Cellular Respiration and Energy Production, Exams of Biology

Download Cellular Respiration and Energy Production and more Exams Biology in PDF only on Docsity!

Life 120 Chapter 7 Questions

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 - correct 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. - correct 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. - correct 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. -

correct 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. - correct 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. - correct 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. - correct 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. - correct 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 - correct 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+. - correct 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 - correct

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. - correct 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. - correct

answer D

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 - correct 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 - correct answer C

In prokaryotes, the respiratory electron transport chain is located A) in the mitochondrial inner membrane. B) in the mitochondrial outer membrane. C) in the plasma membrane. D) in the cytoplasm.

E) in the bacterial outer membrane. - correct answer C

Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur? A) in photosynthetic cells in the light, while photosynthesis occurs concurrently B) in nonphotosynthesizing cells only C) in cells that are storing glucose only D) in all cells all the time

E) in photosynthesizing cells in the light and in other tissues in the dark - correct answer D

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 - correct answer B

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% - correct 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. - correct 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 - correct 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. - correct 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 pyruvate, and 2 ATP.

E) 6 CO2, 2 pyruvate, and 30 ATP. - correct 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. - correct 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. -

correct 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 - correct 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. - correct 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) 2 B) 4 C) 6 D) 8

E) 10 - correct 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 - correct answer B

A young dog has never had much energy. He is brought to a veterinarian for help and she decides to conduct several diagnostic tests. She discovers that the dog's 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 the dog's 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. - correct answer A

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/

B) 1/

C) 1/

D) 2/

E) all of it - correct 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 - correct 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. - correct 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 + ℗i

E) FADH2 - correct 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 - correct 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 - correct 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-) - correct answer C

In chemiosmosis, what is the most direct source of energy that is used to convert ADP + ℗i to ATP? A) energy released as electrons flow through the electron transport system B) energy released from substrate-level phosphorylation C) energy released from dehydration synthesis reactions D) energy released from movement of protons through ATP synthase, down their electrochemical gradient

E) No external source of energy is required because the reaction is exergonic. - correct 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 - correct 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. - correct answer D

When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is A) the formation of ATP. B) the reduction of NAD+. C) the restoration of the Na+/K+ balance across the membrane. D) the creation of a proton-motive force.

E) the lowering of pH in the mitochondrial matrix. - correct 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 - correct answer D

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) - correct 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-

E) 60-64 - correct 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. - correct answer B

If a cell is able to synthesize 30 ATP molecules for each molecule of glucose completely oxidized to carbon dioxide and water, approximately 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) 26 - correct answer D

What is proton-motive force? A) the force required to remove an electron from hydrogen B) the force provided by a transmembrane hydrogen ion 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+ - correct 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. - correct 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. - correct 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. - correct answer C

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. - correct answer D

In vertebrate animals, brown fat tissue's color is due to abundant blood vessels and capillaries. White fat tissue, on the other hand, is specialized for fat storage and contains relatively few blood vessels or capillaries. Brown fat cells have a specialized protein that dissipates the proton-motive force across the mitochondrial membranes. Which of the following might be the function of the brown fat tissue? A) to increase the rate of oxidative phosphorylation from its few mitochondria B) to allow the animals to regulate their metabolic rate when it is especially hot C) to increase the production of ATP D) to allow other membranes of the cell to perform mitochondrial functions

E) to regulate temperature by converting most of the energy from NADH oxidation to heat - correct

answer E

What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions? A) glucose B) ethanol C) pyruvate D) lactic acid

E) either ethanol or lactic acid - correct answer A

Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy? A) glucose B) proteins C) fatty acids D) glucose, proteins, and fatty acids E) Such yeast cells will not be capable of catabolizing any food molecules, and will therefore die. -

correct answer A

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 - correct 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) - correct answer A

Which of the following occur(s) 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 - correct 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 - correct 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 - correct 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. - correct answer A

In alcohol fermentation, NAD+ is regenerated from NADH by A) reduction of acetaldehyde to ethanol (ethyl alcohol). B) oxidation of pyruvate to acetyl CoA.

C) reduction of pyruvate to form lactate.

D) oxidation of ethanol to acetyl CoA. E) reduction of ethanol to pyruvate. - correct answer A

One function of both alcohol fermentation and lactic acid fermentation is to A) reduce NAD+ to NADH. B) reduce FAD+ to FADH2. C) oxidize NADH to NAD+.

D) reduce FADH2 to FAD+. E) do none of the above. - correct answer C

An organism is discovered that thrives both in the presence and absence of oxygen in the air. Curiously, the consumption of sugar increases as oxygen is removed from the organism's environment, even though the organism does not gain much weight. This organism A) must use a molecule other than oxygen to accept electrons from the electron transport chain. B) is a normal eukaryotic organism. C) is photosynthetic.

D) is an anaerobic organism. E) is a facultative anaerobe. - correct answer E

Which statement best supports the hypothesis that glycolysis is an ancient metabolic pathway that originated before the last universal common ancestor of life on Earth? A) Glycolysis is widespread and is found in the domains Bacteria, Archaea, and Eukarya. B) Glycolysis neither uses nor needs O2. C) Glycolysis is found in all eukaryotic cells. D) The enzymes of glycolysis are found in the cytosol rather than in a membrane-enclosed organelle. E) Ancient prokaryotic cells, the most primitive of cells, made extensive use of glycolysis long before

oxygen was present in Earth's atmosphere. - correct answer A

65. Why is glycolysis considered to be one of the first metabolic pathways to have evolved? A) It produces much less ATP than does oxidative phosphorylation. B) It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms. C) It is found in prokaryotic cells but not in eukaryotic cells. D) It relies on chemiosmosis, which is a metabolic mechanism present only in the first cells' prokaryotic cells.

E) It requires the presence of membrane-enclosed cell organelles found only in eukaryotic cells. -

correct answer B

When an individual is exercising heavily and when the muscle becomes oxygen-deprived, muscle cells convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells? A) It is converted to NAD+. B) It produces CO2 and water. C) It is taken to the liver and converted back to pyruvate. D) It reduces FADH2 to FAD+.

E) It is converted to alcohol. - correct answer C

A mutation in yeast makes it unable to convert pyruvate to ethanol. How will this mutation affect these yeast cells? A) The mutant yeast will be unable to grow anaerobically. B) The mutant yeast will grow anaerobically only when given glucose. C) The mutant yeast will be unable to metabolize glucose. D) The mutant yeast will die because they cannot regenerate NAD+ from NAD. E) The mutant yeast

will metabolize only fatty acids. - correct answer A

You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave her body? A) It was released as CO2 and H2O. B) It was converted to heat and then released. C) It was converted to ATP, which weighs much less than fat. D) It was broken down to amino acids and eliminated from the body. E) It was converted to urine

and eliminated from the body. - correct answer A

What is the purpose of beta oxidation in respiration? A) oxidation of glucose B) oxidation of pyruvate C) feedback regulation

D) control of ATP accumulation E) breakdown of fatty acids - correct answer E

Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle? A) pyruvate B) malate or fumarate

C) acetyl CoA D) α-ketoglutarate

E) succinyl CoA - correct answer C

During intense exercise, as skeletal muscle cells switch to fermentation, the human body will increase its catabolism of A) fats only. B) carbohydrates only. C) proteins only.

D) fats, carbohydrates, and proteins. E) fats and proteins only. - correct answer B

For each mole of glucose (C6H12O6) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle (see Figure 7.1)? A) 2 B) 4 C) 6 D) 12

E) 3 - correct answer B

If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citric acid in the citric acid cycle shown? A) There will be no change in the levels of oxaloacetate and citric acid. B) Oxaloacetate will decrease and citric acid will accumulate. C) Oxaloacetate will accumulate and citric acid will decrease. D) Both oxaloacetate and citric acid will decrease.

E) Both oxaloacetate and citric acid will accumulate. - correct answer C

Starting with citrate, which of the following combinations of products would result from three acetyl CoA molecules entering the citric acid cycle A) 1 ATP, 2 CO2, 3 NADH, and 1 FADH B) 2 ATP, 2 CO2, 3 NADH, and 3 FADH C) 3 ATP, 3 CO2, 3 NADH, and 3 FADH2 D) 3 ATP, 6 CO2, 9 NADH, and 3 FADH2 E) 38 ATP, 6 CO2, 3

NADH, and 12 FADH2 - correct answer D

or each molecule of glucose that is metabolized by glycolysis and the citric acid cycle, what is the total number of NADH + FADH2 molecules produced? A) 4 B) 5 C) 6 D) 10

E) 12 - correct answer E

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A.

1. These three steps result in the formation of A) acetyl CoA, O2, and ATP. B) acetyl CoA, FADH2, and CO2. C) acetyl CoA, FAD, H2, and CO2. D) acetyl CoA, NADH, H+, and CO2.

E) acetyl CoA, NAD+, ATP, and CO2. - correct answer D

How does the addition of coenzyme A, a sulfur-containing molecule derived from a B vitamin, function in the subsequent reaction? A) It provides the sulfur needed for the molecule to enter the mitochondrion. B) It utilizes this portion of a B vitamin, which would otherwise be a waste product from another pathway. C) It provides a relatively unstable molecule whose acetyl portion can be readily transferred to a compound in the citric acid cycle.

D) It drives the reaction that regenerates NAD+. E) It removes one molecule of CO2. - correct

answer C

Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate? A) lactate B) glyceraldehyde-3-phosphate C) oxaloacetate D) acetyl CoA

E) citrate - correct answer D

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the A) oxidation of glucose and other organic compounds. B) flow of electrons down the electron transport chain. C) affinity of oxygen for electrons.

D) H+ movement down its concentration gradient. E) transfer of phosphate to ADP. - correct

answer D

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule? A) the citric acid cycle B) the electron transport chain C) glycolysis

D) synthesis of acetyl CoA from pyruvate E) reduction of pyruvate to lactate - correct answer C

In mitochondria, exergonic redox reactions A) are the source of energy driving prokaryotic ATP synthesis. B) are directly coupled to substrate- level phosphorylation. C) provide the energy that establishes the proton gradient. D) reduce carbon atoms to carbon dioxide.

E) use ATP to pump H+ out of the mitochondrion. - correct answer C

The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is A) oxygen. B) water. C) NAD+. D) pyruvate.

E) ADP. - correct answer A

What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ → Lactate + NAD+ A) oxygen B) NADH C) NAD+ D) lactate

E) pyruvate - correct answer E

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs? A) The pH of the matrix increases. B) ATP synthase pumps protons by active transport. C) The electrons gain free energy. D) The cytochromes phosphorylate ADP to form ATP.

E) NAD+ is oxidized. - correct answer A

Most CO2 from catabolism is released during A) glycolysis. B) the citric acid cycle. C) lactate fermentation. D) electron transport.

E) oxidative phosphorylation - correct answer B