past paper questions

Question 1

1. A 65 year old man is diagnosed with bladder cancer. Analysis of DNA from the tumour cells shows a mutation in the ras GTPase oncogene. This mutation locks the Ras protein into a state where it permanently binds GTP.

What effect does this have on the Ras protein?

A.	It is inactivated
B.	It is constitutively activated
C.	It is degraded
D.	It is dephosphorylated 
E.	It translocates to the nucleus

Answer 1

B

Question 2

1. Parkinson’s disease is a neurological condition, characterised by hypokinesia (diminished motor function), tremor and muscular rigidity.

L-DOPA is used to treat this disease because?

A. Dopamine does not cross the blood-brain barrier
B. L-DOPA evokes dopamine release
C. L-DOPA selectively antagonises enzymes which inactivate dopamine
D. The chemical synthesis of dopamine is uneconomic
E. The effects of L-DOPA are longer lasting than those of dopamine

Answer 2

A

Question 3

1. You are working for a pharmaceutical company. You are screening a batch of novel G protein-coupled receptor agonists and note that one compound, PCMD101, is labelled as Gαq specific?

Measuring the production of which of the following would enable you to estimate the activity of this compound?

A.	ATP
B.	Cyclic AMP
C. 	Intracellular adenosine
D.	Intracellular Ca2+
E.	Tyrosine kinase

Answer 3

D

Question 4

1. A fit and healthy 21 year old male Medical Science student with normal kidneys decreases his intake of dietary sodium by half over a period of two months.

Which of the following would be expected to be increased in response to this restriction of dietary sodium?

A.	Arterial pressure
B.	Extracellular fluid volume
C.	Release of Atrial Natriuretic Peptide (ANP) 
D.	Release of renin
E.	Sodium excretion

Answer 4

D

Question 5

1. A 25 year old man suffers from a stab wound in the abdomen, requiring a removal of 150 cm of terminal ileum. Two years after the surgery, he complains of increasing malaise and watery diarrhoea. He reports eating a normal and unrestricted diet. A diagnosis of anaemia is made.
   What is the most likely cause of his anaemia?

A.	Folate malabsorption
B.	Impaired secretion of intrinsic factor (IF)
C.	Iron deficiency
D.	Malabsorption of IF-B12 complex
E.	Pancreatic insufficiency

Answer 5

D

Question 6

1. in 1997 Jen Skou won half of the Nobel Prize for Chemistry for his discovery of the Na+/K+ ATPase enzyme. This enzyme uses ATP to transport sodium and potassium ions against their concentration gradients.
   What contribution does it make to the resting membrane potential of neurons?
   A. Too small to measure
   B. Depolarisation by a few millivolts
   C. Hyperpolarisation by a few millivolts
   D. Depolarisation by tens of millivolts
   E. Hyperpolarisation by tens of millivolts

Answer 6

C

Question 7

1. Many ion channels involved in the generation of action potentials are voltage-gated; their opening allows ions to cross the membrane and drives the membrane potential towards that ion’s equilibrium potential.
   During an action potential in a typical neuron, which potential would see the most sodium ions crossing the membrane?
   A. -80 mV
   B. -60 mV
   C. -15 mV
   D. 60 mV
   E. 150 mV

Answer 7

c

Question 8

1. Protein kinase A (PKA) activation occurs downstream of G-protein coupled receptor signalling mediated by Gαs. You are working for a pharmaceutical company that would like to inhibit this pathway and must decide on a suitable target.

Which target would be a good candidate for an inhibitor?

A.	Adenylate cyclase
B.	cAMP phosphodiesterase
C.	C-Src
D.	EGF receptor
E.	MAP kinase

Answer 8

A

Question 9

1. A woman takes her 16 year old son to visit the GP because he is much smaller than the other boys in his class, even though she and her husband are above average height. He also has no body hair and his voice hasn’t broken yet. A blood tests shows he has low follicle stimulating hormone levels.

The stimulation of which process is the primary physiological effect of the hormone in this case?

A. Development of secondary sexual characteristics
B. Follicle development
C. Growth of the long bones
D. Pulsatile release of gonadotrophin releasing hormone
E. Spermatogenesis

Answer 9

E

Question 10

1. A 42 year old man is prescribed a statin because of high serum cholesterol.

What is the principle mechanism by which this class of drug reduces serum cholesterol?

A. Down-regulation of hepatic LDL receptors
B. Opsonising cholesterol for macrophage phagocytosis
C. Reduction in hepatic mevalonate production
D. Suppression of dietary cholesterol absorption
E. Up-regulation of vascular HDL receptors

Answer 10

c

Question 11

1. During your neuroanatomy class you are exploring a sheep’s brain. Your partner reminds you that the meninges form a protective barrier around the brain and can be classified into three layers.

What is the innermost protective layer?

A.	Arachnoid membrane
B.	Arachnoid trabecula
C.	Cerebrospinal layer
D.	Dura mater
E.	Pia mater

Answer 11

e

Question 12

Which one of the following blood vessels has the highest compliance?

Answer 12

VEINS

Question 13

a decrease in arteriole diameter would most likely resultt in

Answer 13

decrease in intersisital hydrostatic pressure, capillary hydrostatic pressure and lymph flow