Chapter 7: LearningCurve

Imagine that a eukaryotic cell carries a mutation impairing its ability to phosphorylate glucose during glycolysis. What is a likely result of this mutation? Glucose could move out of the cell, slowing cellular respiration. Because phosphorylation stabilizes glucose, glucose would spontaneously form pyruvate. High (possibly toxic) levels of glucose would accumulate in the cell. Without the phosphorylation of glucose, glycolysis would consist entirely of exergonic reactions. More pyruvate would be formed at the end of glycolysis.

Glucose could move out of the cell, slowing cellular respiration.

Which of the following does not occur during the third phase of glycolysis? pyruvate production ATP synthesis None of the other answer options is correct. oxygen consumption the transfer of high-energy electrons to NAD+

oxygen consumption

Another name for acetyl-CoA synthesis, is: pyruvate oxidation. glycolysis. substrate-level phosphorylation. oxidative phosphorylation. pyruvate reduction.

pyruvate oxidation.

In the absence of oxygen, fermentation: regenerates NAD+ from the reduction of pyruvate. regenerates NAD+ from the oxidation of pyruvate. generates ATP from the oxidation of pyruvate. generates ATP from the reduction of pyruvate. None of the other answer options is correct.

regenerates NAD+ from the reduction of pyruvate.

Beta-oxidation of fatty acids does not directly produce: acetyl-CoA. electrons transferred to NAD+. ATP. electrons transferred to FADH.

ATP

Lactic acid fermentation occurs in: Select all that apply. fungi and bacteria. plants and bacteria. animals and plants. bacteria and animals. animals and fungi.

bacteria and animals.

ow did the earliest organisms on Earth most likely produce ATP? by pyruvate oxidation by oxidative phosphorylation by glycolysis by the citric acid cycle

by glycolysis

Cellular respiration is a series of _____ reactions. carboxylation glycolytic anabolic phosphorylation catabolic

catabolic

Malate is both the starting and ending product of the citric acid cycle. true false

false ( starting molecule, oxaloacetate, is regenerated at the end)

Pyruvate oxidation produces a large amount of ATP. true false

false (Pyruvate is oxidized in the mitochondrial matrix, forming acetyl-CoA, the first substrate in the citric acid cycle.)

In what organelle is pyruvate oxidation carried out in a cell? mitochondrion chloroplast nucleus Golgi apparatus endoplasmic reticulum

mitochondrion

Which is the only reaction in the citric acid cycle that produces ATP by substrate-level phosphorylation? the formation of malate the formation of fumarate the formation of citrate the formation of succinate the formation of oxaloacetate

the formation of succinate

The electron transport chain is part of: fermentation. the citric acid cycle. glycolysis. oxidative phosphorylation. pyruvate oxidation.

oxidative phosphorylation.

In cellular respiration, glucose is _____ to CO2 and oxygen is _____ to water. reduced; oxidized oxidized; reduced deoxygenated; phosphorylated phosphorylated; deoxygenated oxidized; oxidized

oxidized; reduced

When an electron is transferred from NADH to CoQ, NADH is _____ and CoQ is _____. oxidized; reduced reduced; oxidized oxidized; oxidized reduced; reduced

oxidized; reduced

The final electron acceptor of the electron transport chain is: NAD+. oxygen. coenzyme Q. ATP synthase. cytochrome C.

oxygen

In the second phase of glycolysis: phosphorylated sugar molecule is cleaved and the products rearranged. phosphate groups are added to glucose. ATP is generated by oxidative phosphorylation. ATP is generated by substrate-level phosphorylation. NAD+ is reduced to NADH.

phosphorylated sugar molecule is cleaved and the products rearranged

The citric acid cycle is a cycle because the starting molecule, _____, is regenerated at the end. fructose 6-diphosphate pyruvate acetyl-CoA oxaloacetate citrate

oxaloacetate

A single molecule of glucose requires _____ "turn(s)" through the citric acid cycle for its chemical energy to be completely harvested. 1 2 4 3 5

2

After pyruvate oxidation, the chemical energy of how many carbons of the original glucose molecule is converted to chemical energy in the form of ATP in the remaining steps of cellular respiration? 4 1 2 5 3

4

The enzyme phosphofructokinase-1 (PFK-1) is thought of as a metabolic "valve" that regulates the rate of glycolysis. Which of the following correctly identifies its allosteric activators and inhibitors and their actions? ADP—activator; ATP—activator AMP—activator; CoQ—inhibitor CoQ—activator; citrate—inhibitor ATP—activator; AMP—inhibitor ADP—activator; citrate—inhibitor

ADP—activator; citrate—inhibitor

During the citric acid cycle: ATP is synthesized by substrate-level phosphorylation. fuel molecules are completely reduced. high-energy electrons are removed from NAD+ and FADH. ATP is synthesized by oxidative phosphorylation.

ATP is synthesized by substrate-level phosphorylation.

During a long bout of sustained exercise, in which order will your body's energy stores/sources be used? fatty acids, glycogen stored in the liver, glycogen stored in the muscle, ATP stored in the muscle ATP stored in muscle, glycogen stored in the liver, glycogen stored in the muscle, fatty acids ATP stored in muscle, glycogen stored in muscle, glycogen stored in the liver, fatty acids ATP stored in muscle, fatty acids, glycogen stored in the muscle, glycogen stored in the liver glycogen stored in muscle, ATP stored in the muscle, glycogen stored in the liver, fatty acids

ATP stored in muscle, glycogen stored in muscle, glycogen stored in the liver, fatty acids

For the potential energy of a proton gradient to be converted to the chemical energy of ATP, the movement of protons down their electrochemical gradient must be coupled with ATP synthesis. This coupling is made possible by: coenzyme Q. ATP synthase. cytochrome c. protein complex IV. oxygen.

ATP synthase.

Which of the following statements are true regarding pyruvate oxidation? This process occurs within the matrix of mitochondria. This process constitutes the second stage of cellular respiration. The process produces both CO2 and acetyl-CoA. The process yields no ATP via substrate-level phosphorylation. All of these choices are correct.

All of these choices are correct.

A researcher is studying a population of eukaryotic cells. He notices that—regardless of the presence of ATP or ADP—the PFK-1 enzyme fails to function properly. Why? These cells may carry a mutation that alters the active site of the PFK-1 enzyme. These cells may carry a mutation that affects binding sites of the PFK-1 enzyme. These cells may carry a mutation that causes an over-production of citrate. Any of these choices may be correct.

Any of these choices may be correct.

Lactic acid and ethanol fermentation differ in that: FADH2 is oxidized to FADH in lactic acid fermentation, but NADH is oxidized to NAD+ in ethanol fermentation. NADH is oxidized to NAD+ in lactic acid fermentation, but FADH2 is oxidized to FADH in ethanol fermentation. ethanol fermentation produces ATP by substrate level phosphorylation, but lactic acid fermentation does not. lactic acid fermentation produces ATP by substrate level phosphorylation, but ethanol fermentation does not. Ethanol fermentation produces CO2, but lactic acid fermentation does not.

Ethanol fermentation produces CO2, but lactic acid fermentation does not.

ATP is not generated directly in the citric acid cycle; instead, an intermediate is first generated by substrate-level phosphorylation. The intermediate is: GDP. GTP. acetyl-CoA. oxaloacetate. cAMP.

GTP

Some present-day bacteria use a system of anaerobic respiration characterized by an electron transport chain analogous to that found in aerobic organisms. Which of the following correctly characterizes the anaerobic electron transport chain? It uses oxygen as a final electron acceptor. It is embedded in the outer mitochondrial membrane rather than the inner mitochondrial membrane. It establishes a proton gradient between the cytoplasm and the extracellular fluid. It establishes a proton gradient between the intermembrane space and the cytoplasm. None of these answer options accurately characterizes the anaerobic electron transport chain.

It establishes a proton gradient between the cytoplasm and the extracellular fluid.

The inputs to glycolysis do not include: NADH. glucose. NAD+. ADP. Pi.

NADH

he inputs to glycolysis do not include: NADH. glucose. NAD+. ADP. Pi.

NADH

When a single pyruvate is converted to acetyl-CoA, the other products of the reaction are: NADH and CO2. CO2 and ATP. ATP and NADH. Pi and FADH2. FADH2 and ATP.

NADH and CO2.

Which of the following statements is true regarding pyruvate and glucose? Glucose easily passes in and out of mitochondria, and can often be found in the mitochondrial matrix. Pyruvate is typically "trapped" in the intermembrane space of mitochondria, where it is oxidized to form acetyl-CoA. Glucose and pyruvate are remarkably similar in structure, with both molecules possessing a ring shape. Both glucose and pyruvate can feed directly into the citric acid cycle, although acetyl-CoA is the preferred reactant for this process. None of the other answer options is correct.

None of the other answer options is correct. ( a single molecule of glucose forms two molecules of pyruvate during glycolysis)

Which of the following statements is true regarding pyruvate oxidation? Pyruvate oxidation directly follows the citric acid cycle during cellular respiration. Pyruvate oxidation forms the same number of NADH (per glucose molecule) as glycolysis. Pyruvate oxidation ends with the oxidation of an acetyl group, which forms CO2. Like glycolysis, pyruvate oxidation is carried out in the mitochondria.

Pyruvate oxidation forms the same number of NADH (per glucose molecule) as glycolysis.

We consume a variety of carbohydrates that are digested into a variety of different sugars. How do these different sugars enter glycolysis? All sugars are converted to fructose 6-phosphate and enter glycolysis at phase 1, step 3. All sugars are converted to glyceraldehyde 3-phosphate and enter glycolysis at phase 3, step 6. All sugars are converted to glucose 6-phosphate and enter glycolysis at phase 1, step 2. Sugars are converted to various forms and enter glycolysis at various stages. None of the other answer options is correct.

Sugars are converted to various forms and enter glycolysis at various stages.

A researcher is comparing the amount of proteins contained in inner and outer mitochondrial membranes. What do you expect she will find? The amount of proteins is greater in the outer membrane. The amount of proteins is equivalent in the outer and inner membranes. The amount of proteins is greater in the inner membrane.

The amount of proteins is greater in the inner membrane.

Which of the following statements is true regarding the equation C6H12O6 + 6O2 →6CO2+ 6H2O + energy? The oxygen atoms in both CO2 and H2O are electronegative. Glucose could be considered a reducing agent. The oxygen atoms in both CO2 and H2O are electronegative, and glucose is considered a reducing agent. The movement of hydrogen atoms in reactions involving C6H12O6 and H2O yields no information regarding the movement of electrons. In the production of CO2 from glucose, the oxygen atoms lose electrons and the carbon atom is oxidized.

The oxygen atoms in both CO2 and H2O are electronegative, and glucose is considered a reducing agent.

Energy released by transferring electrons along the electron transport chain is stored as potential energy in the form of: coenzyme Q. redox couples. a proton gradient. ATP. ATP synthase.

a proton gradient.

Glycolysis is: aerobic. anaerobic. aerobic in some organisms but anaerobic in others. aerobic in some tissues but anaerobic in others. None of the other answer options is correct.

anaerobic (requires absence of free oxygen)

The breakdown of fatty acids takes place by a process called: beta-oxidation. pyruvate oxidation. electron transport. glycolysis. oxidative phosphorylation.

beta-oxidation.

Phosphorylating glucose during phase 1 of glycolysis: releases phosphorylated glucose from cells. destabilizes the glucose molecule so that it can be broken down in phase 2. provides electrons to reduce NAD+ in phase 3. provides electrons to reduce FADH in phase 3. None of the other answer options is correct.

destabilizes the glucose molecule so that it can be broken down in phase 2.

In the first three stages of cellular respiration, the chemical energy in glucose is transferred to: electron carriers and ATP. ATP and cytochrome b. cytochrome b and coenzyme Q. proton pumps and ATP. only coenzyme Q.

electron carriers and ATP.

The majority of the energy generated in the citric acid cycle is in the form of: GTP produced by substrate-level phosphorylation. electrons donated to NAD+ and FAD+. ATP produced by oxidative phosphorylation. GTP produced by oxidative phosphorylation. ATP produced by substrate-level phosphorylation.

electrons donated to NAD+ and FAD+.

The proteins of the electron transport chain are: embedded in both mitochondrial membranes. located in the mitochondrial matrix. embedded in the outer mitochondrial membrane. embedded in the inner mitochondrial membrane. located in the intermembrane space of mitochondria.

embedded in the inner mitochondrial membrane.

When glucose is broken down in a cell, all of the energy it stores is released simultaneously, not in a stepwise process. true false

false (In stage 1, glucose is partially broken down to make pyruvate and energy is transferred to ATP and reduced electron carriers, a process known as glycolysis. In stage 2, pyruvate is oxidized to another molecule called acetyl-coenzyme A (acetyl-CoA), producing reduced electron carriers and releasing carbon dioxide. Acetyl-CoA enters stage 3, the citric acid cycle, also called the tricarboxylic (TCA) cycle or the Krebs cycle. In this series of chemical reactions, the acetyl group is completely oxidized to carbon dioxide and energy is transferred to ATP and reduced electron carriers. The amount of energy transferred to ATP and reduced electron carriers in this stage is nearly twice that of stages 1 and 2 combined. Stage 4 is oxidative phosphorylation. In this series of reactions, reduced electron carriers generated in stages 1-3 donate electrons to the electron transport chain and a large amount of ATP is produced. In eukaryotes, glycolysis takes place in the cytoplasm, and pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation all take place in mitochondria. The electron transport chain is made up of proteins and small molecules associated with the inner mitochondrial membrane (Chapter 5). In some bacteria, these reactions take place in the cytoplasm, and the electron transport chain is located in the plasma membrane.)

Pyruvate oxidation is remarkably similar to glycolysis in that when one molecule of pyruvate enters into a mitochondrion, two molecules of acetyl-CoA are formed. true false

false (Pyruvate is transported into the mitochondrial matrix, where it is converted into acetyl-CoA )

During the action of ATP synthase, the kinetic energy of the proton gradient is transformed into potential energy. true false

false (The proton gradient is a source of potential energy and STORES potential energy)

In cellular respiration, oxygen: gains electrons and is an oxidizing agent. loses electrons and is a reducing agent. gains electrons and is a reducing agent. loses electrons and is an oxidizing agent. None of the other answer options is correct.

gains electrons and is an oxidizing agent.

Excess glucose is stored in large branched molecules of: starch in bacteria. glycogen in plants. glycogen and starch in both animals and plants. glycogen in animals. starch in animals.

glycogen in animals.

Starting with glycolysis, lactic acid and ethanol fermentation generate only two ATP molecules per glucose molecule. The remaining chemical energy from the glucose is found primarily in: GTP. NADH. FADH2. lactic acid and ethanol. CO2.

lactic acid and ethanol.

During pyruvate oxidation, pyruvate is broken down into CO2 and an acetyl group. The CO2 is: less oxidized than the acetyl group. more reduced than the acetyl group. more energetic than the acetyl group. less energetic than the acetyl group. None of the other answer options is correct.

less energetic than the acetyl group.

he chemical bonds of carbohydrates and lipids have high potential energy because: they are strong oxidizing agents. they are strong reducing agents. many of these bonds are C—C and C—H bonds. they are easy to phosphorylate. they are easy to hydrolyze.

many of these bonds are C—C and C—H bonds.

In eukaryotes, pyruvate oxidation takes place in the: outer mitochondrial membrane. cytoplasm. inner mitochondrial membrane. intermembrane space of mitochondria. mitochondrial matrix.

mitochondrial matrix.

The citric acid cycle takes place in the: cytoplasm. intermembrane space of mitochondria. outer mitochondrial membrane. inner mitochondrial membrane. mitochondrial matrix.

mitochondrial matrix.

Fermentation occurs in: only in bacteria and plants. some aerobic organisms, such as yeast, even in the presence of oxygen. anaerobic organisms only.

some aerobic organisms, such as yeast, even in the presence of oxygen.

In glycolysis, ATP is synthesized by: substrate-level phosphorylation. both substrate level and oxidative phosphorylation. oxidative phosphorylation. electron carriers. redox reactions.

substrate-level phosphorylation.

Although glycolysis produces four molecules of ATP by substrate-level phosphorylation, the net gain of ATP for the cell is two molecules. This is due to the fact that glycolysis is—at first—endergonic. true false

true

The ATP produced during glycolysis is the result of substrate-level phosphorylation. true false

true

Which of the following is not one of the net final products of glycolysis? two molecules of ATP two molecules of acetyl-CoA two molecules of NADH two molecules of pyruvate

two molecules of acetyl-CoA

At the end of glycolysis, the carbon molecules originally found in the starting glucose molecule are in the form of: two ATP molecules. one pyruvate molecule. two pyruvate molecules. four ATP molecules. two NADH molecules.

two pyruvate molecules.