Test 82    (biochemistry)
1. The following are true about calcium:
a. the extracellular calcium concentration is over 10,000
    times that of intracellular calcium concentration

b. over 90% of intracellular calcium is protein-bound

c. cytosolic calcium is increased by the action of 
    phospholipase C

d. the effects of calcium are mainly mediated by 

e. protein kinase C, an enzyme that phosphorylates
    proteins requires calcium for maximum activity.

2. True statements include:

a. activation of a membrane receptor casues an exchange 
    of GTP for GDP

b. protein kinase is inactivated by cAMP

c. G-proteins that are bound to GTP are inactive

d. the a-subunite of G protein activates adenylate cyclase

e. G-proteins are made up of three subunits.

3. Glucogenesis:

a. maintains blood glucose druing overnight fast

b. occurs in both liver and muscles

c. is stimulated by elevated levels of acetyl CoA

d. is inhibited by fructose 2,6-biphosphate

e. uses carbon skeletons of amino acid

4. The following are true about cholesterol:

a. cholesterol is the most abundant sterol found in
    human tissue

b. cholic acid is a precursor in the biosynthesis of 

c. all the carbon atoms of cholesterol are derived 
    from acetyl CoA

d. HMG Co A reductase is the main regulator enzyme 
    of cholesterol synthesis

e. it is essential for the production of thyroxine

5. The following are true about blood glucose

a. muscle glycogen can not give rise to free 
    glucose because it lacks glucose 6-phospahte

b. liver glycogen is depleted after 12 hours of fasting

c. acetoacetate is an important source of carbon for
    glucose synthesis

d. lactate dervied from red blood cells is an important
    source of carbon for glucose synthesis.

e. after 48-hour of fasting, amino acid from the 
    breakdown of muscle protein is an important source
    of carbon for gllucose synthesis.

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