BCH 400/600
Spring 2002
Exam 3
March 25
Name_________________________
For Questions 1 thru 25, mark the correct answer on the Scantron answer sheet and the exam.
There will be only one correct answer for each question.
Multiple Choice (2 points each)
1) Which of the following is an acyl-lipid?
a. ubiquinone
b. chlorophyll
c. phosphatidylcholine
d. steroids
e. none of the above
2) Which of the following is not a property a lipid?
a. primarily non-polar compounds
b. highly soluble in non-polar organic solvents
c. amphipathic molecules
d. highly soluble in water
e. None of the above
3) A fatty acid designated 20:115 has a double bond located________________________.
a. between carbons 14 and 15 of the fatty acid counting from the carboxyl group.
b. between carbons 15 and 16 of the fatty acid counting from the carboxyl
group.
c. between carbons 14 and 15 of the fatty acid counting from the last methyl group.
d. between carbons 15 and 16 of the fatty acid counting from the last methyl group.
e. None of the above
4) Within a membrane bilayer, lipids and membrane associated proteins ______________.
a. can freely diffuse across the lipid bilayer.
b. freely exchange with aqueous cell fractions.
c. are fixed in position.
d. have free lateral movement.
e. None of the above
5) Which of the following types of membrane transporters do not show saturable kinetics?
a. passive (facilitative) transporters
b. active transporters
c. pores/channels
d. a and b
e. a and c
6) Factors influencing the phase transition temperature of a lipid bilayer are _______.
a. the length of the fatty acids attached to the phospholipids.
b. the number of double bonds in the fatty acids attached to the phospholipids.
c. the amount of cholesterol present.
d. All of the above.
e. None of the above.
7) Which of the following are factors related to the high yield of energy derived from the
cleavage of the phosphoanhydride linkages of ATP?
a. electrostatic repulsions between negatively charged oxygens.
b. entropy effects.
c. increased resonance stability of the products.
d. a high phosphoryl-group transfer potential.
e. All of the above.
8) The Go’hydrolysis for ATP to ADP and Pi = -32 kJ/mole and the Go’hydrolysis for
phosphoenolpyruvate to pyruvate and Pi = -62 kJ/mole. Based on this information, ATP
will serve as a(n) __________ in a phosphoryl-transfer reaction with
phosphoenolpyruvate.
a. donor
b. acceptor
c. equal
d. none of the above
e. all of the above
9) In the steady state model of metabolism, where A B C D, _________________.
a. the concentration of B and C are at equilbrium.
b. the concentration of B and C is constant because the rate of its formation is
equal to the rate of their utilization.
c. the concentration of B and C are decreased because the rate of their formation is
less than the rate of their utilization.
d. the concentration of B and C are increased because the rate of their formation is
higher than the rate of their utilization.
e. None of the above.
10) Under physiological conditions, the G of a reaction_____________________________.
a. is always equal to Go’.
b. is always dependent on the actual concentration of reactants and products.
c. is always near equilibrium.
d. is always metabolically irreversible.
e. None of the above.
11) Glycolysis can be described as ____________________________________.
a. an anabolic process.
b. a catabolic process.
c. None of the above.
12) In a linear organized metabolic pathway_________________________.
a. the same set of enzymes are used to synthesize different pathway intermediates.
b. the pathway intermediates are recycled.
c. the product of one reaction serves as the substrate for the subsequent
reaction.
d. the regulation always occurs at the last step in the pathway.
e. None of the above.
13) The Pasteur Effect refers to the observation that within the same organism rates of
glycolysis are ___________ under anaerobic conditions than under aerobic conditions.
a. lower
b. higher
c. the same
d. none of the above
14) Under anaerobic conditions pyruvate can be converted to
a. acetyl-CoA.
b. lactate.
c. ethanol.
d. a and b
e. b and c
15) Lactate dehydrogenase recycles NADH back to NAD+ to provide an oxidizing agent for
the glycolytic step catalyzed by which enzyme?
a. hexokinase
b. phosphoglycerate mutase
c. glyceraldehyde 3-phosphate dehydrogenase
d. triose phosphate isomerase.
e. phosphofructokinase.
16) In the reaction catalyzed by pyruvate dehydrogenase what coenzyme transfers the 2
carbon unit from the E1 subunit to Coenzyme A?
a. thiamin pyrophosphate
b. NAD+
c.
FAD+
d. Dihydrolipoamide
e. None of the above.
17) A symport transports ___________________.
a. a single molecule across a membrane.
b. two molecules in the same direction across a membrane.
c. two molecules in the opposite directions across a membrane.
d. None of the above.
18) The purpose of the Cori Cycle is to_______________________.
a. regenerate glucose in the liver from ethanol produced in the muscle tissues under
anaerobic conditions.
b. regenerate glucose in the liver from lactic acid produced in the muscle tissues
under anaerobic conditions.
c. regenerate lactic acid in the liver from ethanol produced in the muscle tissues
under anaerobic conditions.
d. regenerate glucose in the liver from galactose produced in the muscle tissues
under anaerobic conditions.
e. None of the above
19) Lactose intolerance is___________________________________________.
a. rarely observed in young children.
b. a normal developmental change in metabolism.
c. rarely observed in people of Northern European descent.
d. causes discomfort due to gas and diarrhea.
e. All of the above.
20) Tay Sach Disease and Niemann-Pick Diesease are inherited metabolic disorders related
to____________.
a. the inability to break down galactose.
b. the inability to digest lactose.
c. the inability to degrade sphingolipids.
d. the inability to remember all of the steps in glycolysis
e. None of the above.
QUESTIONS (21 THRU 25) MATCH THE FUNCTION WITH THE ENZYME (2
POINTS EACH)
a.
b.
c.
d.
e.
Generates GTP
Donates electrons directly to electron transport chain
Converts pyruvate to acetyl-CoA
Catalyzes an oxidative decarboxylation (generates NADH and CO2)
Point at which acetyl-CoA enters citric acid (TCA) cycle
21) ____B___ Succinate dehydrogenase
22) _____A___ Succinyl-CoA synthase
23) ____D____ Isocitrate dehydrogenase
24) _____E___ Citrate synthase
25) _____C___ Pyruvate dehydrogenase
26) (10 points) Draw the structure of phosphatidylserine with a palmitic acid and a linolenic acid
attached to the glycerol backbone.
27) (10 points) Although the Citric Acid (TCA) Cycle was primarily introduced in lecture as a
catabolic pathway, this pathway is also involved in a number of anabolic processes. List three
classes of unrelated compounds (i.e if you list proteins and amino acids that counts as only one)
that are synthesized from TCA cycle intermediates and the corresponding TCA intermediate
from which they are derived. Briefly explain why anaplerotic reactions are important to the
TCA Cycle in relationship to these anabolic processes.
28) (20 points) The next page contains the structures of all of the intermediates of glycolysis
from glucose to pyruvate. You need to do the following:
A. Draw a unidirectional arrow () between the substrate and the product of all
irreversible reactions.
B. Draw a bidirectional arrow () between the substrate and the product of all
reversible reactions.
C. For each step that consumes ATP, designate it as follows:
ATP
ADP
Reactant
Product
Note: the arrow may be unidirectional or bi-directional for these reactions. You are
required to know which is correct.
D. For each step that generates ATP, designate it as follows:
ADP
Reactant
ATP
Product
Note: the arrow may be unidirectional or bi-directional for these reactions. You are
required to know which is correct.
E. For the 3 regulated enzymatic reactions of glycolysis, write the name of the
reaction substrate and the name of the reaction product next to the correct
structure.
F. For the 3 regulated enzymatic reactions of glycolysis, write the name of the
enzyme.
G. For the 3 regulated enzymatic reactions of glycolysis , list all allosteric activators
and allosteric inhibitors involved in the regulation of these reactions. You need to
make it clear what are the inhibitors and what are the activators.
Questions 29 thru 33. (2 points each) Match the specific component from the signal transduction
pathway above with its function below.
Adenyl
cylase
Epinephrine
receptor
cAMP
Protein Kinase A
(inactive)
Protein Kinase A
(active)
cellular response
29) ____Epinephrine__________ External stimulus (First messenger)
30) ______G-protein__________ Transducer
31) ______Adenylate cyclase
effector enzyme
32) _______cAMP__________________ Second messenger
33) ___________Protein Kinase A______________ Cytoplasmic effector enzyme.
EXTRA CREDIT (5 POINTS)
Describe how the Kcat (turnover number) of the G-protein GTPase activity relates to the duration
of the signaling response. Why would a G-protein with a higher Kcat or lower Kcat be
undesirable in a signaling pathway?
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