Biochemistry Flashcards
Enzyme for synthesis of catecholamines
catecholamine-O- methyltransferase
Glucocorticoids are produced from which part of the adrenal cortex?
Zona fasciculata
Mineralocorticoids produced from which part of adrenal cortex?
Zona glomerulosa
In prostaglandins, which carbon position is the hydroxyl group?
C15
How many carbons does oestrogen/ progesterone/ prostaglandins/ androgen have?
Oestrogen: 18
Progesterone: 21
Prostaglandins: 20
Androgen: 19
Where are prostaglandins deactivated and with what enzyme?
Lungs, cyclo-oxygenase
Enzymes required for ammonia production
glutaminase, glutamate dehydrogenase
Site of urea production in the body
Liver
Function of G6PD enzyme
(Glucose 6 phosphate dehydrogenase)
NADPH production in RBCs.
Catalyses glucose 6 phosphate conversion to 6 phosphogluconate
Enzyme responsible of rconversion of glucose 6 phosphate to fructose 6 phosphate
Phosphoglucose isomerase
Enzyme responsible for glucose phosphorylation to glucose 6 phosphatase
Glucokinase
Enzyme responsible for ATP production from ADP and phosphate
ATP synthase
Enzyme required for acrosomal reaction
Hyaluronidase (breaks down hyaluronic acid- allowing sperm to penetrate the egg)
What precedes mitosis? (Cell cycle)
G2
How does smoking affect fetal brain development?
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
Function of BRCA
Tumour suppressor gene- produces proteins that help repair damaged DNA
Precursor of serotonin
Tryptophan
Phosphate is excreted by?
Kidneys
Where is most HCO3- reabsorbed?
Proximal convoluted tubule
Site where active Vit D is produced?
Kidney
Which enzyme catalyses the rate-limiting step in the urea cycle?
Carbamoyl phosphate synthetase
Excessive use of vitamin E presents with
Haemorrhage
Active form of vitamin D
1, 25 dihydroxy-chloecalciferol
Enzyme that converts diaclyglycerol to arachidonic acid
Phospholipase C
Absorption of which vitamin/ mineral is hampered by oxalic acid & phytate?
Calcium
Vitamin C plays an important role in which biochemical process?
Collagen synthesis
Glucose 6 phosphatase plays an important role in
Gluconeogenesis (catalyses terminal step- converting glucose 6 phosphate to glucose)
Pellagra is a vitamin deficiency that leads to diarrhoea, dementia and dermatitis. Which vitamin is deficient?
Niacin
What is the pathophysiological mechanism by which vitamin A excess can cause congenital anomalies?
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)
Active form of vitamin A
Retinoic acid
Prostaglandin synthesis: from what molecule/ pathways and first one to be made
Made from arachidonic acid (C20)
Cyclo-oxygenase pathway and lipoxygease pathway
1st one is prostaglandin H2 (from cycle-oxygenase pathway)
Which molecules can be metabolised by glycolysis?
Glucose, fructose and galactose only
Function of glucose-6-phosphate dehydrogenase (G6PD)
Key and rate limiting enzyme in pentose phosphate pathway
Vitamin K is essential for the synthesis of what?
Clotting factors (1972): X (10), IX (9), VII (7), II (2)
Protein C, S and Z
Osteocalcin and GLA proteins
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?
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.
What is fibrinogen activated by?
Thrombin
hCH patterns for normal viable IUP, molar pregnancy, ectopic pregnancy or twin pregnancy
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
What are the 3 ketone bodies?
Which one can be used for heart energy?
Acetone
Beta- hydroxybutyric acid
Acetoacetic acid
Acetoacetic acid and beta-hydrocxbutyric acid can be utilised by brain, heart and muscles
Progesterone levels: what do RCOG/ NICE say regarding viable/ non-viable pregnancies
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
Interpretation of serial bhCGs
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
What are caherins?
Calcium ion dependent adhesion molecules- they bind cells together via adhering junctions.
Main role = cell adhesion
Transmembrane proteins
What are selectins?
- 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
What are integrins?
Transmembrane receptors
Play a role in signal transduction between cell and extracellular matrix
Also attach cell to the ECM
One example is fibronectin
Causes of prolonged PT (prothrombin time) and INR
- Factor V deficiency
- Warfarin
- Liver failure
- DIC
Mitosis phases
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
Cell cycle
G0- resting phase
G1- interphase (cells increase in size)
S- Interphase (DNA replication)
G2- interphase (Cells increase in size
M- Mitosis
A number of cytogenetic methods can be employed in the prenatal genetic screening.
- Which screening method examines interphase chromosomes?
- What is the standard test used for conventional cytogenetic analysis of human chromosomes?
- FISH (Fluorescence in situ hybridization)
- G banding
Which key cellular ‘second messenger’ signalling molecule is generated from precursor amino acid L arginine?
Nitric oxide
3 Major pathways involved in ATP production & how many molecules of ATP/ NADH from one glucose?
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
What is the role of glucose-6-phosphatase?
Final step in gluconeogenesis
Which enzyme is involved in the rate limiting step of glycolysis?
Phosphofructokinase
Essential fatty acids
Both unsaturated:
Linoleic acid (18C and 2 double bonds, omega 6)
Linolenic acid (18C and 3 double bonds, omega 3)
What is the urea cycle?
Where does it take place?
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
How do nitrogen’s from amino acids enter the urea cycle?
As carbamoyl phosphate
Aspirin and NSAIDS are often contraindicated in individuals with asthma. The activity of which enzyme can exacerbate airway inflammation in such individuals?
Lipooxygenase
Which 2nd messenger signalling molecule is generated by oxytocin stimulation of myometrial myocytes and stimulation of intracellular Ca+2 release?
IP3
Phenylketonuria
- Incidence
- Inheritance/ genetic abnormality
- Clinical significance
- Testing
- Treatment
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
Which part of the nephron activiely excretes H+
PCT & DCT
Normal values of pH, BE for umbilical artery/ vein at term
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
Where does the chloride shift phenomenon occur?
RBC
Average Hb concentration in a new born at term
15g/ dl
Which amino acid contributes to formation of ammonia in kidney?
Glutamine
Hydrogen ion buffer in interstitial space
Bicarbonate
Function of smooth ER
Lipid synthesis and detoxification of certain drugs
What is the GTP binding protein, which, when bound by GTP, induces formation of cAMP
Gas
Why can’t fats be converted to carbohydrates?
The pyruvate dehydrogenase reaction is irreversible (makes Acetyl CoA from pyruvate + CO2) and the CO2 is subsequently lost in the TCA cycle
Initial investigations for amenorrhoea (NICE)
Pelvic US
UPT
Serum prolactin
TSH
FSH/ LH
Oestradiol
Total testosterone
Coeliac disease screen
Clinical features of magnesium toxicity
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
Which vitamin is a co-enzyme in the rate-limiting step in haemoglobin synthesis?
Vitamin B6
Where does fatty acid synthesis occur within the cell?
Cytosol
Site of thromboxane A2 synthesis
Platelets
Fat soluble vitamin synthesised by large intestinal bacteria
Vit K
Essential/ non-essential AAs
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
Endocrine
Exocrine
Paracrine
Autocrine signalling
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
