Download Bio302 Biochemistry II

Bio302 Biochemistry II
Second Midterm Examination, April 27, 2007
Multiple choice questions have one correct answer, each 4 points.
Question 1. (10 points) Fill in the blanks
a) The is another name for glycolysis:……………………..
b) This is the process by which noncarbohydrate precursor molecules are converted
into glucose:……………………..
c) This substance must be regenerated for glycolysis to proceed:………………….
d) This intermediate is necessary for the conversion of galactose to
glucose:…………
e) This molecule is an allosteric inhibitor of phosphofructokinase:………………
f) This essential nutrient is required for the carboxylation of pyruvate in humans:
g) This is an allosteric activator of glycolysis:……………………..
h) The key enzyme that regulates the pace of glycolysis is……………………….
i) The common structural domain of NAD binding dehydrogenases is often called
a………………………………………..after the scientist who first recognized it.
j) In alcoholic fermentation, the decarboxylation of pyruvate requires a coenzyme
that contains the vitamin………………………
Question 2. What is the purpose of phosphorylating glucose in cytosol?
a) to trap glucose in the cell
b) to destabilize glucose and facilitate the next series of metabolic steps
c) to convert it to a more soluble form
d) all of the above
e) a and b
Question 3. What reaction is catalyzed by aldolase?
a) isomerization of DHAP to GAP
b) ligation of GAP and DHAP
c) reversible cleavage of F-1,6-BP to DHAP and GAP
d) cleavage of DHAP to GAP
e) irreversible aldol condensation of DHAP and GAP
Quastion 4. How are the glycolytic enzymes regulated?
a) transcriptional control
b) reversible phosphorylation
c) allosteric control
d) all of the above
e) none of the above
Question 5. (5 points) Why is it more sensible for phosphofructokinase to be an important
control step rather than hexokinase?
Question 6. (5 points) How are gluconeogenesis and glycolysis regulated reciprocally?
Question 7. (5 points) What is a substrate cycle. What two functions are attributed to
substrate cycles?
Question 8. Which of the following vitamins are precursors to cofactors necessary for the
formation of acetyl CoA?
a) thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid
b) thiamine, riboflavin, niacin, lipoic acid, pantothenic acid, and biotin
c) thiamine, ribobflavin, niacin, and biotin
d) thiamine, riboflavin, and lipoic acid
e) none of the above
Question 9. Formation of citrate is a(n) ……………………………..reaction.
a) oxidation
b) reduction
c) condensation
d) ligation
e) hydrolysis
Question 10. (5 points) Fill in the blanks
a) The location of succinate dhydrogenase is………………………
b) This substance is toxic, because it reacts qith the neighboring sulfhydry groups of
dihydrolipoyl groups and blocks its reoxidation to lipoamide:…………………..
c) This is the name applied to metabolic reactions that replenish citric acid cycle
intermediates that are depleted because they were used for
biosynthesis:………………..
d) These proteins are tightly associated with FAD or FMN:……………..
e) This is the site at which citric acid reactions takes place.:………………………..
Question 11. Which of the following functions as a “flexible swinging arm* when it
transfers the reaction intermediate from one active site to the next?
a) FAD
b) NAD+
c) Lipoamide
d) Thiamine pyrophosphate
e) Coenzyme
Question 12. Which of the following conditions will activate pyruvate dehydrogenase
kinase which catalyzes the phosphorylation and inactivation of E1 in the pyruvate
dehydrogenase complex?
a) elevated concentrations of NADTH and ATP
b) elevated concentrations of NAD+ and ADP
c) Ca++
d) Insulin
e) Elevated concentrations of acetyl-CoA
Question 13. (5 points) Explain why a GTP is energetically equivalent to an ATP in
metabolism.
Question 14. (5 points) What is the energy source that drives the condensation of
oxaloacetate and acetylCoA to produce citrate by citrate synthase? Explain.
Question 15. (5 points) Fill in the blanks.
a) This electron carrier is a derivative of quinone and has an isoprenoid
tail:………………….
b) This enzyme catalyzes the reduction of oxygen:………………….
c) A strong oxidizing agent has a strong tendency
to…………………..(accept/donate) electron(s).
d) The transfer of a single electron to O2 forms the
reactive………………………ion.
e) Cytocrome…………….is the only water soluble cytochrome of the electron
transport chain.
Question 16. In prokaryotes the site of ATP synthesizing machinery is
a) the mitochondrial matrix
b) the outer cell wall
c) the cytoplasmic membrane
d) the nucleolus
e) none of the above
Question 17. Which of the following does not pump protons?
a) Complex I
b) Complex II
c) Complex III
d) Complex IV
e) All o the above
Question 18. In the Rieske center, the iron sulfur center is coordinated to the amino acids
a) His
b) Cys
c) His and Cys
d) Cys and Met
e) None of them
Question 19. (5 points) Explain why less ATP is made from the reoxidation of FADH2 as
compared to NADH.
Question 20. (5 points) What is the actual function of the protons in the synthesis of ATP
by FoF1 ATP synthase?
Question 21. How is light used in photosynthesis?
a) The light is necessary to make the chlorophyll green, so the pigment can transmit
electrons.
b) The light is used to generate high energy electrons with great reducing potential
c) The light provides heat energy for the chloroplasts.
d) The light is absorbed by oxygen which is converted into water
e) None of the above
Question 22. (5 points)Why are chlorophylls good candidates or photoreceptors?