CM-UY 3314 November 26, 2024
Name: Total__________/60
EXAM 3
IF YOU HAVE A PHONE OR NOTES ON YOU OR AT YOUR DESK DURING THE
EXAM YOU WILL RECEIVE AN AUTOMATIC ZERO FOR THIS EXAM.
1. The levels of the second messenger involved in vasodilation are increased by
and decreased by . (2 pts)
a) cGMP cyclase; guanylate phosphodiesterase
b) Guanylate phosphodiesterase; cGMP cyclase
c) guanylate cyclase; cGMP phosphodiesterase
d) cGMP phosphodiesterase; guanylate cyclase
2. Describe the difference between coenzymes and cofactors. (2 pts)
Cofactors are inorganic molecules or metal ions (1 pt), while coenzymes are organic
molecules (1 pt).
−0.5 pts if they say ions for cofactors, but don’t mention the word “inorganic”
3. When the regulatory subunit of PKA is bound to cAMP, . (2 pts)
a) it dissociates into monomers.
b) it cannot bind to catalytic subunit of PKA.
c) the regulatory subunit is phosphorylated.
d) it is part of a tetramer.
• 1 pt if they select B. B is a consequence of A, but A is the main effect.
4. The substrate and product of an enzymatic reaction have the same molecular formula.
Which type of reaction occurred? (2 pts)
a) Condensation
b) Hydrolysis
c) Reduction
d) Isomerization
5. Albuterol is an agonist (1 pt) resembling epinephrine (1 pt) both in structure and
function. (2 pts)
, CM-UY 3314 November 26, 2024
6. An enzyme undergoes a mutation that causes it to lose the ability to be regulated via
phosphorylation. The mutation most likely affects which residue(s)? (2 pts)
Tyr, Ser, or Thr
• They need 2 out of 3 of these answers (1 pt each)
7. Statins lower serum cholesterol in a direct and indirect manner. Describe both. (4 pts)
Statins directly lower serum cholesterol levels by inhibiting HMG-CoA
reductase, which catalyzes the production of mevalonate (1 pt). Mevalonate is a
precursor to cholesterol synthesis. Cholesterol synthesized in the cell gets exported
to the serum. By impeding cholesterol synthesis intracellularly, serum cholesterol
levels are also lowered (1 pt). When intracellular cholesterol levels are low, this
triggers the cell to synthesize more LDL receptors which are transported to the cell
membrane (1 pt). There, receptors can bind to cholesterol-containing proteins,
engulfing them into the cell, thereby indirectly lowering serum cholesterol levels (1
pt).
−0.5 pts if they don’t mention the enzyme name or get the name wrong
−0.5 pts if they don’t explain how more LDL receptors appear on the surface
8. When bound to GTP, GαS obtains a conformation that promotes interaction with
adenylate cyclase. (2 pts)
9. Why are albuterol’s effects localized to the respiratory tract and lungs? (2 pts)
Albuterol is a β-2 agonist, and β-2 receptors are predominantly found in the
respiratory tract and lungs.
10. The substrate binding pocket of is best at accommodating substrates with
small side chains. (2 pts)
a) elastase
b) enolase
c) chymotrypsin
d) trypsin
• This question was removed, as the slide containing this information was
accidently omitted from the slides posted on Brightspace.
2
Name: Total__________/60
EXAM 3
IF YOU HAVE A PHONE OR NOTES ON YOU OR AT YOUR DESK DURING THE
EXAM YOU WILL RECEIVE AN AUTOMATIC ZERO FOR THIS EXAM.
1. The levels of the second messenger involved in vasodilation are increased by
and decreased by . (2 pts)
a) cGMP cyclase; guanylate phosphodiesterase
b) Guanylate phosphodiesterase; cGMP cyclase
c) guanylate cyclase; cGMP phosphodiesterase
d) cGMP phosphodiesterase; guanylate cyclase
2. Describe the difference between coenzymes and cofactors. (2 pts)
Cofactors are inorganic molecules or metal ions (1 pt), while coenzymes are organic
molecules (1 pt).
−0.5 pts if they say ions for cofactors, but don’t mention the word “inorganic”
3. When the regulatory subunit of PKA is bound to cAMP, . (2 pts)
a) it dissociates into monomers.
b) it cannot bind to catalytic subunit of PKA.
c) the regulatory subunit is phosphorylated.
d) it is part of a tetramer.
• 1 pt if they select B. B is a consequence of A, but A is the main effect.
4. The substrate and product of an enzymatic reaction have the same molecular formula.
Which type of reaction occurred? (2 pts)
a) Condensation
b) Hydrolysis
c) Reduction
d) Isomerization
5. Albuterol is an agonist (1 pt) resembling epinephrine (1 pt) both in structure and
function. (2 pts)
, CM-UY 3314 November 26, 2024
6. An enzyme undergoes a mutation that causes it to lose the ability to be regulated via
phosphorylation. The mutation most likely affects which residue(s)? (2 pts)
Tyr, Ser, or Thr
• They need 2 out of 3 of these answers (1 pt each)
7. Statins lower serum cholesterol in a direct and indirect manner. Describe both. (4 pts)
Statins directly lower serum cholesterol levels by inhibiting HMG-CoA
reductase, which catalyzes the production of mevalonate (1 pt). Mevalonate is a
precursor to cholesterol synthesis. Cholesterol synthesized in the cell gets exported
to the serum. By impeding cholesterol synthesis intracellularly, serum cholesterol
levels are also lowered (1 pt). When intracellular cholesterol levels are low, this
triggers the cell to synthesize more LDL receptors which are transported to the cell
membrane (1 pt). There, receptors can bind to cholesterol-containing proteins,
engulfing them into the cell, thereby indirectly lowering serum cholesterol levels (1
pt).
−0.5 pts if they don’t mention the enzyme name or get the name wrong
−0.5 pts if they don’t explain how more LDL receptors appear on the surface
8. When bound to GTP, GαS obtains a conformation that promotes interaction with
adenylate cyclase. (2 pts)
9. Why are albuterol’s effects localized to the respiratory tract and lungs? (2 pts)
Albuterol is a β-2 agonist, and β-2 receptors are predominantly found in the
respiratory tract and lungs.
10. The substrate binding pocket of is best at accommodating substrates with
small side chains. (2 pts)
a) elastase
b) enolase
c) chymotrypsin
d) trypsin
• This question was removed, as the slide containing this information was
accidently omitted from the slides posted on Brightspace.
2
