Download CHM 365 Name: Exam 3 Do all of the following 21 questions

CHM 365
Exam 3
Name:
Do all of the following 21 questions.
Multiple Choice: Circle the single, best answer.
1.
The lipid shown on the right represents what class of lipids?
a) Sphingolipid
b) Ceramide
c) Glycerophospholipid
d) Cholesterol
e) none of the above
2.
Membranes with unsaturated fatty acids in their components are more flexible and fluid because:
a) unsaturated fatty acids pack closely together to form ordered arrays.
b) unsaturated fatty acids bend at the double bond (cis) preventing close packing.
c) saturated fatty acids have a "kink" that produces more fluid aggregates.
d) unsaturated fatty acids have cis double bonds that prevent formation of stable bilayers
e) all of the above are correct
3.
Active transport is uniquely characterized by:
a) transport of hydrophobic molecules.
b) transport of hydrophilic molecules.
c) transport of a molecule or ion across a membrane, with the species going from a greater concentration
to a lesser concentration.
d) the linkage of an input of energy to drive a thermodynamically unfavorable reaction.
e) absolute requirement for ATP hydrolysis, no other energy source will work.
4.
The reaction of malate oxidation to oxaloacetate is not thermodynamically favored under standard
conditions. It occurs because:
a) it involves substrate- level phosphorylation.
b) it is coupled with a strong reduction.
c) it is coupled with ATP hydrolysis.
d) oxaloacetate is used in the next reaction which has a negative ∆G.
e) the previous reaction has a large negative ∆G.
5.
How many NADH molecules are produced in the TCA cycle per molecule of acetyl-CoA oxidized?
a) 1
6.
b) 2
c) 3
d) 4
e) 5
What is the effect of adding oligomyosin and then 2,4-dinitrophenol to respiring mitochondria?
a) Electron transport speeds up and ATP synthesis stops
b) Electron transport continues and ATP synthesis continues
c) Electron transport stops and ATP synthesis stops
d) Nothing, the uncoupler and inhibitor cancel each other out
e) Electron transport stops and ATP synthesis continues
7.
A characteristic of the glycerol phosphate shuttle is:
a) it shuttles NADH across the mitochondrial membrane to yield 3 ATP/NADH.
b) it shuttles "NADH electron equivalents" across the mitochondrial membrane to yield 2 ATP/NADH.
c) it only operates efficiently when the [NADH] in the cytoplasm is higher than in the matrix.
d) malate is a key component in the shuttle process.
e) aspartate is a key component in the shuttle process.
8.
Which of the following enzymes in the TCA cycle requires NAD+ as a cofactor?
a) fumarase
b) hexokinase
c) isocitrate dehydrogenase
d) aconitase
e) citrate synthase
Short Answer:
9.
Circle all of the following that are true about integral membrane proteins (intrinsic proteins):
a) have hydrophobic surfaces as well as hydrophilic surfaces.
b) dissociate from the membrane by treatment with salt solutions.
c) get exposed to one or both aqueous surfaces of the membrane.
d) insert into the membrane.
e) always extend all the way across the membrane.
10.
Circle all of the following that are true about peripheral proteins:
a) Can be easily released from the membrane by treatment with salt solutions.
b) Their removal from the membrane does not disrupt the entire membrane.
c) They can be noncovalently attached to the membrane
d) They can be covalently attached to the membrane
e) All peripheral proteins are attached to integral proteins
11.
Circle allof the following that are correct statements about the reaction catalyzed by citrate synthase:
a) Citrate synthase is allosterically activated by ATP.
b) The complete chemical equation is:
Oxaloacetate + acetyl-CoA + H2O → citrate + CoA
c) the reaction has a large positive ∆G value
d) The mechanism involves attack of the carbanion of acetyl-CoA on the carbonyl carbon of oxaloacetate.
e) The enzyme uses general base catalysis to generate the reactive species.
12.
Circle all of the following that are true about membranes:
a) Because of transverse (flip-flop) movement, the lipid compositions of the two layers of the membrane
equilibrate
b) An increase in the cholesterol content of the membrane decreases the fluidity of the membrane
c) All membranes contain 50% lipids and 50% proteins
d) Membranes are fluid
e) Membranes are asymmetric
13.
Circle all of the following that are true about membrane channels:
a)
b)
c)
d)
e)
Have a large aqueous area in the protein structure so are not very selective.
Can be opened or closed as a result of a change in the transmembrane potential.
Are an example of an integral protein in a membrane.
Commonly contain hydrophobic α helices.
Allow substrates to flow only from higher to lower concentrations.
14.
Why must citrate be oxidized to isocitrate in the second step of the TCA cycle (Explain why this is
necessary in a sentence or two)?
15.
The first step in the TCA cycle which converts oxaloacetate and acetyl-CoA to citrate is catalyzed by
citrate synthase which is an example of a ligase enzyme. All ligase enzymes require energy, so what
supplies the energy for this reaction? (answer in a sentence or two).
16.
For the TCA cycle, supply the missing substrate, enzyme, or product for the following reactions. Draw
the structure in (b).
a)
b)
17.
Describe how each of the following affect the electron transport system:
a) rotenone
b) cyanide
Calculations:
18.
Consider a phospholipid vesicle containing 10 mM galactose. The vesicle is bathed in a solution that
contains 50 mM galactose. What is the free energy at 37°C associated with moving a mole of galactose
molecules from outside the vesicle to the inside? (R=8.314 J/mole-K)
19.
What is the equilibrium constant (K eq) for the reduction of coenzyme Q by NADH as carried out by
complex I (NADH-coenzyme Q reductase) of the electron transport system?
NAD+ + 2H+ + 2e- → NADH + H+
E°= -0.32V
CoQ + 2H+ + 2e → CoQH2
E°= 0.060V
Essay:
20.
Explain how the electron transport system is linked to the production of ATP (oxidative
phosphorylation).
21.
Mammals in the arctic have higher levels of unsaturated fatty acids in their legs and hooves than in the
rest of their bodies. Suggest a reason for this phenomenon
Answers:
4. D
5. C
6. A
7. B
8. C
11. B,D
19. at 37°C, Keq= 2.3x1012