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Phase 1 Notes > IMMS - Biochemistry > Flashcards

IMMS - Biochemistry Flashcards

1
Q

Describe the different molecules present on membrane

A

Phospholipid
Cholesterol
Intrinsic / Extrinsic proteins
Carbohydrates
Glycoproteins
Glycolipids

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2
Q

Describe aspects of channel proteins

A

Passive (leaky)
May be gated
Selective (size/ charge )
Usually ions or water
Integral

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3
Q

Describe aspects of carrier proteins

A

Specific binding site undergoes conformational change. Different types:
- Uniport = single substance
- Symport = two substances in the same direction
- Antiport - two substances in opposite directions
Can be active or passive

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4
Q

3 Driving forces of substances in/out of cells

A

-Chemical
-Electrical
-Electrochemical (both)

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5
Q

Describe the driving force - chemical

A

Forces directly proportional to the concentration gradient

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6
Q

Describe the driving force - electrical

A

(Also known as membrane potential)
Force depends on size of membrane potential and charge of ion

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7
Q

Describe the driving force - electrochemical

A

Net direction is equal to the sum of chemical and electrical forces
(Only charged substances e.g. K+)

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8
Q

Types of membrane transport

A

Passive
-Simple diffusion
-Facilitated diffusion (mediated by proteins) e.g. GLUT4 uptakes glucose regulated by insulin
Active
-Primary (directly uses source of energy ATP) e.g. 3Na+/2K+ATPase
-Secondary (uses energy from transport of an ion e.g. Na+/glucose)

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9
Q

What happens when GLUT4 carrier (in pregnancy) goes wrong?

A

GLUT4 carriers in skeletal muscle and adipose tissue.
Glucose is principal foetal nutrient and levels are directly related to mothers. (Foetal gluconeogenic enzymes are inactivated)
However no mechanism to limit uptake so excess glucose can cause foetal harm.

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10
Q

What happens when GLUT1 carriers (in the brain) goes wrong?

A

GLUT1 deficiency disorder caused by mutation in gene that encodes for less functional GLUT1. This reduces amount of glucose available for brain and can cause seizures etc.

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11
Q

What happens when there is a mutation in the ATP7B gene?

A

Wilson’s disease:
Cu2+ATPase in the liver transports copper into the bile and disorder results in deposition of copper in liver and other tissues (Rings in the eyes)

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12
Q

What is the function of SGLT1 carriers?

A

Transports glucose and galactose from the intestinal lumen.
If mutation reduces functionality, malabsorption may lead to chronic diarrhoea, dehydration etc.

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13
Q

Describe communication between cells (cellular signalling)

A

Signalling molecules bind to receptors:
-Intracellular e.g. steroid hormones
-Cell surface e.g. peptide hormones
Secondary messengers e.g. cAMP, Ca2+
= Affects gene expression in the nucleus

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14
Q

Give 4 types of cellular signalling receptors

A
  • Ligand gated ion channels
  • G protein coupled receptors
  • Enzyme linked receptors
  • Intracellular receptors
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15
Q

What happens when Gprotein coupled receptors goes wrong?

A

Cholera bacteria produce toxins that modify Gas subunits permanently and results in increased secondary cAMP levels. This results in massive secretion of ions and water into the gut = fatal dehydration and diarrhoea.

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16
Q

Give some examples of endocytosis and exocytosis

A

Endo:
Phagocytosis
Pinocytosis (smaller molecules)
Receptor mediated (more accessible)
Exo:
Insulin receptor
Synaptic cleft (triggered)

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17
Q

Describe cystic fibrosis

A

Mutation in CFTR protein (chloride channel) leads to abnormal sticky, viscous mucus and disallows osmotic drag

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18
Q

Give examples of drugs that target membrane transporters

A

Cardiac glycosides e.g. digoxin (Increases Ca2+)
Proton pump inhibitors e.g. omeprazole (Inhibits parietal cels)
Loop dietetics e.g. furosemide (On loop of Henle)
Thiazide dieuretics e.g. bendroflumethiazide (On distal tube to keep water in)

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19
Q

2 Functions of cell membrane

A

Cell polarisation/ compartmentalisation
Ionic gradient (membrane potential activates functions)

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20
Q

Describe K+ homeostasis failure in kidneys

A

High K+ conc = hyperkalaemia
(Em more positive so depolarises easier = bradycardia)
Low K+ conc = Hypokalaemia
(Em more negative = arrhythmia)

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21
Q

Definition of diffusion potential

A

Electrical force requires to cross a membrane to counterbalance chemical diffusion forces of a given ion.

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22
Q

Describe ischaemia

A

Hypoxia: ATP conc decreases so opens K+ channels and resting Em ~55mv. Depolarises easily
Slow Ca2+: early Repolarisation so shorter action potential

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23
Q

Name 5 different receptors

A
  1. Ion channels (target of most drugs)
  2. Membrane bound steroid receptors
  3. Neurotransmitters
  4. Growth factors
  5. Nuclear steroid receptors
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24
Q

Describe what 4 factors affect membranes

A
  1. pH = denatures
  2. Temperature = speed of activity
  3. Regulation of SAN action potential = ions lead to Brady/tachycardia
  4. Extra cellular ion concentration:
    - Acidosis = Less Ca2+ bound to plasma proteins
    - Alkalosis = more Ca2+ bound to plasma proteins
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25
Q

Describe GPCRs

A

3 G-proteins (a,B,y) that are attached to enzymes which modulate secondary messengers (cAMP) and terminate signals.

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26
Q

Define homeostasis

A

Maintenance of a constant internal environment

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27
Q

Describe the 2 different communication systems

A
  1. Endocrine - Hormones
  2. Nervous - Electrical
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28
Q

Describe the 3 different categories of communication

A

Autocrine - cells to themselves
Paracrine - To neighbouring cells (diffuses across gaps locally e.g. PDGF released by platelets)
Endocrine - Hormones travel in blood (Organ = Thyroid, pituitary, ovaries, pancreas etc)

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29
Q

What is a hormone?

A

Molecule that acts as a chemical messenger

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30
Q

Describe the 3 different types of hormones

A

Amino acid derivative - synthesised from tyrosine e.g. adrenaline
Peptide- made from amino acids, glycoproteins and is hydrophilic
Steroids- made from cholesterol and is hydrophobic

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31
Q

Which hormones produce a quick reaction?

A

Peptide and amino acid derivatives
- Are small and are pre made then stored in cell
- Dissolves in blood and binds to receptor on target cell

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32
Q

Which hormones produce a slow reaction?

A

Steroid hormones (years)
- Diffuses out once made and transported in blood via bound protein
- Receptor is inside target cell and directly affects DNA

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33
Q

Difference between positive and negative feedback

A

Positive- signal is amplified
Negative- Maintaining a steady state

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34
Q

What is freely permeable through the phospholipid membrane?

A

Gases
Small uncharged polar
Water

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35
Q

Describe structure of water

A

Polar as O is more electronegative
Hydrogen bonding so universal solvent
Maximum density at 4degrees so ice floats

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36
Q

Name some monosaccharides

A

Carbonyl, ketones, hydroxyl, aldehyde

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37
Q

How much ingested glucose does the brain use?

A

20% (If glucose less than 3 = hypogleicimic)

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38
Q

What are glycosidic bonds formed between?

A

2 monosaccharides = disaccharide
3-12 monosaccharides = ogliosaccharide
More = polysaccharides e.g. starch, glycogen

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39
Q

Describe lipid structure

A

Straight carbon chains with carboxyl head group
More unsaturated = m.p. Decreases
Most stored and transported as triglycerides

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40
Q

Describe nucleotide structure

A

Nitrogenous base + sugar + phosphate

41
Q

Describe amino acid structure

A

Amino, carboxyl and 20 different R groups
R determines polarity
In condensation reaction, loses water to form peptide bond

42
Q

Describe protein structure

A

Primary - Peptide bonds between amino acids
Secondary - H bonds fold chain into a-helix or B-pleated sheets
Tertiary - H, ionic, disulphide, hydrophobic folds further
Quaternary - More than 1 polypeptide

43
Q

B-pleated sheets vs a-helix

A

B - H bonds between linear regions
a - H bonds between carbonyl groups

44
Q

Describe the 5 different bonds

A

Hydrogen - between dipoles of H + O/N/F
Van dear Waal - weak electrostatic attraction due to fluctuations of electron density
Ionic - Between fully or partially charged groups
Disulphide + covalent bonds between S-S of cytosine
Hydrophobic - Uncharged, non-polar side chains are hydrophobic

45
Q

What are enzymes?

A

Biological catalysts that bind substances and alter bonds so there is a lower activation energy to form products. May also stabilise reaction intermediates to speed up reactions

46
Q

Describe haemoglobin structure

A

Porphyria’s ring hold onto iron atom (heme) and is site of oxygen binding

47
Q

3 factors influencing haemoglobin saturation

A

Temperature
pH (H+ binds to Hb instead and O2 released)
pCO2
(Modifies structure of haemoglobin to decrease O2 affinity and unload)

48
Q

What is sickle cell anaemia?

A

Mutation in haemoglobin forms hard, sticky, sickle shaped red blood cells

49
Q

What are immunoglobulins?

A

Antibodies produced to bind to antigens on microbial agents

50
Q

DNA in prokaryotes vs eukaryotes

A

P - No nuclear membrane, DNA in single circular chromosome, super coiled
E - DNA bound to proteins in nucleus. Chromatin condensed to chromosomes

51
Q

Cell cycle is influenced by

A

Only starts if there is enough energy
Oncogenes
Proto-oncogenes
Cell cycle repair
DNA repair

52
Q

Describe semi- conservative DNA replication

A

DNA helicase opens up DNA
SSB proteins keep trands open and Topoisomerase unwinds it
DNA Polymerase forms new DNA behind the fork

53
Q

How are DNA damaged?

A

UV
IR
Ingesting benzene

54
Q

Name some DNA repair mechanisms

A

Tumour suppress genes
Apoptosis
Pause cell cycle

55
Q

Describe protein formation

A

Double stranded DNA transcripted
Single stranded mRNA spliced to remove introns
rRNA combines with proteins to from ribosomes
tRNA carries amino acids in translation

56
Q

What are transcription factors?

A

Control whether gene is turned off or only binding to specific exon and weakening helix

57
Q

Factors that turn off expression

A

Methylation of cysteine
Less acetylation of his tones
Reverse transcriptase and retroviruses
Activation of repressors

58
Q

What do growth hormones do?

A

Bind to and activates kinase
= phosphorylase’s a transcription factor
= transcription occurs

59
Q

Anabolic vs Catabolic

A

A - Synthesises larger molecules from smaller
C - Breaks down large molecules to smaller

60
Q

4 ways dietary components are metabolised

A

Bio synthetic (A)
Fuel storage (A)
Oxidative processes (C)
Waste disposal

61
Q

Where is energy stored?

A

Adipose tissue - 85% fat, energy rich molecules e.g. triglycerides
Liver - glycogen, water
Muscle - kinetic energy, glycogen, protein

62
Q

3 main dietary fuels

A

Carbohydrates e.g. glucose, fructose …
Lipids (1 glycerol esterified to 3 saturated fatty acids)
Proteins

63
Q

Energy per gram for 3 main dietary fuels

A

Carbohydrate - 4Kcal/g (sustains 12 hours)
Protein - 4Kcal/g (when muscle glycogen stores fail)
Alcohol - 7Kcal/g
Lipid - 9Kcal/g (up to 12 weeks)

64
Q

Define Basal Metabolic Rate (BMR)

A

Energy needed to stay alive at rest
E.g. respiration, ion gradients, repairing, contraction of heart muscle, biosynthesis

65
Q

Conditions to measure BMR

A

12 hour fast, 27-29degrees environment, no tea/coffee/nicotine for 12 hours, lying still.
(If not met = RMR Resting Metabolic Rate)

66
Q

Factors affecting BMR

A

Age
Gender
Dieting / starvation
BMI
Decreased muscle mass
Hyperthyroidism
Fever

67
Q

Body Mass Index vs Basal Metabolic Rate

A

BMI (kg/m2) - released to height and weight
BMR (kcal/kg/hour) - amount of calories for essential function

68
Q

What is the recommended kcal/kg/day?

A

23-35

69
Q

Define malnutrition

A

A state of deficient nutrient, energy or others causing measurable adverse affects

70
Q

What is refeeding syndrome?

A

Too many carbs too quickly = lots of insulin = deficiency of enzymes

71
Q

What happens in an overnight fast?

A

Glycogenolysis, insulin decreases

72
Q

What happens in 2-4 day fast?

A

Insulin and cortisol decrease
Lipolysis, preoteolysis, gluconeogenesis

73
Q

What happens in more than 4 day starvation

A

Liver produces ketones from fatty acids
Brain adapts to using ketones

74
Q

Describe adenosine triphosphate (ATP) structure

A

Adenine (purine) base, ribose sugar, 3 phosphate

75
Q

What does ATP form to release energy?

A

ADP + Pi
Last 2 phosphate groups repel each other and is easily hydrolysed to release lots of energy

76
Q

How are proteins, carbohydrates and fats metabolised?

A

Proteins -> amino acids
Carbohydrates -> glucose -> glycolysis
Glycerol -> fatty acids

-> Acetyl coA -> Krebs cycle/citric acid/TCA cycle -> Oxidative Phosphorylation

77
Q

Describe the preparation phase of glycolysis

A

Glucose enters cytosol via GLUT-1 transporters
Glucose - (ATP->ADP) -> Glucose-6-phosphate
Phosphorylation catalysed by hexokinase

-> Fructose-6-phosphate (catalysed by phosphoglucoisomerase)
- (ATP->ADP) -> Fructose-1,6-biphosphate (catalysed by phosphofructokinase)

Splits into (catalysed by aldolase):
Dihydroxyacetone phosphate (isomerise catalyses->)
Glyceraldehyde-3-phosphate ———>

78
Q

Describe the ATP generating phase of glycolysis

A

G-3-P is oxidised to 1,3-biphosphoglycerate
(2NAD+ reduced to 2NADH +2H+ Catalysed by triose phosphate dehydrogenase)

1,3-BPG - (2ADP -> 2ATP) -> 3-phosphoglycerate
(Catalysed by phosphoglycerokinase)

Phosphoglyceromutase catalyses 3-PG to 2-PG

Enolase catalyses to phosphoenolpyruvate (+2H2O)

Pyruvate Kinase catalyses to pyruvate (2ADP->2ATP)

79
Q

Why is glycolysis important?

A

Vital for emergency energy with limited O2:
.RBC don’t have mitochondria
.Muscle have fast energy demands
.Glycerol-3-P is backbone for triglycerides
.Pyruvate transaminated to alanine/substrate for fatty acid synthesis
.G-6-P for glycogen synthesis/nucleotides

80
Q

Summarise the glycolysis step

A

In cytosol, anaerobic breakdown of 1 glucose to 2 pyruvate, 2NADH and net 2 ATP

81
Q

Describe regulation of glycolysis

A

Hormones (insulin + glucagon) indirectly increases/decreases gene expression through regulatory molecules.
At 3 kinase reactions (hexokinase, pyruvate kinase, PFK-1) binds to non-catalytic site and conformational change increases/decreases substrate affinity

82
Q

What is the primary regulatory site of glycolysis?

A

PFK-1

83
Q

Activators and inhibitors of glycolysis

A

A - ADP is converted to AMP when accumulated which activates PFK1 to generate ATP
I - ATP and citrate from Krebs cycle inhibits PFK1
I - Fructose-2,6-biphosphate inhibits PFK1

84
Q

Describe link reaction (aerobic conditions)

A

Pyruvate enters mitochondria and is decarboxylate oxidated to Acetyl-CoA, NADH and CO2 by pyruvate dehydrogenase

85
Q

Describe link reaction (anaerobic conditions)

A

Each pyruvate forms lactate, 2H2O and 2ATP catalysed by lactate dehydrogenase and energy regenerates NAD+ for glycolysis

86
Q

An overview of the Krebs cycle

A

In matrix under aerobic conditions.
Acetyl-CoA + 2H2O oxidative decarboxylated twice to form 2CO2, 3NADH, FADH, ATP

87
Q

Describe the Krebs cycle

A

Acetyl-CoA combines with oxaloacetate to form citrate (citrate synthase)
-> isocitrate (aconitase)
-> a-ketoglutarate, CO2, NADH (isocitrate dehydrogenase)
-> succinyl-CoA, CO2, NADH (a-ketogluterate dehydrogenase)
-> succinct + ATP (succinyl-CoA thiokinase)
-> fumarate + FADH (succinctly dehydrogenase)
-> malate (fumarase)
-> oxaloacetate + NADH (malate dehydrogenase)

88
Q

Krebs cycle regulators

A

ATP activates pyruvate dehydrogenase (link)
But inhibits first 3 Krebs enzymes

Most activated by substrate and inhibited by product

89
Q

Describe oxidative phosphorylation

A

NADH and FADH are oxidised to release H+ and e-. The e- pass down a series of electron carriers and energy released actively transports H+ into inter membrane space. H+ diffuses back into matrix through ATPsynthase which supplies energy for ATP formation. (O2 = terminal e- acceptor to form water)
= Forms 34 ATP

90
Q

What are the 3 steps of fatty acid breakdown?

A

Fatty acid activation
Fatty acid B-oxidation
Utilisation of Acetyl-CoA

91
Q

Describe fatty acid activation

A

Fatty acids are activated in cytoplasm before diffusing into mitochondria (Fatty acids with more than 14 carbons are actively transported)

Fatty acid + ATP -> ACYL Adenylate
+CoA-SH -> ACYL-CoA (acyl-CoA synthetase)

*NOT ACETYL

92
Q

Describe fatty acid B-oxidation

A

Oxidation -> Hydrolysis -> Oxidation -> Thiolysis
Each cycle produces 1 NADH, 1 FADH

Every cycle chops off 2C to produce an Acetyl-CoA. Therefore 12C chain produces 6 Acetyl-CoA
Fats = more energy rich than carbs

93
Q

Describe utilisation of Acetyl-CoA

A

Either most utilised via citric acid (TCA) cycle to produce glucose under normal metabolic conditions

Or produces ketones in liver when large amounts of Acetyl-CoA generated exceeds TCA cycle.

94
Q

Describe ketogenesis

A

2 Acetyl-CoA thiolysed to Acetoacetyl-CoA
-> HMG-CoA
-> Acetoacetate

Acetoacetate can spontaneously decarboxylate to acetone of enzymatically converted to B-hydroxybutyrate

(Utilised by all tissue but hepatic)

95
Q

Describe regulation of ketogenesis

A

Affected by free fatty acid release from adipose tissue, amount of glucagon or insulin
High ATP demand = more likely to oxidise Acetyl-CoA via TCA
Low conc of G-3-P in liver increases ketogenesis

96
Q

Describe diabetic ketoacidosis

A

Insulin deficiency
= Gluconeogenesis. + glycogenolysis
= Inhibition of Glycogen synthesis
Increased lipolysis

-> Hyperglycaemia + Increased Acetoacetate + beta-hydroxybutyrate

97
Q

Describe alcoholic ketoacidosis

A

Depleted protein and carbohydrate stores
= Decreased insulin
= Increased glucagon
= Decreased gluconeogenesis
= Increased lipolysis

-> Increased ketone production

98
Q

When does ketoacidosis occur?

A

In carbohydrate storages, heart + skeletal muscle utilise ketone bodies for energy, preserving glucose for the brain. Occurs in chronic alcohol abuse, type 1 diabetics and starvation.

99
Q

Consequences of ketoacidosis

A

Ketones are strong acids and lower blood pH
= Impairs ability of haemoglobin to bind to O2
Gets rid of CO2 = hyperventilating + fast respiration

Low pH, High O2, Low CO2, Low HCO3-

Phase 1 Notes (9 decks)

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