absence of insulin?

A

Muscle and adipose breakdown triglycerides to produce FAs as alternative energy source

Inc. lipolysis leads to overproduction of FAs, converted into ketones can cause ketonaemia, metabolic acidosis, ketonuria

428
Q

What happens as glucose transport into tissues decreases?

A

Hyperglycaemia leading to glycosuria resulting in osmotic diuresis causing loss of water and electrolytes
Will result in severe dehydration, cause pre-renal uraemia and may lead to hypovolaemic shock

429
Q

What is the clinical relevance of diabetes?

A

How will treatment subsequently affect eating: will it lead to hypoglycaemia?

Collapsing
Hyperglycaemia: loss of consciousness but long process from onset of symptoms to loss of consciousness
Hypoglycaemia: may be evident within mins, rapidly lead to loss of consciousness or develop gradually and lead to profession of alteration in consciousness

430
Q

What is a counter regulatory hormone?

A

A hormone that opposes affect of another hormone i.e. an antagonist

431
Q

What are the 4 main insulin CRHs and what do they respond to?

A
  1. Glucagon
  2. AD
  3. Cortisol
  4. Growth hormone

Respond to hypoglycaemia

432
Q

What are the 3 methods for non-diabetic control of hypoglycaemia?

A
  1. Pancreas reduce insulin secretion
  2. Alpha cells secrete glucagon, liver release more glucose
  3. Adrenal glands secrete AD; liver and kidneys produce more glucose
    prevents tissues using glucose from bloodstream
    red. insulin secretion
433
Q

What happens if glucagon and AD fail to return glucose levels to normal?

A

hGH and cortisol will raise glucose

434
Q

What is the function of hGH?

A

Childhood: regulate growth rate
Adult: maintain muscle and bone mass, tissue repair and healing

Secreted by somatotrophs
Main function is to stimulation production of insulin-like growth factor by cells in liver, skeletal muscle, cartilage, bone

435
Q

What is the function of ILGF?

A

Stimulate release of glucose into blood by liver

436
Q

What do hypoglycaemia and hyperglycaemia stimulate the hypothalamus to release?

A

Hypo: GH-releasing hormone
Hyper: GH-inhibiting hormone

437
Q

What are the sections of the adrenal glands?

A

Cortex: outer 80%
Medulla: inner 20%

438
Q

Describe the adrenal cortex

A

Many LDL receptors
Enable cholesterol uptake for steroid hormone synthesis
Secrete: glucocorticoids (cortisol), mineralcorticoids (aldosterone), androgens

439
Q

Describe the adrenal medulla

A

Secrete: catecholamine hormones (NA, AD) and dopamine

440
Q

Describe cortisol

A

Secreted in response to ACTH from pituitary

-ve feedback loop

441
Q

Describe aldosterone

A

Stimulated by inc. K+ plasma

Regulates electrolyte balance

442
Q

Describe androgens

A

Steroid hormones that have masculinising effects

443
Q

What are the 3 hormone systems of the adrenal glands?

A
  1. Glucocorticoids (cortisol)
  2. Mineralcorticoids (aldosterone)
  3. Androgens
444
Q

What is adrenocorticotrophic hormone?

A

Regulatory hormone secreted by corticotrophs in ant. pituitary
Controls production and secretion of cortisol/glucocorticoids by adrenal cortex

Stimulated by CRH from hypothalamus, stress stimuli (trauma, blood glucose) and interleukin-1 from macrophages

445
Q

Describe the action of glucocorticoids/cortisol

A

Binds to cytosolic receptor and translocated to nucleus upon activation
Regulates BP and suppresses inflammation

Enhances: gluconeogenesis, adipose tissue lipolysis, muscle proteolysis
Inhib: glucose utilisation

446
Q

Describe catecholamine action

A

Release in response to stress
Characterised by inc. O2 consumption and hypermetabolism

AD stim: glycogenolysis in liver and muscle; gluconeogenesis in liver
Stim: adipose alternative fuel cells to glucose
Inc. HR

447
Q

Describe hypofunction of the adrenal glands

A

Adrenal insufficiency; rare, potentially fatal
Signs: lethargy, anorexia, low BP, hypoglycaemia, hyperpigmentation
Life threatening Na depletion and possible K retention due to aldosterone deficiency causing low BP
Therapy: Na maintenance, hormone replacement

448
Q

What is hyperfunction of adrenal cortex?

A

Overproduction of cortisol, androgens and aldosterone

Prolonged, excessive exposure can lead to Cushing’s syndrome

449
Q

What is Cushing’s syndrome?

A

When ACTH levels don’t respond to -ve feedback from high cortisol levels

Characterised by remodelling of adipose tissue: deposition on face and trunk, loss from limbs
Wasting of skeletal muscle, osteoporosis, slow healing, thinning of skin
Excess cortisol may lead to diabetes and hypertension

450
Q

What are tetraiodothryonine and triiodothyronine?

A

Thyroid hormones 4 and 3
Are thryonines w/ 3/4 iodine atoms

Regulated by controlling conversion of 4 to 3 (active from) in target tissues (liver, kidney)

451
Q

Described the mechanism of thyrothropin releasing hormone and thyroid stimulating hormone

A

TRH controls TSH release
TSH stimulates production and secretion of T3 and 4 by thyroid
T3and4 control release of TRH

452
Q

What are the 9 general metabolic effects of thyroid hormones?

A

Inc: basal metabolic rate, body temp, glucose and FA use for ATP synthesis, glucose uptake, lipid and protein turnover

Stim: protein synthesis, lipolysis, synthesis of Na/K ATPase

Effect on gene expression: slow, long lasting

Regulate development and growth of nervous tissue and bones

453
Q

What are the 8 clinical features of hypothyroidism (myxoedema)?

A
  1. Lethargy, tiredness
  2. Weight gain
  3. Apathy
  4. Slow pulse
  5. Cold intolerance
  6. Constipation
  7. Myxoedema
  8. Elevated serum TSH
454
Q

What are the 7 clinical features of hyperthyroidism (thyrotoxicosis)?

A
  1. Hyperactivity, insomnia
  2. Weight gain
  3. Diarrhoea
  4. Palpitation
  5. Heat intolerance
  6. Suppressed TSH, elevated T4
  7. Agitation
455
Q

What is body mass index?

A

Universally accepted classification of obesity

Person’s weight (kg) in relation to height (m)

456
Q

What are the BMIs for normal, over weight and the 3 classes of obesity?

A 
Normal: 18.5-24.9
Overweight: 25.0-29.9
Class I: 30.0-34.9
Class II: 35.0-39.9
Class III: >40.0
457
Q

Describe the co-morbidity risk changes as weight inc.

A 
Normal: no inc.
Overweight: inc.
Class I: moderate inc.
Class II: severe inc.
Class III: v severe inc.
458
Q

Discuss the advantages of BMI

A

Low-cost, easy to use
Commonly used to determine healthy weight, can compare weight to GP
Correlates well w/ amount body fat measured by complex techniques
Predicts dangers; as BMI inc. risk inc.
Useful screening tool to use @ popn. level, as universally used lots of data from many popns.

459
Q

What is the disadvantage of BMI?

A

Fails to distinguish between fat and muscle

460
Q

What is obesity?

A

Excessive accumulation of fat

461
Q

What 2 methods can be used to assess obesity?

A
  1. Waist circumference

2. Waist-hip ratio

462
Q

Describe waist circumference

A

Taken at level of iliac crest
Men: >40” health risk
Women: >35” health risk

463
Q

Describe waist-hip ratio

A

Waist circumference @ level of L3 over hip circumference @ largest gluteal region

Men: >1.0
Women: >0.85

464
Q

Describe the changes in epidemiology and prevalence of obesity

A

WHO says it is now an epidemic

In last 10yrs inc. by 10-40% in most European countries

465
Q

Describe prevalence of obesity in Britain

A

Now has highest obesity rate of all Western European counties: 50% overweight, 20% obese

> 1.1billion adults overweight, 312mil clinically obese
10% children overweight/obese, 17.6mil <5 overweight

466
Q

What are the 4 main factors for cause of obesity?

A
  1. Genes
  2. Socio-economic: diet and lifestyle
  3. Cultural
  4. Psychological and medical
467
Q

What is the evidence for genes playing a role in obesity?

A

Adults who were adopted as children have weight closer to biological parents

Monozygotic twins show much stronger correlation in weight than dizygotic twins

468
Q

Describe the socio-economic factors in obesity

A

Diet
Inc. energy dense foods: animal fats
Dec. complex carbs: fibres, coarse grains
Inc. alcohol, salt

Lifestyle
Affluent life w/ less physical activity 
Car: drive instead of walk
TV/games: long time sitting/watching
Energy/time saving devices: red. manual labour in home
469
Q

How do cultural factors play a role in obesity?

A

In some countries big is attractive and sign of health and prosperity

470
Q

Describe the psychological and medical factors contributing obesity

A

Psychological: eat in response to -ve emotions; sadness, anger, boredom

Conditions: depression, hypothyroidism, chromosomal anomalies

Drugs: corticosteroids, antidepressants, antipsychotics, B-blockers, oral contraceptive, oral hypoglycaemic agents, insulin, antihistamines

471
Q

What are the 9 possible effects of obesity?

A
  1. Hypertension
  2. Stroke
  3. T2 diabetes
  4. Cancer: endometrium, breast, prostate, colon
  5. CV mortality
  6. Respiratory diseases, sleep-apnea
  7. Osteoarthritis
  8. Gallbladder disease
  9. Metabolic syndrome
472
Q

What are the 2 main types of obesity?

A
  1. Intra-abdominal/visceral

2. Lower body/external

473
Q

What are the 6 main CV diseases associated with obesity?

A
  1. Hypertension
  2. Atherosclerosis
  3. L ventricle hypertrophy
  4. Cardiac necrosis
  5. Cardiac arrhythmias
  6. Heart attack
474
Q

How does obesity cause hypertension?

A

Inc. body mass associated w/:
Inc. blood vol. and viscosity
Inc. angiotensinogen release from adipocytes
Inc. cholesterol and BP

475
Q

What effect does atherosclerosis have on the heart?

A

Inc. workload

476
Q

What affect does inc. workload have on the heart?

A

L ventricle hypertrophy

477
Q

What happens when heart workload continues to inc.?

A

Coronary arteries unable to sustain heart
Ischaemia: lack of blood
Unable to manifest during high demand

Heart loses elasticity: unable to relax completely, dec. filling, dec. blood pumped around body

478
Q

What is congestive heart failure?

A

Inability of heart to contract properly

479
Q

Explain how obesity can lead to T2 diabetes

A

Insulin secreted in response to intake of food
Prolonged periods of food intake causes constant production of insulin
Cellular insulin receptors are down regulated leading to insulin resistance
High levels of FAs and glucose in blood
Depletion of glucose reserves as glucose not transported
Person feels hungry and eats more

480
Q

What are the 5 methods of treatment of obesity?

A
  1. Dietary modifications
  2. Behavioural modifications
  3. Physical activity
  4. Pharmacological
  5. Surgery
481
Q

Describe dietary modifications for the treatment of obesity

A

Nutritionally balanced, low calorie

Inc.: fruit, veg, whole grains, nuts
Dec.: fatty, sugary foods

482
Q

Describe some behavioural modifications to treat obesity

A

Keep food diary: time, place, activity, emotions; find link to period of eating/inactivity

Help to avoid eating when in feet, watching TV, playing games etc

Encouraged to eat home cooked meals and walk rather than use car

483
Q

When should pharmacological treatment of obesity be considered?

A

18-75yrs: BMI >30
BMI >27 w/ pre-existing risk factor: hypertension, diabetes, obstructive sleep apnoea, cardiac disease
BMI >30 and 3 months care not red. weight

484
Q

What 2 drugs are licensed to be used in treatment of obesity?

A
  1. Orlistat

2. Sibutramine

485
Q

Describe orlistat

A

Prevents fat digestion and absorption by binding to GI lipase
Useful for those w/ high fat diet

486
Q

Describe sibutramine

A

Red. appetite and inc. thermogenesis

Useful for those who can’t control appetite

487
Q

What must be taken into consideration when a patient is on pharmacological treatments of obesity?

A

Shouldn’t be sole therapy
Must be strictly and regularly monitored: discontinued if weight loss <5% after 12ws or weight gain recurs
Shouldn’t be on longer than year, never more than 2 years

488
Q

Describe surgical treatment of obesity

A

Only in severe cases: BMI >40

2 accepted procedures: gastroplasty, gastric bypass
Both red. stomach to small pouch to limit amount of food that can be consumed

489
Q

Describe vitamins

A

Class of organic compounds categorised as essential nutrient

Required for normal function, growth and maintenance
Essential for several enzymatic process in human metabolism
Are cofactors: don’t do anything themselves

490
Q

What are the 2 classes of vitamins?

A
  1. Fat soluble: A D E K

2. Water soluble: B complexes, C

491
Q

Describe water soluble vitamins

A 
Source: fruits, vegs, grains, meat
Absorption: directly into bloodstream 
Storage: circulating freely, not stored in body
Excretion: excess in urine
Toxicity: rare, possible w/ supplements
492
Q

Describe fat soluble vitamins

A 
Source: fats and oils in food
Absorption: w/ lipids through lymphatic system
Storage: in fat and liver
Excretion: not easily excreted
Toxicity: easily reached
493
Q

Describe the sources, RDA and toxicity of vit A

A

Source: meat, liver, diary products Retinol - active form
yellow, red, green fruits and vegetables; Carotene - precursor

RDA
men: 0.7mg/day; women: 0.6mg/day

Toxicity: >1.5mg/day
Painful joint, anorexia and/or vomiting, liver damage, fatigue, loss of hair

494
Q

What are the 4 functions of vit A?

A
  1. Promote vision: retinal needed in rhodopsin
  2. Protein synthesis and cell differentiation
  3. Reproduction and growth
  4. Bone growth remodelling
495
Q

What are the 5 ocular and 3 extra-ocular effects of vit A deficiency?

A

Ocular

  1. Night blindness
  2. Conjunctival xerosis
  3. Bitot’s spots
  4. Corneal xerosis
  5. Keratomalacia

Extra-ocular

  1. Retarded growth
  2. Skin disorders
  3. Effect on bone
496
Q

Describe Bitot’s spots, conjunctival xerosis and keratomalacia

A

Bitot’s spots: foamy whitish cheese-like tissue spots, cause severe dryness

Conjunctival xerosis: conjunctiva becomes dry and non-wettable, appears muddy and wrinkled

Keratomalacia: cornea becomes soft, may burst open, if eye collapses vision lost

497
Q

What is carotenemia?

A

Impairment of conversion of carotene to Vit A due to inborn metabolic error or hepatic disease
Generalised yellowish skin and mucosa
Excessive deposition of carotene due to high intake of carotene containing foods

498
Q

What are the 5 oral manifestations of vit A?

A
  1. Xerostomia
  2. Altered taste
  3. Gingival hypertrophy
  4. Dec. ameloblast and odontoblast formation
  5. Disrupted enamel formation, irregular tubular dentine formation
499
Q

What is unique about Vit d?

A

Only fat soluble vitamin humans can synthesise

500
Q

What are vit D3 and D2?

A

D3: cholecalciferol
D2: ergosterol

501
Q

Describe the metabolic synthesis of vit D3

A

Cholesterol converted to 7-dehydrocholesterol
UV rays convert 7DC to cholecalciferol which is then hydrolysed in kidney and liver to active 1,25-dihydroxycholecalciferol

502
Q

What are the dietary sources of vit D3?

A 
Cheese
Butter
Margarine
Fish
Fortified milk and cereals
503
Q

What are the RDAs for vit D?

A

Pregnant/breastfeeding/>65: 0.01mg/d

6m-5y: 0.007-0.0085mg/d

504
Q

What are the 7 signs and 2 complications of vit D toxicity?

A
  1. Constipation
  2. Anorexia
  3. Fatigue
  4. Muscle weakness
  5. Irritability
  6. Vomiting
  7. Dehydration

Complications

  1. Kidney stones
  2. Kidney failure
505
Q

What are the 5 functions of vit D?

A
  1. Ca and K balance
  2. Bone and tooth development: enhance Ca absorption in gut and renal tubules
  3. BP regulation
  4. Immunity
  5. Cell differentiation
506
Q

What are the affects of vit D deficiency?

A

Rickets: dec. Ca, poor calcification, deformed bones
Osteomalacia: post-menopause, bone pain, weak muscle
Inc. risk of osteoporosis

507
Q

What are the 4 oral manifestations of vit D deficiency?

A
  1. Teeth: developmental abnormalities in enamel and dentine
  2. Higher risk of caries
  3. Enamel hypoplasia
  4. Pulp: high horns, large chamber, delayed closure of root apices
508
Q

What are the 2 types of vitK and their sources?

A

K1: plant; spinach, cabbage, broccoli, cauliflower, wheat germ, tomatoes, potatoes, carrots

K2: synthesised by intestinal bacteria from milk, fish, meat

509
Q

What is the RDA for vitK?

A

0.001 mg/d per kg weight

510
Q

What are the 2 functions of vitK?

A
  1. Production of blood clotting factors II, V, VII, IX, X

2. Bone mineralisation: VitK-dependent proteins; osteocalcin, matrix Gla protein, protein S role in matrix formation

511
Q

What are the effects of vitK deficiency?

A

Inc. prothrombin time and risk of haemorrhage

Bone deformation

512
Q

What is the oral manifestation of vitK deficiency?

A

Uncontrollable gingival/mucosal bleeding

513
Q

What is VitE? Generally describe function and how it works

A

Family of 8 naturally occurring compounds
Powerful antioxidant, present in anti ageing products
Intercepts free radicals, prevents destruction of cell membrane

514
Q

What are the sources of VitE?

A

Egg, fish, liver, butter

Soybean, palm oil, sunflower, corn, olive, nuts, green leafy veg, whole grain

515
Q

What is the RDA for vitE?

A

Men: 4mg/d
Women: 3mg/d

516
Q

What is the function of vitE?

A

Promote vasodilation
Inhibit platelet aggregation
Prevent atherosclerosis by preventing oxidation of LDLs

517
Q

What are the effects of a VitE deficiency?

A

Premature ageing: hair, nails, skin
Inc. risk of CVD
Degenerative changes in blood capillaries

518
Q

Name the B complex vitamins

A 
B1: thiamin 
B2: riboflavin
B3: niacin 
B5: pantothenic acid
B6: pyridoxamine
B12: cobalamin 
Biotin
Folic acid
519
Q

What are the sources of vitBs?

A

Yeast, grain, rice, fish, veg, meat

520
Q

What is the effect of toxicity of B6?

A

> 5.0mg/d
Nerve damage, difficulty walking
Numbness in feet and hands

521
Q

What are the 4 functions of vit Bs?

A
  1. Co-enzymes
  2. Energy metabolism: B1-6 and biotin
  3. RBC synthesis: folate, B12
  4. Homocysteine metabolism: folate, B6 and 12
522
Q

What is the effect of B1 deficiency?

A

Beriberi: after 10 days

Weakness, nerve degeneration, irritability, poor leg/arm coordination, loss of nerve transmission
Oedema, enlarged heart, heart failure
Due to poor glucose metabolism

523
Q

What is the effect of B2 deficiency?

A

Ariboflavinosis: occurs within 2 months

Glossitis, cheilosis, stomatitis, nervous system disorder

524
Q

What does B3 deficiency cause?

A

Pellagra

Scaly sores, mucosal changes and mental syndrome

525
Q

What does B6 deficiency result in?

A 
Depression
Nerve irritation
Skin disorders
Vomiting
Impaired immune system
526
Q

What does B12 deficiency cause?

A

Megaloblastic anaemia

Large and irregular RBCs

527
Q

What oral manifestations do vit B deficiencies result in?

A

B2: glossitis, stomatitis, cheilosis
B12: aphthous ulcer

528
Q

What are the sources of vitC in humans?

A

Citric fruits

529
Q

What is the RDA for vit C?

A

40 mg/d

530
Q

What 3 things does toxicity of vit C result in?

A

> 1000 mg/d

  1. Stomach pains
  2. Diarrhoea
  3. Flatulence
531
Q

What are the 5 functions of vit C?

A
  1. Antioxidant
  2. Enhance iron absorption
  3. Synthesis of collagen
  4. Immune: reduce cold duration by 1 day
  5. Wound healing
532
Q

What does vit C deficiency cause?

A

Scurvy: 20-40 day deficient

Fatigue, pinpoint haemorrhages
Bleeding gums and joints

533
Q

What are the oral manifestations of vit C deficiency?

A

Loosening of teeth and tooth loss

Gum bleeding, gingivitis

534
Q

What are the 3 most important trance minerals?

A
  1. Iodine: thyroid function
  2. Iron: haemoglobin
  3. Fluoride: bone and teeth
535
Q

What are the 2 most important major minerals?

A
  1. Phosphorus: DNA

2. Calcium: bones

536
Q

What are the 5 sources of fluoride?

A
  1. Toothpaste
  2. Fluoridated water
  3. Mouthwash
  4. Food processed w/ fluoridated water
  5. Fluoride supplements
537
Q

What is the function of fluoride?

A

Anti-cariogenic:
prevent bacterial adhesion
suppress cariogenic bacteria
change enamel crystalline structure

538
Q

Describe the changes in enamel crystalline structure due to fluoride

A

HA -> FA

Larger crystals
Higher pKa to dissolve

539
Q

What is the result of fluoride toxicity?

A

Fluorosis

Chronic
Mottled enamel w/ scattered, irregular white flecks

540
Q

Define inherited metabolic disorder

A

Metabolism disorder caused by mutation in gene that codes for enzyme resulting in enzyme deficiency and breakdown of metabolic pathway

541
Q

What are the 6 clinical presentations in neonates of IEMs and 5 in young children?

A
  1. Vomiting
  2. Seizures
  3. Irritability
  4. Poor feeding
  5. Breathing disorder
  6. Abnormal tone
  7. Recurring vomiting
  8. Dysmorphic features: characteristic facial expression
  9. Mental retardation
  10. Seizures
  11. Developmental delay: milestones
542
Q

What are the 7 categories of IEMs?

A
  1. AA metabolism disorders
  2. Carbohydrate metabolism disorders
  3. FAO disorders
  4. Lysosomal storage disorders
  5. Peroxisomal disorders
  6. Urea cycle disorders
  7. Mitochondrial disorders
543
Q

What is Von Gierke’s disease?

A

IEM characterised by deficiency of glucose-6-phosphatase
Renders glycogen stores of body inaccessible
Lack free glucose
Glucose synthesis from glucose-6-phosphate via gluconeogenesis hampered

544
Q

What are the affects of Von Gierke’s disease?

A
  1. Hypoglycaemia
  2. Lactic acidosis
  3. Hepatomegaly
545
Q

Describe galactosaemia

A

Deficiency of galactose-1P uridyltransferase

Converts galactose-1P to glucose-1P which is subsequently converted to 6P and enters glycolysis

546
Q

What are the effects of galactosaemia?

A

Child unable to utilise galactose component of lactose in milk
Accumulation of galactose-1P in blood, diarrhoea, vomiting, mental retardation, develop cataracts

547
Q

What is the result of a deficiency of liver fructokinase or fructose-1P aldolase?

A

Fructokinase: convert fructose to fructose-1P
Fructose-1P aldolase: fructose-1P to glyceraldehyde

Fructose intolerance
Results in an accumulation of fructose-1P which inhibits both glycogenolysis and gluconeogenesis leading to hypoglycaemia

548
Q

What are 2 AA metabolism disorders?

A

Alkaptonuria: black urine

Maple syrup urine disease

549
Q

Describe alkaptonuria

A

Defect in breakdown of tyrosine and phenylalanine
Causes accumulation of homogentisic acid which is excreted in urine and oxidises on standing giving urine black colour

This can lead to arthritis due to build up in cartilage

550
Q

Describe maple syrup urine disease

A

Defect in branched AA metabolism causing accumulation of keto-acids in urine

If left unmanaged can lead to physical and mental retardation

551
Q

Describe phenylketonuria

A

Defect in phenylalanine hydroxylase causes impaired conversion of phenylalanine to tyrosine

Phenylalanine accumulates in blood and excreted in urine (aminoaciduria)

552
Q

What are the signs of phenylketonuria?

A

Irritability
Vomiting
Mental retardation
Red. melanin formation

553
Q

What are the 6 presentations of phenylketonuria?

A
  1. Mental retardation
  2. Hypopigmentation
  3. Developmental delay
  4. Musty odour
  5. Autism
  6. Epilepsy
554
Q

What is familial hypercholesterolaemia?

A

Disorder caused by red. number functional LDL receptors in liver

555
Q

What are the 3 effects of hypercholesterolaemia and treatment options?

A
  1. Premature coronary heart disease
  2. Tendon xanthomas
  3. Severe hypercholesterolaemia

Modify diet, fibrates, statins, bile acid binding resins

BDS 1 (11 decks)

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