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ESA3 > ESA1 > Flashcards

ESA1 Flashcards

1
Q

Define energy

A

The capacity to do work

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2
Q

List the 9 essential amino acids that are required in the diet

A

Isoleucine, lysine, threonine, histidine, leucine, methionine, phenylalanine, tryptophan, valine

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3
Q

How is ATP stored for short term use in skeletal muscle?

A

Creatine + ATP -> phosphocreatine + ADP by enzyme ‘creatine kinase’

Reversed at times of need

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4
Q

Creatinine is a useful marker of GFR, what is it a breakdown product of?

A

Creatine and phosphocreatine

Breakdown at constant rate, proportional to musle mass
Algorithms to fix for race etc.

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5
Q

Why is fat important in the diet?

A

Vit ADEK are fat soluble so need fat
Storage of energy
Some fatty acids cannot be synthesised, e.g. Linoleic and linolenic acids

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6
Q

Briefly outline glycolysis

A

C6 -> (+2ATPs) -> p-C6-p -> C3 -> 2NADH, FADH2, 4ATP, 2C3 (pyruvate)

Intracellular process, takes place in cytosol
Include link reaction?

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7
Q

Important intermediates of glycolysis?

A 
Glycerol phosphate (made from DHAP via glycerol-3-phosphate dehydrogenase) 
Important in liver and adipose as needed for lipid synthesis

And 2,3-BPG (made from 1,3-BPG by enzyme bisphosphoglycerate mutase); important regulator of O2 affinity in RBC

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8
Q

Structure (big to small) and Features of skeletal muscle

A

Attached to bone via tendon
Fascia enveloping muscle
Epimysium enveloping bundles of fascicles
Perimysium enveloping one fascicle, containing nerves and blood vessels and muscle fibrils all travelling in parallel.
Endomysium surrounds muscle fibril, which consists of myofilaments

Peripherally displaced nuclei, striations, fused cells (mesodermally derived multipotent myogenic cells fused together).

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9
Q

Features of cardiac muscle

A 
Branching
Central nuclei
Intercalated disks
Desmosomes rivet cells together
Gap junctions electrically couple cells
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10
Q

How can creatine kinase be used to assess a patient with suspected MI?

A

Specific isoform of creatine kinase, (CK-MM 70%; CK-MB 30%), released by damaged myocytes few hours after MI

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11
Q

Describe structure of alpha helix

A 
Secondary structure
3.6 aa per turn
0.54 nm pitch
Right handed helix
NH group on one residue hydrogen bonds to C=O group 4 residues away
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12
Q

Describe structure of beta pleated sheet

A

0.35nm distance between adjacent amino acids

Parallel or antiparallel

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13
Q

How are amyloid fibres made

A

Usually soluble protein misfolded (beta sheet folded first) and becomes insoluble

Aggregates

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14
Q

Describe structure of collagen

A

Triple helix
Repeat of Gly-X-Y
Hydrogen bonds stabilise chains
Collagen fibrils formed from covalently cross-linking chains

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15
Q

Why does vitamin c deficiency result in scurvy?

A

Vit C is a co-factor for enzymes, prolyl hydroxylase and lysyl hydroxylase.

These enzymes hydroxylate proline (to hydroxyproline) and lysine (to hydroxylysine) in formation of procollagen.

This allows the cross linking that stabilises the triple helical structure

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16
Q

Sickle cell anaemia facts. Go.

A

Glu6 -> Val6
Valine is hydrophobic
Deoxyhaemoglobin therefore polymerise

More prone to lysis, because boomerang shape, and more rigid hence block microvasculature.

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17
Q

Why do beta thalassaemias present symptoms after birth?

A

Before birth, foetal haemoglobin in beta chains, hence faulty gene not yet expressed.
Alpha chains cant form stable tetramers!

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18
Q

Difference between fructosuria and fructose intolerance

A

Fructosuria simply means fructose in the urine, which is due to an absence of fructokinase

Fructose intolerance is far more serious, it is an absence of aldolase - which converts fr-1-p to GP

This leads to liver damage

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19
Q

Main polysaccharide in mammals and where?

A

Glycogen
Liver and skeletal muscle (more sm hence more there)
Alpha 1-4; 1-6(branches) glycosidic bonds

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20
Q

Main polymer of glucose in plants

A

Starch
Mixture of amylose and amylopectin
GI enzymes release glucose and maltose

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21
Q

Cellulose facts. Go.

A

Glucose polymer
Plants
Beta 1-4 linkages hence undigestable by humans

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22
Q

Enzymes involved in breakdown of dietary carbs

A

Saliva - Amylase
Pancreas - Amylase
Small intestine - Disaccharidases attached to brush border of epith cells. Lactase, sucrase, pancreatic amylase(a1-4), isomaltase (a1-6)

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23
Q

Which GLUT controlled by insulin

A

Glut 4

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24
Q

Why is glucose a major requirement in blood?

A

All tissues can metabolise glucose, and some NEED it

Rbc, wbc, kidney medulla, lens of eye

Cns prefers glucose

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25
Q

Pentose phosphate pathway function

A

Produce NADPH in cytoplasm (lipid synth, maintains free sulphydryl groups - cysteine)

Produce C5 sugars

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26
Q

Not enough O2, how regenerate NAD+

A

Lactate dehydrogenase

Produced by RBC, skeletal muscle
Released into blood
Normally metabolised by liver & heart

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27
Q

Lactate can be utilised by liver, via gluconeogenesis. Give examples of when this may not happen.

A

Impaired in liver disease
Vitamin deficiency - thiamine
Alcohol NAD+ -> NADH
Enzyme deficiencies

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28
Q

Glucose-6-phosphate dehydrogenase deficiency

A

Cant produce NADPH via Pentose Phosphate Pathway, hence heinz bodies in RBC; cataracts in eyes (free S-S not maintained)

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29
Q

Is Pentose phosphate pathway reversible

A

No

CO2 released

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30
Q

What is the link reaction

A

Pyruvate to Acetyl CoA

Using pyruvate dehydrogenase

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31
Q

How can a Vitamin B1 (thiamine) deficiency potentially cause serious issues (think about Pyruvate)

A

Pyruvate dehydrogenase is multi complex enzyme

Vit B1 = cofactor

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32
Q

Result of PDH deficiency (pyruvate dehydrogenase)

A

Lactic acidosis

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33
Q

How to stop final stage of catabolism?

A

Final stage is electron transport coupled to ATP synthesis

CN- stops electron acceptance by O2
Uncouplers increase permeability of mitochondrial inner membrane - dissipating proton gradient - e.g. Dinitrophenol, thermogenin

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34
Q

How do fluffy cute little hibernating animals stay warm?

A

They have brown adipose tissue, which contains thermogenin.

In response to cold, noradrenaline activates lipase -> fatty acids released, get oxidised, and activate thermogenin

Thermogenin transports H+ back in to mitochondria (dissipating the proton motive force), energy is released as heat (instead of ATP via ATP sythase)

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35
Q

Why does an oxygen binding curve for haemoglobin look sigmoidal vs myoglobin, which is hyperbolic?

A

Myoglobin binding simply dependent on oxygen concentration

Whereas deoxyhaemoglobin has two states - low affinity T, high affinity R.
O2 binding promotes stabilisation of R state. Co-operative binding - i.e. Binding affinity for oxygen increases as more o2 molecules bind to Hb subunits

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36
Q

What is 2,3-BPG and why is it important?

A

It is a regulator of O2 affinity (decreases), with one in every Hb tetramer in RBC.

formed from glycolysis intermediate, 1,3-BPG, via enzyme bisphosphoglycerate mutase

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37
Q

Bohr effect

A

Binding of H+ and CO2 lowers affinity of Hb for oxygen

Hence metabolically active tissues get O2 required

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38
Q

Why is CO poisonous?

A

Binds to Hb 250x more readily than O2
Fatal when COHb >50%
Weirdly, it increases affinity for oxygen of unaffected subunits

But basically, not enough free Hb to carry required amount of O2

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39
Q

What is special about foetal haemoglobin?

A

HbF has higher binding affinity for O2 vs HbA hence allows transfer of O2 from mother

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40
Q

Binding of subtrates can induce changes in conformation of enzyme

What hypothesis am I talking about?

A

Induced Fit

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41
Q

What is the Michaelis-Menten model for enzyme catalysis?

A

A model that proposes that a specific complex between enzyme and substrate is a necessary intermediate in catalysis

Basically, Vo versus [S] will be a rectangular hyperbola

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42
Q

In Mic-menten kinetics, what is Vmax?

A

The maximal rate of reaction when all enzyme active sites are saturated with substrate

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43
Q

In mic-menton kinetics, what is Km?

A

The subtrate concentration that gives half maximal velocity of reaction

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44
Q

Km values give a measure of affinity of an enzyme for its subtrate. What affinity if low Km?

A

High affinity

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45
Q

Km values give a measure of affinity of an enzyme for its subtrate. What affinity if high Km?

A

Low affinity

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46
Q

Hexokinase - tissues
Glucokinase - liver

What is the difference?

A

Hexokinase has a lower Km, hence is always active

Glucokinase has higher Km, hence only becomes active when glucose levels peak after feeding

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47
Q

Activity of an enzyme is measured in…

A

Amount of enzyme that converts 1MICROmol of product per min under standard conditions

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48
Q

You have a lineweaver burk plot. Which intercepts indicate which values in terms of enzyme kinetics?

A

X intercept= 1/Km

Y intercept = 1/Vmax

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49
Q

How do competitive and non-competitive inhibitors differ in the way they affect Km and Vmax?

A

Comp affects Km not Vmax

Non comp vice versa

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50
Q

What is a nucleosome

A

DNA wrapped around octamer of histones- 2 of each:
H2a/b, h3,h4

H1 then is the ‘clip’ that stabilises

51
Q

Heterochromatin vs euchromatin

A

Heterochromatin genes not expressed

Eu genes expressed

52
Q

What is a genome?

A

Entire DNA sequence

53
Q

Difference between nucleoside and nucleotide?

A

Base and sugar is nucleoside

Base, sugar and phosphate is nucleotide

54
Q

Types of nitrogenous bases found in DNA (and RNA)

A

Adenine, guanine - purines

Cytosine, thymine - pyrimidines (uracil in RNA)

55
Q

How is a phosphate attached to the ribose sugar in a nucleotide?

A

Phosphate ester link on carbon 5

56
Q

Nucleotides are joined via …

A

Phosphodiester bonds, 5’-3’ polarity

57
Q

Base pairs DNA (RNA)

A

Adenine // Thymine (Uracil)

Guanine /// Cytosine

58
Q

Where can we see RNA stem loops?

A

Hydrogen bonds formed between anti-parallel complementary sequences,

Found in tRNA

59
Q

What reaction is catalysed by DNA polymerase?

A

(dNMP)n + dNTP -> (dNMP) n+1 + PPi

Reaction driven by pyrophosphate hydrolysis

60
Q

Three steps DNA replication prokaryotes

A

1) initiation
2) elongation
3) termination

61
Q

What are okazaki fragments and why do they occur in DNA replication?

A

Because DNA polymerise works 5’-3’, hence primase needed so it can work - but in fragments

But DNA ligase needed to connect backbone

62
Q

What is it about meiosis that generates genetic diversity?

A
  1. Random assortment of chromosomes

2. Crossing over of genetic material

63
Q

Difference in meiosis of gametes male and female?

A

Male one spermatogonium = 4 mature sperm

Female one oocyte = 1 egg + 3 polar bodies

64
Q

Example of autosomal recessive disease?

A

Cystic fibrosis

65
Q

Example of autosomal dominant disease?

A

Huntingtons

66
Q

Example of x-linked recessive disease?

A

Haemophilia A

67
Q

Co-dominance genetic example

A

Blood groups

68
Q

Linkage and recombination

A

Look it up

69
Q

Give an example of a promoter sequence in prokaryotes and eukaryotes

A

Tata box prok

Prinbow box in euk?

70
Q

Rna processing?

A

Capping (5’ cap protects against degradation)

Tailing/Polyadenylation (at 3’ end, “)

Splicing in the middle removes introns, sequence dependent

71
Q

What do I need to make a polypeptide?

A

Ribosome, amino acids (substrate), mRNA (template),

Initiation elongation termination

72
Q

What types of ribosomes euk prok

A

Euk 80s

Prok 70s

73
Q

Initiation codon

A

AUG

Codes for methionine

74
Q

What is a wobble position when it comes to tRNA?

A

5’ end of anticodon
3’ end of codon

Basically, there is a degree of flexibility here
One mrna could read multiple codons

75
Q

How are tRNA molecules activated?

A

tRNA synthetase

76
Q

Briefly describe translation in prokaryotes.

A

Initiation using AUG codon, methionyl tRNA brought to ribosome P site.

Next codon read, appropriate amino acyl tRNA brought to A site.

Peptidyl transferase forms peptide bond between both amino acids, leaving P site free.

Translocation of polypetide to P site, cycle repeats.

To terminate, stop codon allows water to be brought.

77
Q

In which direction does protein synthesis occur?

A

N -> C

78
Q

What is the mechanism behind pyruvate dehydrogenase deficiency?

A

Mutation that results in Arg to Pro substitution,
Hence ruins signal?
Less uptake in to mitochondria

Lactic acidosis, neurological problems

79
Q

PCR

A

Uodhaefeajfjfo

80
Q

Types of single base mutations

A

Missense - one amino acid substituted for another
Silent - no substitute of amino acid
Nonsense - STOP instead of amino acid (little or no protein may be made due to nonsense mediated decay - protective mechanism)
Frameshift - reading frame of mRNA altered (“)

81
Q

Failure of DNA repair mechanisms can result in cancer. What genes are commonly mutated in cases of hereditary non-polyposis colorectal cancer?

A

MSH2 in 60% of families

82
Q

Formation of a tumour needs 6 things. List them.

A

1) divide independently of external growth signals
2) ignore external antigrowth signals
3) avoid apoptosis
4) divide indefinitely without senescence
5) stimulate sustained angiogenesis
6) invade tissues and establish secondary tumours

83
Q

What is epigenetic modification?

A

Genes only expressed from active chromatin

DNA demethylation, histone acetylation etc. can switch heterochromatin to euchromatin, without changing the actual DNA sequence itself. This is epigenetics.

84
Q

Chromosome morphology key words. Go.

A

P arm is petit, q is long

85
Q

Causes of aneuploidy

A

Non disjunction at one of the meiotic divisions
Forms gametes with missing and extra chromosomes

If occurs due to mitotic cell division, causes mosaicism

Or anaphase lag, chromosomes left behind in cell

86
Q

Why is uniparental disomy a problem?

A

Imprinting, maternal and paternal chromosomes behave differently

87
Q

Beta oxidation of fatty acids is NOT found in which tissues?

A

Brain
Rbc
Wbc

88
Q

Briefly outline beta oxidation of fatty acids.

A

Mitochondrial
First activation, then carnitine to mitochondria
Cycle of reactions
Removal of 2c units per cycle
Stops in absence of O2
H+ and e- transferred to NAD+ and FAD, no ATP synthesis

89
Q

TAG broken down in to Glycerol and Fatty acids. Fatty acids have undergone beta oxidation, what happens to glycerol?

A

Liver
Glycerol kinase-> glycerol phosphate

Can either be converted to DHAP and back into glycolysis
Or
TAG synthesis

90
Q

Glycogenesis and glycogenolysis describe

A

Glucose hexokinase glucose 6 phosphate

Phosphoglucomutase - glucose1phosphate

Glycogen synthase or branching enzyme

To break down, glycogen phosphorylase and debranching enzyme (dif enzyme hence dif regulation). At end, G-6-P phosphatase in liver converts back to glucose

91
Q

Difference in function of glycogen stores in liver and skeletal muscle?

A

G6P converted to glucose in liver using enzyme G6Phosphatase.

Enzyme not present in skeletal muscle, hence straight to glycolysis

92
Q

Three major precursors of gluconeogenesis

A

Lactate (cori cycle)
Glycerol
Amino acids

93
Q

Why can’t Acetyl~CoA be converted to glucose?

A

Because pyruvate dehydrogenase reaction is irreversible

94
Q

Key enzymes in gluconeogenesis?

A

1) PEPCK
2) Fructose 1,6 bisphosphatase
3) Glucose-6-Phosphatase

95
Q

Glucogenic and ketogenic amino acids

Both?

A

Glucogenic glycine
Ketogenic Lysine
Both Phenylalanine

96
Q

What is the cause of refeeding syndrome?

A

Urea cycle enzyme levels matched with demand to dispose of ammonia - i.e. High protein diet.

Low protein diet / starvation represses levels,

cycle is inducible however, hence refeed gradually. Build up in a week.

97
Q

Why is ammonia toxic?

A

Interferes with amino acid transport and protein synthesis

pH effects

Alteration of blood brain barrier

Inteferes TCA cycle

98
Q

Phenylketonuria

A

Deficiency in phenylalanine hydroxylase (convrts phen to tyrosine)

Aut recess. Chromosome 12
Accumulation of phenylalanine in tissues, plasma and urine

Phenylketones in urine

Affects norad, ad, dopa, mel, thyroid, prot synth.
Symptoms: severe intellectual disability, developmental delay, microcephaly, seizures, hypopigmentation

99
Q

Homocystinurias

A

Normally, methionine conv to homocysteine to cystathionine and finally cysteine (enzyme: CYSTATHIONINE BETASYNTHASE)

Problem breaking down methionine because no enzyme
Excess homocystine (oxidised form of homocysteine) in urine
100
Q

Why is cholesterol important?

A

Essential membranes
Steoid hormone precursor
Bile acid precursor

101
Q

A 3 year old girl is admitted with fever, tachypnoea (rapid breathing), photophobia, neck stiffness and a non-blanching rash. Meningitis is suspected. A lumbar puncture is performed.
Q1. Suggest a suitable vertebral level at which the needle should be inserted. Explain the rationale for your choice.
Q2. State the structures through which the needle will pass through, in order from the skin to the subarachnoid space.

A

L2/3), L3/4 or L4/5 (after the conus medullaris so only mobile spinal nerve roots not cord; least chance of neurological damage)

• (Skin), subcutaneous tissue,
supraspinous ligament, interspinous
ligament, ligamentum flavum, epidural fat and veins, dura mater,
arachnoid mater, (subarachnoid space)

102
Q

Atheroma

A

Accumulation of intra/extra cellular lipid in the intima and media of large and medium sized arteries

103
Q

Define atherosclerosis vs arteriosclerosis

A

Thickening and hardening of arterial walls as a consequence of atheroma

Whereas arteriosclerosis is the thickening of walls of arteries and arterioles usually as a result of hypertension or diabetes mellitus

104
Q

Common sites for atheroma

A

Aorta especially abdominal

Coronary arteries

Carotid arteries

Cerebral arteries

Leg arteries

105
Q

Normal arterial structure

A

Endothelium

Sub endothelial c.t.

Internal elastic lamina

Muscular media

External elastic lamina

Adventitia

106
Q

Microscopic features of atheroma

A

Early changes:
Proliferation of smooth muscle cells
Accumulation of foam cells
Extra cellular lipid

Later:
Fibrosis 
Necrosis
Cholesterol clefts 
\+/- inflammatory cells 
\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
Eventually 
Disruption of internal elastic lamina
Damage extends into media
Ingrowth of blood vessels
Plaque fissuring
107
Q

Virchow’s triad?

A

Endothelial injury

InflammationsjsjxgsizmxakcnznKzn Bc

Increased permeability to lipid from plasma

108
Q

Briefly explain how atheromas are formed?

A

Endothelial injury due to
Raised LDL/toxins/hypertension/haemodynamic stress

Causes
Platelet adhesion, SMC proliferation and migration/insudation of lipid/LDL oxidation/migration of monocytes into intima

Stimulated SMC produce matrix material

Macrophages engulf lipids and become foam cells - they then secrete cytokines causing further SMC stimulation and recruitment of other inflammatory cells

109
Q

Why doesn’t newly synthesised fatty acid immediately get transported to mitochondria and oxidised?

A

Because malonyl CoA inhibits the carnitine shuttle

110
Q

What are the different classes of hormones and give an example of each.

A

Peptide hormones - insulin, glucagon, growth hormones

Amino acid derivatives - adrenaline, noradrenaline, thyroid hormones

Glycoproteins - LH, FSH, TSH

Steroids - cortisol, aldosterone, testosterone

111
Q

Steroid hormones are synthesised from cholesterol

A
  • Aldosterone
  • Testosterone
  • Progesterone
  • Cortisol
112
Q

How is the hypothalamus connected to the pituitary

A

Directed connected to the posterior pituitary gland since hypothalamus drops down through the infundibulum to form posterior pituitary

113
Q

Basic outline of regulation of blood calcium levels.

A

When Ca2+ low, PTH from PTG chief cells: Stimulates bone resorption, increases kidney reabsoprtion, decreases kidney reabsorption of phosphate. Also indirectly affects absorption via Vit D activation through kidneys.

Vit D -> calcitriol: increases ca absorption in gut, more bone resor., less urinary loss.

If high: Calcitriol - by parafollicular cells of THYROID! Not so relevant in humans.

114
Q

What does hypercalcaemia lead to?

A 
Stones moans (depression) and groans (abdo pain)
Ttmt: fluids and surgery to remove parathyroid tumour
115
Q

Glut transporters?

A

GLUT1 - RBC, BBB: low level basal glucose uptake for resp

GLUT2 - Two way, liver and b-cells of pancreas

GLUT3 - vv high affinity, brain

GLUT 4 - regulated by insulin. Skeletal muscle, adipose

116
Q

acetaminophen(paracetamol) overdose, why is it dangerouus and what ttmt?

A

Normally paracetamol combined with sulphate. Okay.
High doses -> becomes NAPQI (toxic!), which uses up glutathione.

Acetylcysteine replenishes liver glutathione levels

117
Q

Patent ductus arteriosus

A

Ductus arteriosus is present in foetus to shunt blood from pulmonary artery to aorta. Should close after birth, but if open blood flow will be from high to low pressure.

Mechanical murmur heard.
HOWEVER chronic shunting -> vascular remodelling, increase pulmonary resistance, MAY reverse!

118
Q

Coarctation of the aorta

A

Narrowing of aortic lumen in region of ligamentum arteriosum. Narrowing increases afterload on left ventricle, left vent hypertrophy.

Upper limb branches prior to coarctation, hence lower limb femoral pulse weakened with upper hypertension

119
Q

Tetralogy of fallot

A

1) VSD
2) Overriding aorta
3) pulmonary stenosis
4) right ventricular hypertrophy

120
Q

Transposition of the great arteries

A

Not compatible with life after birth

Shunt must be created until surgery

121
Q

What is stroke volume?

A

End Diastolic Volume - End Systolic Volume

122
Q

Describe process of insulin synthesis and rlease from b cell of islet.

A

mRNA translated as one polypeptide: preproinsulin
Preproinsulin enters ER and has signal peptide cleaved, leaving proinsulin.

Proinsulin passes through golgi and is exposed to several specific endopeptidases, which excise the C-peptide- leaving insulin and C-peptide.

Insulin stays in cell until glucose comes in (GLUT2) and enters glycolysis, synthesis of ATP inhibits an ATP-sensitive potassium channel, reducing K+ efflux. This leads to depolarisation of the cell - and the v-gated Ca2+ channel opens. Ca2+ enters, inducing exocytosis of the insulin.

123
Q

Difference between fecundity and fertility

A

Fecundity = physical ability to reproduce

Fertility = realisation of this potential as births

ESA3 (7 decks)

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