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What fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle, if glucose is the sole energy source?
What fraction of the carbon dioxide exhaled by animals is generated by the reactions of the citric acid cycle, if glucose is the sole energy source?
A) 1/6
B) 1/3
C) 1/2
D) 2/3
E) 100/100
Answer: D
Where are the proteins of the electron transport chain
located?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix
Answer: C
In cellular respiration, the energy for most ATP
synthesis is supplied by
A) high energy phosphate bonds in organic molecules.
B) a proton gradient across a membrane.
C) converting oxygen to ATP.
D) transferring electrons from organic molecules to
pyruvate.
E) generating carbon dioxide and oxygen in the electron
transport chain.
Answer: B
During aerobic respiration, which of the following
directly donates electrons to the electron transport chain at the lowest energy
level?
A) NAD+
B) NADH
C) ATP
D) ADP + Pi
E) FADH2
Answer: E
The primary role of oxygen in cellular respiration is to
A) yield energy in the form of ATP as it is passed down
the respiratory chain.
B) act as an acceptor for electrons and hydrogen, forming
water.
C) combine with carbon, forming CO₂.
D) combine with lactate, forming pyruvate.
E) catalyze the reactions of glycolysis.
Answer: B
Inside an active mitochondrion, most electrons follow
which pathway?
A) glycolysis → NADH → oxidative phosphorylation → ATP →
oxygen
B) citric acid cycle → FADH₂ → electron transport chain →
ATP
C) electron transport chain → citric acid cycle → ATP →
oxygen
D) pyruvate → citric acid cycle → ATP → NADH → oxygen
E) citric acid cycle → NADH → electron transport chain →
oxygen
Answer: E
During aerobic respiration, H₂O is formed. Where does the
oxygen atom for the formation of the water come from?
A) carbon dioxide (CO₂)
B) glucose (C₆H₁₂O₆)
C) molecular oxygen (O₂)
D) pyruvate (C₃H₃O₃-)
E) lactate (C₃H₅O₃-)
Answer: C
In chemiosmotic phosphorylation, what is the most direct
source of energy that is used to convert ADP + Pi to ATP?
A) energy released as electrons flow through the electron
transport system
B) energy released from substrate-level phosphorylation
C) energy released from movement of protons through ATP
synthase, against the electrochemical gradient
D) energy released from movement of protons through ATP
synthase, down the electrochemical gradient
E) No external source of energy is required because the
reaction is exergonic.
Answer: D
Energy released by the electron transport chain is used
to pump H⁺ into which location in eukaryotic cells?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix
Answer: D
The direct energy source that drives ATP synthesis during
respiratory oxidative phosphorylation in eukaryotic cells is
A) oxidation of glucose to CO₂ and water.
B) the thermodynamically favorable flow of electrons from
NADH to the mitochondrial electron transport carriers.
C) the final transfer of electrons to oxygen.
D) the proton-motive force across the inner mitochondrial
membrane.
E) the thermodynamically favorable transfer of phosphate
from glycolysis and the citric acid cycle intermediate molecules of ADP.
Answer: D
When hydrogen ions are pumped from the mitochondrial
matrix across the inner membrane and into the intermembrane space, the result
is the
A) formation of ATP.
B) reduction of NAD⁺.
C) restoration of the Na⁺/K⁺ balance across the membrane.
D) creation of a proton-motive force.
E) lowering of pH in the mitochondrial matrix.
Answer: D
Where is ATP synthase located in the mitochondrion?
A) cytosol
B) electron transport chain
C) outer membrane
D) inner membrane
E) mitochondrial matrix
Answer: D
It is possible to prepare vesicles from portions of the
inner mitochondrial membrane. Which one of the following processes could still
be carried on by this isolated inner membrane?
A) the citric acid cycle
B) oxidative phosphorylation
C) glycolysis and fermentation
D) reduction of NAD⁺
E) both the citric acid cycle and oxidative
phosphorylation
Answer: B
How many oxygen molecules (O₂) are required each time a
molecule of glucose (C₆H₁₂O₆) is completely oxidized to carbon dioxide and
water via aerobic respiration,?
A) 1
B) 3
C) 6
D) 12
E) 30
Answer: C
Which of the following produces the most ATP when glucose
(C₆H₁₂O₆) is completely oxidized to carbon dioxide (CO₂) and water?
A) glycolysis
B) fermentation
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle
E) oxidative phosphorylation (chemiosmosis)
Answer: E
Approximately how many molecules of ATP are produced from
the complete oxidation of two molecules of glucose (C₆H₁₂O₆) in aerobic
cellular respiration?
A) 2
B) 4
C) 15
D) 30-32
E) 60-64
Answer: E
The synthesis of ATP by oxidative phosphorylation, using
the energy released by movement of protons across the membrane down their
electrochemical gradient, is an example of
A) active transport.
B) an endergonic reaction coupled to an exergonic
reaction.
C) a reaction with a positive ΔG .
D) osmosis.
E) allosteric regulation.
Answer: B
Chemiosmotic ATP synthesis (oxidative phosphorylation)
occurs in
A) all cells, but only in the presence of oxygen.
B) only eukaryotic cells, in the presence of oxygen.
C) only in mitochondria, using either oxygen or other
electron acceptors.
D) all respiring cells, both prokaryotic and eukaryotic,
using either oxygen or other electron acceptors.
E) all cells, in the absence of respiration.
Answer: D
If a cell is able to synthesize 30 ATP molecules for each
molecule of glucose completely oxidized by carbon dioxide and water, how many
ATP molecules can the cell synthesize for each molecule of pyruvate oxidized to
carbon dioxide and water?
A) 0
B) 1
C) 12
D) 14
E) 15
Answer: C
What is proton-motive force?
A) the force required to remove an electron from hydrogen
B) the force exerted on a proton by a transmembrane
proton concentration gradient
C) the force that moves hydrogen into the intermembrane
space
D) the force that moves hydrogen into the mitochondrion
E) the force that moves hydrogen to NAD⁺
Answer: B
In liver cells, the inner mitochondrial membranes are
about five times the area of the outer mitochondrial membranes. What purpose
must this serve?
A) It allows for an increased rate of glycolysis.
B) It allows for an increased rate of the citric acid
cycle.
C) It increases the surface for oxidative
phosphorylation.
D) It increases the surface for substrate-level
phosphorylation.
E) It allows the liver cell to have fewer mitochondria.
Answer: C
Brown fat cells produce a protein called thermogenin in
their mitochondrial inner membrane. Thermogenin is a channel for facilitated transport
of protons across the membrane. What will occur in the brown fat cells when
they produce thermogenin?
A) ATP synthesis and heat generation will both increase.
B) ATP synthesis will increase, and heat generation will
decrease.
C) ATP synthesis will decrease, and heat generation will
increase.
D) ATP synthesis and heat generation will both decrease.
E) ATP synthesis and heat generation will stay the same.
Answer: C
In a mitochondrion, if the matrix ATP concentration is
high, and the intermembrane space proton concentration is too low to generate
sufficient proton-motive force, then
A) ATP synthase will increase the rate of ATP synthesis.
B) ATP synthase will stop working.
C) ATP synthase will hydrolyze ATP and pump protons into
the intermembrane space.
D) ATP synthase will hydrolyze ATP and pump protons into
the matrix.
Answer: C
Which catabolic processes may have been used by cells on
ancient Earth before free oxygen became available?
A) glycolysis and fermentation only
B) glycolysis and the citric acid cycle only
C) glycolysis, pyruvate oxidation, and the citric acid
cycle
D) oxidative phosphorylation only
E) glycolysis, pyruvate oxidation, the citric acid cycle,
and oxidative phosphorylation, using an electron acceptor other than oxygen
Answer: E
Which of the following normally occurs regardless of
whether or not oxygen (O₂) is present?
A) glycolysis
B) fermentation
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle
E) oxidative phosphorylation (chemiosmosis)
Answer: A
Which of the following occurs in the cytosol of a
eukaryotic cell?
A) glycolysis and fermentation
B) fermentation and chemiosmosis
C) oxidation of pyruvate to acetyl CoA
D) citric acid cycle
E) oxidative phosphorylation
Answer: A
Which metabolic pathway is common to both cellular
respiration and fermentation?
A) the oxidation of pyruvate to acetyl CoA
B) the citric acid cycle
C) oxidative phosphorylation
D) glycolysis
E) chemiosmosis
Answer: D
The ATP made during fermentation is generated by which of
the following?
A) the electron transport chain
B) substrate-level phosphorylation
C) chemiosmosis
D) oxidative phosphorylation
E) aerobic respiration
Answer: B
In the absence of oxygen, yeast cells can obtain energy
by fermentation, resulting in the production of
A) ATP, CO₂, and ethanol (ethyl alcohol).
B) ATP, CO₂, and lactate.
C) ATP, NADH, and pyruvate.
D) ATP, pyruvate, and oxygen.
E) ATP, pyruvate, and acetyl CoA.
Answer: A
