Bio102 Problems
Aerobic Respiration
1. Since prokaryotes have no mitochondrial membranes, electron transport
A. cannot happen.
B. is bypassed.
C. happens in the peroxisome.
D. occurs in the cytosol.
E. happens on the cell membrane.
2. Which process produces ATP by substrate-level phosphorylation?
A. Electron Transport
B. Citric Acid Cycle
C. Chemiosmosis
D. Transition Step
E. Light-Dependent Reactions
3. If a carbon atom has become reduced, it
A. has fewer bonds to oxygen.
B. has a lower electron density near its nucleus.
C. has fewer bonds to carbon or hydrogen.
D. is released as CO2.
E. is covalently attached to a co-enzyme.
4. How many carbon atoms are present in one molecule of Acetyl-CoA?
A. 1
B. 2
C. 3
D. 4
E. 0
5. Food molecules that are more reduced contain more usable energy because they
A. can be used to reduce more coenzymes.
B. move more easily through membranes.
C. contain more phosphate to be transferred to ADP molecules.
D. can be consumed more rapidly by anaerobic metabolism.
E. directly enter oxidative phosphorylation.
6. Why does the oxidation of one molecule of FADH2 yield less usable energy than oxidation of one
molecule of NADH?
When re-oxidized, the electrons from FADH2 enter the electron transport chain in Complex II.
The electrons from NADH enter the electron transport chain in Complex I. Complex I pumps
protons across the mito inner membrane, but Complex II does not. The moved protons are
eventually used to synthesize ATP.
7. Formic acid, which contains a single carbon atom, is shown below. In the corresponding boxes,
draw the structure of a different molecule which is one step more oxidized than formic acid and
then another that is one step more reduced than formic acid.
Formic Acid
One step more oxidized
One step more reduced
O
O

H-C-OH

CO2
H-C-H
8. In aerobic metabolism, what process (or processes) produces CO2?
Transitions Step, Citric Acid Cycle
9. For the electron transport chain used in aerobic metabolism,
the initial electron donor is __NADH/FADH2______,
the final electron acceptor is __O2______________,
and the electron has gained/lost energy during transport.
10. When protons are moved across the mitochondrial inner membrane in the electron transport chain,
this is one type of
A. facilitated transport.
B. simple diffusion.
C. active transport.
D. pinocytosis.
E. exocytosis.
11. Circle the letter of the molecule whose carbon atom has the most usable cellular energy.
A. CO2
B. CH3OH
C. CH4
D. HCOH
||
O
12. In our discussions of oxidative phosphorylation, we mainly discussed the mitochondrial inner
membrane. Prokaryotes can also carry out electron transport and oxidative phosphorylation, but
prokaryotes have no mitochondria. How does oxidative phosphorylation in prokaryotes happen
without a mitochondrial membrane?
The plasma membrane is used instead.
13. The structure of acetaldehyde is shown below. This can be a substrate for two different enzymes
that use two different coenzymes, as shown. For each oxidation/reduction reaction, draw the
structure of a possible product.
A.
and NADPH
B.
and FAD
and NADP+
CH3-CH2OH
CH3-COOH
and FADH2
14. Cyanide is poisonous to people because it blocks oxidative phosphorylation by directly binding to one of
the essential proteins. Why does treating cells with cyanide also cause the Transition Step to quickly stop?
Without oxidative phosphorylation, the coenzymes NADH and FADH2 can’t become
reoxidized. In the absence of NAD+ and FAD, the citric acid cycle stops working since those
are essential substrates.
15. How many carbon atoms are in each of the following molecules?
AcCoA ___2_____
Glucose ___6_____
Pyruvate ___3_____
16. Are each of the following reactions an oxidation reaction, a reduction reaction, both or neither?
NADP+ → NADPH
Oxidation
Reduction
Both
Neither
ADP + PO4 → ATP
Oxidation
Reduction
Both
Neither
Oxidation
Reduction
Both
Neither
17. We can isolate mitochondria from liver cells and measure the rate at which electron transport
proceeds as well as their ability to make ATP. Then we can modify their phospholipids and
observe the following effects:
17A. If we modify the phospholipids in the mitochondria so that they are less unsaturated, we find
the rate at which electron transport proceeds decreases substantially as does the amount of ATP
synthesized. Please briefly explain why less unsaturated phospholipids cause these effects.
Less unsaturated phospholipids decreases the fluidity and permeability of the membrane. It’s likely
that the fluidity fell so much that the complexes can’t move around well and thus can’t transfer
elelctrons efficiently.
17B. Alternatively, if we modify the phospholipids in the mitochondria so that they are more
unsaturated, we find that electron transport proceeds well, but very little ATP is made. Please
briefly explain why more unsaturated phospholipids cause these effects.
Less-saturated phospholipids makes the membrane more fluid and also more permeable. It’s likely
that it is now so permeable that the protons can diffuse across the inner membrane without
passing through ATP synthase.
17C. Based on the above data, what do you think would happen to the rate of electron transport and
the amount of ATP made if we added cholesterol to the membrane? Why?
This should make the membrane less fluid and less permeable, so it should mimic the outcome of
part 17A: decreased electron transport and decreased ATP synthesis
18. The following reaction requires a coenzyme. Is NAD+ or NADH the second substrate? Briefly
explain how you arrived at your answer.
Substrate: NAD+
or
NADH
The middle carbon on the substrate molecule is getting oxidized (going from one bond to oxygen to
two bonds to oxygen). Thus, the coeznyme must be getting reduced, so we need to start with the
oxidized form of the coenzyme.