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Part 1 MRCOG > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

Enzyme for synthesis of catecholamines

A

catecholamine-O- methyltransferase

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2
Q

Glucocorticoids are produced from which part of the adrenal cortex?

A

Zona fasciculata

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3
Q

Mineralocorticoids produced from which part of adrenal cortex?

A

Zona glomerulosa

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4
Q

In prostaglandins, which carbon position is the hydroxyl group?

A

C15

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5
Q

How many carbons does oestrogen/ progesterone/ prostaglandins/ androgen have?

A

Oestrogen: 18
Progesterone: 21
Prostaglandins: 20
Androgen: 19

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6
Q

Where are prostaglandins deactivated and with what enzyme?

A

Lungs, cyclo-oxygenase

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7
Q

Enzymes required for ammonia production

A

glutaminase, glutamate dehydrogenase

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8
Q

Site of urea production in the body

A

Liver

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9
Q

Function of G6PD enzyme
(Glucose 6 phosphate dehydrogenase)

A

NADPH production in RBCs.

Catalyses glucose 6 phosphate conversion to 6 phosphogluconate

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10
Q

Enzyme responsible of rconversion of glucose 6 phosphate to fructose 6 phosphate

A

Phosphoglucose isomerase

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11
Q

Enzyme responsible for glucose phosphorylation to glucose 6 phosphatase

A

Glucokinase

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12
Q

Enzyme responsible for ATP production from ADP and phosphate

A

ATP synthase

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13
Q

Enzyme required for acrosomal reaction

A

Hyaluronidase (breaks down hyaluronic acid- allowing sperm to penetrate the egg)

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14
Q

What precedes mitosis? (Cell cycle)

A

G2

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15
Q

How does smoking affect fetal brain development?

A

Nicotine crosses placental barrier. Nicotine affects brain development because it stimulates nicotinic acetylcholine receptors (nAChRs); in the immature brain, acetylcholine, plays a critical neurotrophic role in determining the patterns of cell development

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16
Q

Function of BRCA

A

Tumour suppressor gene- produces proteins that help repair damaged DNA

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17
Q

Precursor of serotonin

A

Tryptophan

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18
Q

Phosphate is excreted by?

A

Kidneys

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19
Q

Where is most HCO3- reabsorbed?

A

Proximal convoluted tubule

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20
Q

Site where active Vit D is produced?

A

Kidney

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21
Q

Which enzyme catalyses the rate-limiting step in the urea cycle?

A

Carbamoyl phosphate synthetase

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22
Q

Excessive use of vitamin E presents with

A

Haemorrhage

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23
Q

Active form of vitamin D

A

1, 25 dihydroxy-chloecalciferol

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24
Q

Enzyme that converts diaclyglycerol to arachidonic acid

A

Phospholipase C

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25
Q

Absorption of which vitamin/ mineral is hampered by oxalic acid & phytate?

A

Calcium

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26
Q

Vitamin C plays an important role in which biochemical process?

A

Collagen synthesis

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27
Q

Glucose 6 phosphatase plays an important role in

A

Gluconeogenesis (catalyses terminal step- converting glucose 6 phosphate to glucose)

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28
Q

Pellagra is a vitamin deficiency that leads to diarrhoea, dementia and dermatitis. Which vitamin is deficient?

A

Niacin

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29
Q

What is the pathophysiological mechanism by which vitamin A excess can cause congenital anomalies?

A

Ectopic induction of gene expression (an abnormal gene expression in a cell type, tissue type, or developmental stage in which the gene is not usually expressed)

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30
Q

Active form of vitamin A

A

Retinoic acid

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31
Q

Prostaglandin synthesis: from what molecule/ pathways and first one to be made

A

Made from arachidonic acid (C20)

Cyclo-oxygenase pathway and lipoxygease pathway

1st one is prostaglandin H2 (from cycle-oxygenase pathway)

32
Q

Which molecules can be metabolised by glycolysis?

A

Glucose, fructose and galactose only

33
Q

Function of glucose-6-phosphate dehydrogenase (G6PD)

A

Key and rate limiting enzyme in pentose phosphate pathway

34
Q

Vitamin K is essential for the synthesis of what?

A

Clotting factors (1972): X (10), IX (9), VII (7), II (2)
Protein C, S and Z
Osteocalcin and GLA proteins

35
Q

What shifts the oxygen dissociation curve to the right

What shifts the oxygen dissociation curve to the left

Where does the oxygen dissociation curve sit for Fhb compared to adults?

A

Right (lower affinity for O2- hence releases it into tissues):
Increased temperature
Increased H+ (acidosis)
Increased 2,3 DPG
Increased pCO2

Left (higher affinity for O2, so doesn’t release into tissues):
Increasing pCO
Decreased temperature
Decreased H+ (alkalosis)
Decreased 2,3 DPG

The oxygen dissociation curve for fetal haemoglobin lies to the left of the normal adult oxygen dissociation curve as it has a higher affinity for Oxygen.

36
Q

What is fibrinogen activated by?

A

Thrombin

37
Q

hCH patterns for normal viable IUP, molar pregnancy, ectopic pregnancy or twin pregnancy

A

Viable IUP: should rise by 66% every 48h (>63%)

Molar: very high hCG. Partial molar- hCG rises at a slower rate and to a lower level than expected for a normal pregnancy

Ectopic: hCG levels tend to plateau or have a doubling time of >7 days

Twins: typically higher than for IUP

38
Q

What are the 3 ketone bodies?
Which one can be used for heart energy?

A

Acetone
Beta- hydroxybutyric acid
Acetoacetic acid

Acetoacetic acid and beta-hydrocxbutyric acid can be utilised by brain, heart and muscles

39
Q

Progesterone levels: what do RCOG/ NICE say regarding viable/ non-viable pregnancies

A

NICE: advise do not use serum progesterone to diagnose viable IUP or ectopic

RCOG: advised progesterone <20nmol/L strongly suggestive of non-viable pregnancy and levels >60nmol/L suggestive of IUP

40
Q

Interpretation of serial bhCGs

A

Decrease in hCG >50%: Pregnancy unlikely to continue. PT in 14 days.

Change between 50% decline and 63% increase:
Review again within 24h

Increase >63%: Likely IUP, offer scan in 7-14 days or earlier if hCG >1500 IU/ L

41
Q

What are caherins?

A

Calcium ion dependent adhesion molecules- they bind cells together via adhering junctions.

Main role = cell adhesion
Transmembrane proteins

42
Q

What are selectins?

A
  • Cell adhesion molecules
  • Glycoproteins
  • Bind to leucocytes with catch and slip weak bones
  • Play a role in inflammation attracting leucocytes

Three types:
E- selection: in endothelial cells
L- selectin: in lymphocytes
P- selectin: in platelets

43
Q

What are integrins?

A

Transmembrane receptors
Play a role in signal transduction between cell and extracellular matrix
Also attach cell to the ECM

One example is fibronectin

44
Q

Causes of prolonged PT (prothrombin time) and INR

A
  • Factor V deficiency
  • Warfarin
  • Liver failure
  • DIC
45
Q

Mitosis phases

A

Prophase: chromatin condenses to chromosomes (paired as chromatids). Mitotic spindle forms.

Metaphase: Chromatids align at the equatorial plan (AKA metaphase plate)

Anaphase: Chromatids pulled apart into 2 constituent daughter chromosomes

Telophase: New nuclear envelopes form around each daughter chromosome

Cytokinesis: cells divide

46
Q

Cell cycle

A

G0- resting phase
G1- interphase (cells increase in size)
S- Interphase (DNA replication)
G2- interphase (Cells increase in size
M- Mitosis

47
Q

A number of cytogenetic methods can be employed in the prenatal genetic screening.

  1. Which screening method examines interphase chromosomes?
  2. What is the standard test used for conventional cytogenetic analysis of human chromosomes?
A
  1. FISH (Fluorescence in situ hybridization)
  2. G banding
48
Q

Which key cellular ‘second messenger’ signalling molecule is generated from precursor amino acid L arginine?

A

Nitric oxide

49
Q

3 Major pathways involved in ATP production & how many molecules of ATP/ NADH from one glucose?

A

Glycolysis
Krebs/ TCA cycle
Electron transport system

2 ATP & 2 NADH from glycolysis
2 ATP, 6 NADH and 2 FADH2 from TCA
34 ATP from ETC

Total = 38 ATP

50
Q

What is the role of glucose-6-phosphatase?

A

Final step in gluconeogenesis

51
Q

Which enzyme is involved in the rate limiting step of glycolysis?

A

Phosphofructokinase

52
Q

Essential fatty acids

A

Both unsaturated:

Linoleic acid (18C and 2 double bonds, omega 6)

Linolenic acid (18C and 3 double bonds, omega 3)

53
Q

What is the urea cycle?

Where does it take place?

A

An essential metabolic pathway that removes nitrogenous waste produced by the breakdown of proteins and other nitrogenous compounds

1x Ammonia and 1x CO2 are consumed. Urea is produced.

Mitochondria & cytosol of liver cells

54
Q

How do nitrogen’s from amino acids enter the urea cycle?

A

As carbamoyl phosphate

55
Q

Aspirin and NSAIDS are often contraindicated in individuals with asthma. The activity of which enzyme can exacerbate airway inflammation in such individuals?

A

Lipooxygenase

56
Q

Which 2nd messenger signalling molecule is generated by oxytocin stimulation of myometrial myocytes and stimulation of intracellular Ca+2 release?

A

IP3

57
Q

Phenylketonuria
- Incidence
- Inheritance/ genetic abnormality
- Clinical significance
- Testing
- Treatment

A

1 in 10,000

Autosomal recessive, chromosome 12

Phenylalanine hydroxylase deficiency = impaired phenylalanine –> tyrosine conversion, so phenylpyruvate, phenyl acetate and phenyllactate accumulate

Clinically- seizures, cognitive impairment/ microcephaly

Mx: Dietary regimen- low phenylalanine/ sufficient tyrosine and other AAs

58
Q

Which part of the nephron activiely excretes H+

A

PCT & DCT

59
Q

Normal values of pH, BE for umbilical artery/ vein at term

A

Artery (de-oxy)
pH 7.1-7.38
BE -9.9 to 1.8

Vein (oxygenated)
pH 7.2-7.44
BE -7.7 to 1.9

60
Q

Where does the chloride shift phenomenon occur?

A

RBC

61
Q

Average Hb concentration in a new born at term

A

15g/ dl

62
Q

Which amino acid contributes to formation of ammonia in kidney?

A

Glutamine

63
Q

Hydrogen ion buffer in interstitial space

A

Bicarbonate

64
Q

Function of smooth ER

A

Lipid synthesis and detoxification of certain drugs

65
Q

What is the GTP binding protein, which, when bound by GTP, induces formation of cAMP

A

Gas

66
Q

Why can’t fats be converted to carbohydrates?

A

The pyruvate dehydrogenase reaction is irreversible (makes Acetyl CoA from pyruvate + CO2) and the CO2 is subsequently lost in the TCA cycle

67
Q

Initial investigations for amenorrhoea (NICE)

A

Pelvic US
UPT
Serum prolactin
TSH
FSH/ LH
Oestradiol
Total testosterone
Coeliac disease screen

68
Q

Clinical features of magnesium toxicity

A

Loss of deep tendon reflexes
Respiratory depression
Facial flushing
Low BP

Magnesium is mostly excreted in urine, so halt infusion if urine output <20ml/h

69
Q

Which vitamin is a co-enzyme in the rate-limiting step in haemoglobin synthesis?

A

Vitamin B6

70
Q

Where does fatty acid synthesis occur within the cell?

A

Cytosol

71
Q
A
72
Q

Site of thromboxane A2 synthesis

A

Platelets

73
Q

Fat soluble vitamin synthesised by large intestinal bacteria

A

Vit K

74
Q

Essential/ non-essential AAs

A

Essential:
(Any) (Arginine)*
Help Histidine
In Isoleucine
Learning Leucine
These Threonine
Little Lysine
Molecules Methionine
Proves Phenylalanine
Truly Tryptophan
Valuable Valine

*Arginine is only essential in times of positive nitrogen balance

Non-essential:
Alanine
Asparagine
Aspartic acid
Glutamic acid
Serine

75
Q

Endocrine
Exocrine
Paracrine
Autocrine signalling

A

Endocrine: secrete substances into bloodstream

Exocrine: secrete substances into a ductal system to an epithelial surface

Paracrine: Release of hormones to act on local cells

Autocrine: cell receiving signal secreted by itself

Part 1 MRCOG (13 decks)

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