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What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
What is the term for metabolic pathways that release stored energy by breaking down complex molecules?
A) anabolic pathways
B) catabolic pathways
C) fermentation pathways
D) thermodynamic pathways
E) bioenergetic pathways
Answer: B
The molecule that functions as the reducing agent
(electron donor) in a redox or oxidation-reduction reaction
A) gains electrons and gains potential energy.
B) loses electrons and loses potential energy.
C) gains electrons and loses potential energy.
D) loses electrons and gains potential energy.
E) neither gains nor loses electrons, but gains or loses
potential energy.
Answer: B
When electrons move closer to a more electronegative
atom, what happens?
A) The more electronegative atom is reduced, and energy
is released.
B) The more electronegative atom is reduced, and energy
is consumed.
C) The more electronegative atom is oxidized, and energy
is consumed.
D) The more electronegative atom is oxidized, and energy
is released.
E) The more electronegative atom is reduced, and entropy
decreases.
Answer: A
Why does the oxidation of organic compounds by molecular
oxygen to produce CO₂ and water release free energy?
A) The covalent bonds in organic molecules and molecular
oxygen have more kinetic energy than the covalent bonds in water and carbon
dioxide.
B) Electrons are being moved from atoms that have a lower
affinity for electrons (such as C) to atoms with a higher affinity for
electrons (such as O).
C) The oxidation of organic compounds can be used to make
ATP.
D) The electrons have a higher potential energy when
associated with water and CO₂ than they do in organic compounds.
E) The covalent bond in O₂ is unstable and easily broken
by electrons from organic molecules.
Answer: B
Which of the following statements describes the results
of this reaction?
C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy
A) C₆H₁₂O₆ is oxidized and O₂ is reduced.
B) O₂ is oxidized and H₂O is reduced.
C) CO₂ is reduced and O₂ is oxidized.
D) C₆H₁₂O₆ is reduced and CO₂ is oxidized.
E) O₂ is reduced and CO₂ is oxidized.
Answer: A
When a glucose molecule loses a hydrogen atom as the
result of an oxidation-reduction reaction, the molecule becomes
A) hydrolyzed.
B) hydrogenated.
C) oxidized.
D) reduced.
E) an oxidizing agent.
Answer: C
When a molecule of NAD⁺ (nicotinamide adenine
dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes
A) dehydrogenated.
B) oxidized.
C) reduced.
D) redoxed.
E) hydrolyzed.
Answer: C
Which of the following statements describes NAD⁺?
A) NAD⁺ is reduced to NADH during glycolysis, pyruvate
oxidation, and the citric acid cycle.
B) NAD⁺ has more chemical energy than NADH.
C) NAD⁺ is oxidized by the action of hydrogenases.
D) NAD⁺ can donate electrons for use in oxidative
phosphorylation.
E) In the absence of NAD⁺, glycolysis can still function.
Answer: A
Where does glycolysis take place in eukaryotic cells?
A) mitochondrial matrix
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) cytosol
Answer: E
The ATP made during glycolysis is generated by
A) substrate-level phosphorylation.
B) electron transport.
C) photophosphorylation.
D) chemiosmosis.
E) oxidation of NADH to NAD⁺.
Answer: A
The oxygen consumed during cellular respiration is
involved directly in which process or event?
A) glycolysis
B) accepting electrons at the end of the electron
transport chain
C) the citric acid cycle
D) the oxidation of pyruvate to acetyl CoA
E) the phosphorylation of ADP to form ATP
Answer: B
Which process in eukaryotic cells will proceed normally
whether oxygen (O₂) is present or absent?
A) electron transport
B) glycolysis
C) the citric acid cycle
D) oxidative phosphorylation
E) chemiosmosis
Answer: B
An electron loses potential energy when it
A) shifts to a less electronegative atom.
B) shifts to a more electronegative atom.
C) increases its kinetic energy.
D) increases its activity as an oxidizing agent.
E) moves further away from the nucleus of the atom.
Answer: B
Why are carbohydrates and fats considered high energy
foods?
A) They have a lot of oxygen atoms.
B) They have no nitrogen in their makeup.
C) They can have very long carbon skeletons.
D) They have a lot of electrons associated with hydrogen.
E) They are easily reduced.
Answer: D
Substrate-level phosphorylation accounts for
approximately what percentage of the ATP formed by the reactions of glycolysis?
A) 0%
B) 2%
C) 10%
D) 38%
E) 100%
Answer: E
During glycolysis, when each molecule of glucose is
catabolized to two molecules of pyruvate, most of the potential energy
contained in glucose is
A) transferred to ADP, forming ATP.
B) transferred directly to ATP.
C) retained in the two pyruvates.
D) stored in the NADH produced.
E) used to phosphorylate fructose to form fructose
6-phosphate.
Answer: C
In addition to ATP, what are the end products of
glycolysis?
A) CO₂ and H₂O
B) CO₂ and pyruvate
C) NADH and pyruvate
D) CO₂ and NADH
E) H₂O, FADH₂, and citrate
Answer: C
The free energy for the oxidation of glucose to CO₂ and
water is -686 kcal/mol and the free energy for the reduction of NAD⁺ to NADH is
+53 kcal/mol. Why are only two molecules of NADH formed during glycolysis when
it appears that as many as a dozen could be formed?
A) Most of the free energy available from the oxidation
of glucose is used in the production of ATP in glycolysis.
B) Glycolysis is a very inefficient reaction, with much
of the energy of glucose released as heat.
C) Most of the free energy available from the oxidation
of glucose remains in pyruvate, one of the products of glycolysis.
D) There is no CO₂ or water produced as products of
glycolysis.
E) Glycolysis consists of many enzymatic reactions, each
of which extracts some energy from the glucose molecule.
Answer: C
Starting with one molecule of glucose, the
energy-containing products of glycolysis are
A) 2 NAD⁺, 2 pyruvate, and 2 ATP.
B) 2 NADH, 2 pyruvate, and 2 ATP.
C) 2 FADH₂, 2 pyruvate, and 4 ATP.
D) 6 CO₂, 2 ATP, and 2 pyruvate.
E) 6 CO₂, 30 ATP, and 2 pyruvate.
Answer: B
In glycolysis, for each molecule of glucose oxidized to
pyruvate
A) two molecules of ATP are used and two molecules of ATP
are produced.
B) two molecules of ATP are used and four molecules of
ATP are produced.
C) four molecules of ATP are used and two molecules of
ATP are produced.
D) two molecules of ATP are used and six molecules of ATP
are produced.
E) six molecules of ATP are used and six molecules of ATP
are produced.
Answer: B
A molecule that is phosphorylated
A) has been reduced as a result of a redox reaction
involving the loss of an inorganic phosphate.
B) has a decreased chemical reactivity; it is less likely
to provide energy for cellular work.
C) has been oxidized as a result of a redox reaction
involving the gain of an inorganic phosphate.
D) has an increased chemical potential energy; it is
primed to do cellular work.
E) has less energy than before its phosphorylation and
therefore less energy for cellular work.
Answer: D
Which kind of metabolic poison would most directly
interfere with glycolysis?
A) an agent that reacts with oxygen and depletes its
concentration in the cell
B) an agent that binds to pyruvate and inactivates it
C) an agent that closely mimics the structure of glucose
but is not metabolized
D) an agent that reacts with NADH and oxidizes it to NAD⁺
E) an agent that blocks the passage of electrons along
the electron transport chain
Answer: C
Why is glycolysis described as having an investment phase
and a payoff phase?
A) It both splits molecules and assembles molecules.
B) It attaches and detaches phosphate groups.
C) It uses glucose and generates pyruvate.
D) It shifts molecules from cytosol to mitochondrion.
E) It uses stored ATP and then forms a net increase in
ATP.
Answer: E
The transport of pyruvate into mitochondria depends on
the proton-motive force across the inner mitochondrial membrane. How does
pyruvate enter the mitochondrion?
A) active transport
B) diffusion
C) facilitated diffusion
D) through a channel
E) through a pore
Answer: A
Which of the following intermediary metabolites enters
the citric acid cycle and is formed, in part, by the removal of a carbon (CO₂)
from one molecule of pyruvate?
A) lactate
B) glyceraldehydes-3-phosphate
C) oxaloacetate
D) acetyl CoA
E) citrate
Answer: D
During cellular respiration, acetyl CoA accumulates in
which location?
A) cytosol
B) mitochondrial outer membrane
C) mitochondrial inner membrane
D) mitochondrial intermembrane space
E) mitochondrial matrix
Answer: E
How many carbon atoms are fed into the citric acid cycle
as a result of the oxidation of one molecule of pyruvate?
A) two
B) four
C) six
D) eight
E) ten
Answer: A
Carbon dioxide (CO₂) is released during which of the
following stages of cellular respiration?
A) glycolysis and the oxidation of pyruvate to acetyl CoA
B) oxidation of pyruvate to acetyl CoA and the citric
acid cycle
C) the citric acid cycle and oxidative phosphorylation
D) oxidative phosphorylation and fermentation
E) fermentation and glycolysis
Answer: B
A young animal has never had much energy. He is brought
to a veterinarian for help and is sent to the animal hospital for some tests.
There they discover his mitochondria can use only fatty acids and amino acids
for respiration, and his cells produce more lactate than normal. Of the
following, which is the best explanation of his condition?
A) His mitochondria lack the transport protein that moves
pyruvate across the outer mitochondrial membrane.
B) His cells cannot move NADH from glycolysis into the
mitochondria.
C) His cells contain something that inhibits oxygen use
in his mitochondria.
D) His cells lack the enzyme in glycolysis that forms
pyruvate.
E) His cells have a defective electron transport chain,
so glucose goes to lactate instead of to acetyl CoA.
Answer: A
During aerobic respiration, electrons travel downhill in
which sequence?
A) food → citric acid cycle → ATP → NAD⁺
B) food → NADH → electron transport chain → oxygen
C) glucose → pyruvate → ATP → oxygen
D) glucose → ATP → electron transport chain → NADH
E) food → glycolysis → citric acid cycle → NADH → ATP
Answer: B
