Biochemistry

Question 1

Where in the cell contains circular DNA?

Answer 1

Mitochondria - contains its own genome

Question 2

What is the difference between wet and dry beriberi?
What is the nutritional deficiency

Answer 2

Wet = heart failure present
Dry = just peripheral neuropathy
Thiamine deficiency

Question 3

What is the diagnostic test for cystinuria?

Answer 3

Cyanide Nitroprusside

Question 4

Where in the cell does
- metabolism
- protein synthesis occur?

Answer 4

Cytoplasm

Question 5

Where in the cell does protein modification occur?

Answer 5

Endoplasmic Reticulum

Question 6

Where in the cell does protein processing occur?

Answer 6

Golgi apparatus

Question 7

Where in the cell does protein degradation occur?

Answer 7

Lysosome

Question 8

What part of the cell cycle does the cell spend the most time in?

Answer 8

G1

Question 9

When is DNA replicated?

Answer 9

Synthesis

Question 10

Fates of absorbed glucose (3)

Answer 10

Glycolysis
Storage as glycogen
Converted to triglycerides/amino acids/lipids

Question 11

Where does glycolysis occur?
What is the aim of glycolysis?

Answer 11

Cytoplasm
Make ATP and NADPH available
Produces pyruvate - intermediary

Question 12

Hexokinase vs glucokinase

Answer 12

Glucokinase is when glucose is oxidised in the liver

Question 13

Where in the cell does gluconeogenesis occur?

Answer 13

Cytoplasm

Question 14

Explain pentose phosphate shunt and G6PD
Aim

Answer 14

Glucose to glucose-6 phosphate
Requires G6PD
G6PD allows RBC membrane to be intact
loss = haemolysis under certain conditions
Aim = give NADPH for reduction reactions

Question 15

Glycogen Storage Disease
- inheritance
- example

Answer 15

A recessive
McArdle’s Disease

Question 16

Where is cholesterol absorbed?
What is needed to absorb cholesterol?

Answer 16

Small intestine
Bile acids

Question 17

How is cholesterol transported to the liver in the blood?

Answer 17

As chylomicrons/remnants

Question 18

What does the liver export cholesterol as?

Answer 18

VLDL

Question 19

What is VLDL transformed into?

Answer 19

IDL

Question 20

What is IDL transformed into?

Answer 20

LDL

Question 21

Where are the LDL receptors located?

Answer 21

Hepatic tissue
Adipose tissue

Question 22

What is lipogenesis?
Where does it occur?

Answer 22

= synthesis of triglycerides
Occurs in liver and adipose tissue

Question 23

How does fat into the duodenum trigger the release of bile acids?

Answer 23

Triggers release of cholecystokinin
= contraction of gallbladder and release of bile

Question 24

2Y causes of hypercholesterolaemia (5)

Answer 24

Hypothyroidism
Jaundice 2y to biliary obstruction
Nephrotic syndrome
Pregnancy
Diabetes

Question 25

Where does lipolysis occur? - organ - where in the cell - inhibited by

Answer 25

Liver and muscle Mitochondria Insulin

Question 26

Where does lipogenesis occur? - organ - where in the cell

Answer 26

Liver and adipose tissue Cytoplasm

Question 27

What is the main function/location of cholesterol?

Answer 27

Cell membrane

Question 28

What is involved in the metabolism of cholesterol?

Answer 28

HMG-CoA reductase

Question 29

What is the main dietary lipid?

Answer 29

Triglycerides

Question 30

Dietary fat > liver - what is the process?

Answer 30

Digested in small intestine, converted into chylomicrons, processed in liver, churned out as VLDL

Question 31

Where is glycogen stored (3)?

Answer 31

Liver Muscle Kidney

Question 32

Pathophysiology of DKA

Answer 32

Insulin deficiency = lack of available intracellular glucose Excessive lipolysis to produce ketones > acidosis

Question 33

Breakdown of fatty acids =

Answer 33

Acetyl coA Ketone bodies = can be used by all cells except brain in exceptional conditions

Question 34

Types of membrane receptors (4)

Answer 34

Ligand gated ion channels Voltage gated channels G protein coupled Tyrosine kinase receptors

Question 36

Where does the urea cycle occur?

Answer 36

Liver and brain e.g. cirrhosis - hepatic encephalopathy

Question 37

Pathophysiology of cystinuria - presentation - investigation

Answer 37

= defective amino acid transport Px: malabsorption, ataxia, pellagra Ix:cyanide nitroprusside test +VE

Question 38

Pathophysiology of homocystinuria - presentation - similar condition + difference

Answer 38

= collagen disorder Px: mental retardation, marfanoid, DOWNward lens dislocation Similar to Marfan's, in Marfan's the lens dislocation is UPward (because they are taller)

Question 39

What is Fanconi's Syndrome? - where does it effect? - presentation (4)

Answer 39

= renal tubular acidosis - proximal renal tubules - amino aciduria, hyperphosphataemia, hypokalaemia, osteomalacia

Question 40

B1 = Cause (2) Presentation (3)

Answer 40

= thiamine Chronic alcoholism, rice only diet Px: dry and wet beri beri, Wernicke's and Korsakoff syndrome

Question 41

B2 = Presentation (2)

Answer 41

= riboflavin Px: angular stomatitis, peripheral neuropathy

Question 42

B3 = Causes (2) Presentation Similarity

Answer 42

= niacin Chronic alcoholism, malabsorption Px: pellagra = diarrhoea, dementia, dermatitis Can see neurological symptoms similar to subacute combined degeneration of cord

Question 43

B6 = Causes (3) Presentation

Answer 43

= pyridoxine Alcoholics, pregnancy, isoniazid Px: peripheral neuropathy

Question 44

Cholecalciferol > 25 hydroxycholecalciferol - where does this occur?

Answer 44

Liver

Question 45

Presentation of hypomagnesiaemia (2)

Answer 45

Tetany Cardiac arrhythmia

Question 46

Where is iron absorbed? What happens there? How is it carried in plasma?

Answer 46

Small intestine Converted to ferritin Carried in plasma as Fe3+ bound to transferrin

Question 47

Methahaemoglobinaemia - problem - causes (4)

Answer 47

= iron is oxidised to Fe3+ so cannot carry O2 in Hb Causes = haemoglobinopathies. quinine, sulphonamides (co-trimoxazole), nitrates

Question 48

How is CO2 carried?

Answer 48

Most - bound as bicarbonate Some is free in the plasma