Chapter 7

Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?

Carbon dioxide

What is the correct order of electron transport compounds from best electron donor to best electron acceptor?

NADH -- Fe-S of Complex I -- Q -- Fe-S of Complex III -- Cyt c-- Cyt a of Complex IV -- O2

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH2 ... intermembrane space

Select the correct statement about cellular respiration.

Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.

is a prosthetic group present in several components of the electron transport chain.

Fe-S

Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?

Fermentation

Is CoQ used as a "fuel" during cellular respiration?

No, CoQ is a member of the electron transport chain and thus can't be metabolized as an energy molecule.

is a nonprotein organic electron carrier within the electron transport chain.

Q (ubiquinone)

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

glycolysis

Which of the following metabolic processes in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?

glycolysis

Which of the following metabolic pathways occur(s) in the cytosol of eukaryotic cells?

glycolysis and fermentation

Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?

oxidation of pyruvate to acetyl CoA and the citric acid cycle

Which of the following metabolic processes produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?

oxidative phosphorylation (chemiosmosis)

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the glucose molecule becomes

oxidized

How many NADH are produced by glycolysis?

two

The electrons stripped from glucose in cellular respiration end up in which compound?

water

In the citric acid cycle (see the figure), beginning with one molecule of isocitrate and ending with fumarate, how many ATP molecules can be made through substrate-level phosphorylation?

1

For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.

6

the complete oxidation of two molecules of glucose in cellular respiration produces about how many molecules of ATP?

60-64

Approximately how much more free energy is supplied to the electron transport chain by NADH than by FADH2?

8 kcal/mol

Which of the following statements is not true of most cellular redox reactions?

A hydrogen atom is transferred to the atom that loses an electron.

Structure A is _____.

ATP synthase

Yeast cells grown anaerobically can obtain energy by fermentation, which results in the production of

ATP, CO2, and ethanol.

Which of these enters the citric acid cycle?

Acetyl CoA

Which of the following substances is/are involved in oxidative phosphorylation?

All of the listed substances are involved in oxidative phosphorylation.

Which terms describe two atoms when they form a bond in which electrons are completely transferred from one atom to the other?

Anion and cation.

How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.)

Both electron transport and ATP synthesis would stop.

Considering the role of coenzyme Q, how do you think this product might function as a nutritional supplement to benefit the heart?

CoQ is necessary for the cellular respiration and energy production, and thus it can improve the heart work providing this organ with energy. As a result, CoQ as a nutritional supplement may contribute to more stable heartbeat.

is a multi-protein complex within the electron transport chain.

Complex III

Which stage of glucose metabolism produces the most ATP?

Electron transport and chemiosmosis

Which term describes the degree to which an element attracts electrons?

Electronegativity.

Which of the following best describes the electron transport chain of cellular respiration?

Electrons are passed from one carrier to another, releasing a little energy at each step.

Which of the following molecules donates electrons directly to the electron transport chain at the lowest energy level?

FADH2

Which of these is NOT a product of glycolysis?

FADH2

Of the following lists of electron transport compounds, which one lists them in order from the one containing electrons with the highest free energy to the one containing electrons with the lowest free energy? Note that not all electron transport compounds in the electron transport chain are listed.

FADH2 -- FMN of Complex I -- Fe-S of Complex II -- Q -- Fe-S of Complex III -- Cyt c -- Cyt a of Complex IV -- O2

NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to water in the final step of electron transport. However, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule. Which statement best explains why more ATP is made per molecule of NADH than per molecule of FADH2?

Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.

How many molecules of ATP are gained by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen?

Four

What happens at the end of the chain in the figure?

Four electrons combine with a molecule of oxygen and four protons.

Which molecule is metabolized in a cell to produce energy "currency" in the form of ATP?

Glucose

In the process of cellular respiration, what is consumed, and what is produced?

Glucose is consumed, and carbon dioxide is produced.

Of the metabolic pathways listed below, which is the most universal metabolic process associated with cellular respiration?

Glycolysis

Which step of the cellular respiration pathway can take place in the absence of oxygen?

Glycolysis

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the

H+ concentration across the membrane holding ATP synthase

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the

H+ concentration gradient across the membrane holding ATP synthase

Gaseous hydrogen burns in the presence of oxygen to form water:2H2 + O2 → 2H2 O + energyWhich molecule is oxidized and what kind of bond is formed?

Hydrogen, polar.

Where do the reactions of glycolysis occur in a eukaryotic cell?

In the cytosol

What kind of bond is formed when lithium and fluorine combine to form lithium fluoride?

Ionic. Submit

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?

It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.

In the oxidation of pyruvate to acetyl CoA, one carbon atom is released as CO2. However, the oxidation of the remaining two carbon atoms—in acetate—to CO2 requires a complex, eight-step pathway—the citric acid cycle. Consider four possible explanations for why the last two carbons in acetate are converted to CO2 in a complex cyclic pathway rather than through a simple, linear reaction. Use your knowledge of the first three stages of cellular respiration to determine which explanation is correct.

It is easier to remove electrons and produce CO2 from compounds with three or more carbon atoms than from a two-carbon compound such as acetyl CoA.

Upon completion of glycolysis, what is the fate of the majority of the potential energy contained in the original glucose molecule?

It is retained in two pyruvate molecules.

A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose?

It is stored in NADH and FADH2

Molecular oxygen (O2) has what role in aerobic cellular respiration?

It is the final electron acceptor at the end of the electron transport chain.

Which of the following describes the process of glycolysis?

It represents the first stage in the chemical oxidation of glucose by a cell.

Assuming that the x-axis tick marks will be used to identify the thyroid hormone level of each type of rat, what bars should appear on the x-axis?

Low, Normal, Elevated

In the absence of oxygen, cells need a way to regenerate which compound following glycolysis?

NAD+

When a poison such as cyanide blocks the electron transport chain, glycolysis and the citric acid cycle also eventually stop working. Which of the following is the best explanation for this?

NAD+ and FAD are not available for glycolysis and the citric acid cycle to continue.

After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of

NADH

The figure illustrates the electron transport chain. Which of the following is initially added to the chain with the highest free energy?

NADH

Which of the following statements about the electron transport chain is true?

NADH and FADH2 donate their electrons to the chain.

is the final electron acceptor of the electron transport chain.

O2 (molecular oxygen)

Which of the following statements is true of the bonds in a water molecule?

Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.

Considering this graph, under which condition is PFK more active?

PFK is more active at low ATP concentration

Based on what you know about mitochondrial electron transport and heat production, predict which rats had the highest body temperature, and which had the lowest body temperature.

Rats with elevated thyroid hormone had the highest body temperature; rats with low thyroid hormone had the lowest.

The final electron acceptor of the electron transport chain that functions in anaerobic respiration of some bacteria is

SO42−

In cellular respiration, a series of molecules forming an electron transport chain alternately accepts and then donates electrons. What is the advantage of such an electron transport chain?

The advantage of an electron transport chain is that a small amount of energy is released with the transfer of an electron between each pair of intermediates.

Identify all correct statements about the basic function of fermentation.

The basic function of fermentation is the regeneration of NAD+, which allows continued ATP production by glycolysis.

Why is the citric acid cycle called a cycle?

The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle.

How will a healthy individual's ATP production change during an eight-hour fast?

The individual's ATP production will not change significantly.

Where do the reactions of the citric acid cycle occur in eukaryotic cells?

The matrix of the mitochondrion

Which one of the following statements about the redox reactions of the electron transport chain is correct?

The redox reactions of the electron transport chain are directly coupled to the movement of protons across a membrane.

Do the results in the graph support the researchers' hypothesis?

Yes; cells that were exposed to elevated thyroid hormone levels showed increased oxygen consumption, indicating that the efficiency of the electron transport chain was reduced.

The oxygen consumed during cellular respiration is involved directly in which process or event?

accepting electrons at the end of the electron transport chain

Which of these is NOT a product of the citric acid cycle?

acetyl CoA

Which one of the following molecules is formed by the removal of a carbon (as CO2) from a molecule of pyruvate during aerobic respiration?

acetyl CoA

Which kind of metabolic poison would most directly interfere with glycolysis?

an agent that closely mimics the structure of glucose but is not metabolized

What is the primary function of beta oxidation in respiration?

breakdown of fatty acids

In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and after a few minutes radioactive oxygen atoms showed up in

carbon dioxide

Which of the following terms describes metabolic pathways that break down complex molecules to release stored energy?

catabolic pathways

Which cell type(s) had the highest rate of oxygen consumption?

cells from rats with elevated thyroid hormone

Which cell type(s) had the lowest rate of oxygen consumption?

cells from rats with low thyroid hormone

Most CO2 from catabolism is released during

citric acid cycle

Inside an active mitochondrion, most electrons follow which of the following pathways?

citric acid cycle →→ NADH →→ electron transport chain →→ oxygen

Of the following molecules in the glycolytic pathway (the process of glycolysis), the one with the most chemical energy is

fructose-1,6-bisphosphate

Under anaerobic conditions, what carbon sources can be metabolized by yeast cells to produce ATP from ADP?

glucose

Which of the following indicates a primary path by which electrons travel downhill energetically during aerobic respiration?

glucose →→ NADH →→ electron transport chain →→ oxygen

in the overall process of glycolysis and cellular respiration. ____is oxidixed and_____is reduced

glucose, oxygen

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

is a facultative anaerobe

In muscle cells, fermentation produces _____.

lactate and NAD+

A molecule becomes oxidized when it __________.

loses an electron

In cellular respiration, most ATP molecules are produced by

oxidative phosphorylation

During the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, which compound is reduced as a result of the reaction?

oxygen

The final electron acceptor of cellular respiration is

oxygen

What variable responded to thyroid hormone level (the independent variable), and what are the units for this variable?

oxygen consumption rate of liver cells, in nmol O2/min • mg cells

In mitochondria, exergonic redox reactions

provide the energy that establishes the proton gradient

What is the oxidizing agent in the following reaction?Pyruvate + NADH + H+ → Lactate + NAD+

pyruvate

In fermentation _____ is reduced and _____ is oxidized.

pyruvate ... NADH

In the citric acid cycle, ATP molecules are produced by

substrate-level phosphorylation

Which chemical process generates the ATP produced in glycolysis?

substrate-level phosphorylation

In glycolysis, ATP molecules are produced by _____.

substrate-level phosphorylation cellular respiration

Most of the NADH that delivers electrons to the electron transport chain comes from which of the following processes?

the citric acid cycle

In mitochondrial electron transport, what is the direct role of O2?

to function as the final electron acceptor in the electron transport chain

Assuming glucose is the only energy source for a cell, what fraction of the carbon dioxide produced by aerobic respiration is generated by the oxidation of pyruvate to acetyl CoA?

1/3

If 30 molecules of ATP are produced for each molecule of glucose completely oxidized to carbon dioxide and water, how many ATP molecules will be produced for each molecule of pyruvate completely oxidized to carbon dioxide and water?

14

For each glucose that enters glycolysis, _____ acetyl CoA enter the citric acid cycle.

2

In glycolysis there is a net gain of _____ ATP.

2

In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?

2 ATP

Catabolism of each molecule of glucose in glycolysis is associated with a net consumption of which of the following other molecules?

2 NAD+ and 2 ADP

Which of the following correctly lists all of the energy-containing molecules produced by the catabolism of one molecule of glucose in glycolysis?

2 NADH, 2 pyruvate, and 2 ATP

The overall efficiency of respiration (the percentage of the energy released that is saved in ATP) is approximately

34%

Assuming that the y-axis tick marks will be separated by 1.0 (0.0, 1.0, 2.0, and so on), what is the largest value that should appear on the y-axis?

9.0

In glycolysis, what starts the process of glucose oxidation?

ATP

Which statement correctly describes how this increased demand would lead to an increased rate of ATP production?

ATP levels would fall at first, decreasing the inhibition of PFK and increasing the rate of ATP production.

Brown fat cells produce a protein called thermogenin in their mitochondrial inner membrane. Thermogenin is an ion channel that facilitates diffusion of protons across the membrane. What will occur in the brown fat cells when thermogenin is present in their inner mitochondrial membranes?

ATP synthesis will decrease, and heat generation will increase.

.In glycolysis, PFK transfers a phosphate group from___to____. It is an allosteric enzyme__by high concentrations ofATP and___by high concentrations ofAMP. Thus, glycolysis is stimulated when energy charge_____

ATP, the sugar, inhibited, stimulated, falls

If a mitochondrion ran out of molecular oxygen (O2), predict which of the following situations would occur in its electron transport chain.

FMN prosthetic groups would remain reduced and NADH would have nowhere to donate electrons.

During strenuous exercise, anaerobic conditions can result if the cardiovascular system cannot supply oxygen fast enough to meet the demands of muscle cells. Assume that a muscle cell's demand for ATP under anaerobic conditions remains the same as it was under aerobic conditions. What would happen to the cell's rate of glucose utilization?

Glucose utilization would increase a lot.

Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops.

In the absence of oxygen, electron transport stops. NADH is no longer converted to NAD+, which is needed for the first three stages of cellular respiration.

How would you predict that blocking the oxidation of pyruvate would affect the levels of oxaloacetate and citrate in the citric acid cycle (see the figure)?

Oxaloacetate will accumulate, and citrate will decrease.

Which of the following is a correct description and sequence of events in cellular respiration?

Oxidation of glucose to pyruvate; oxidation of pyruvate; oxidation of acetyl-coA; oxidative phosphorylation

Most of the ATP produced in aerobic cellular respiration comes from which of the following processes?

Oxidative phosphorylation

In most cells, not all of the carbon compounds that participate in glycolysis and the citric acid cycle are converted to carbon dioxide by cellular respiration. What happens to the carbon in these compounds that does not end up as CO2?

The carbon compounds are removed from these processes to serve as building blocks for other complex molecules.

Which of the following statements about the chemiosmotic synthesis of ATP is correct?

The chemiosmotic synthesis of ATP requires that electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane.

Which process is the one in which glucose is oxidized to generate two molecules of pyruvate and in which ATP and NADH are produced?

The citric acid cycle Chemiosmosis The oxidation of pyruvate YOU WERE SURE AND CORRECT None of the listed responses is correct. Fermentation I DON'T KNOW YET none of the listed

Which of the following statements accurately describes the function of a metabolic pathway involved in cellular respiration?

The function of glycolysis is to begin catabolism by breaking glucose into two molecules of pyruvate, with a net yield of two ATP.

Which statement about the citric acid cycle is correct?

The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle.

Which of the following describes the result of transferring an electron from a less electronegative atom to a more electronegative atom?

The more electronegative atom is reduced, and energy is released.

If muscle cells in the human body consume O2 faster than it can be supplied, which of the following is likely to result?

The muscle cells will have trouble making enough ATP to meet demands and the cells will not be able to carry out oxidative phosphorylation. The muscle cells will have trouble making enough ATP to meet demands. I AM UNSURE All of the listed events will occur. The cells will consume glucose at an increased rate. The cells will not be able to carry out oxidative phosphorylation. I DON'T KNOW YET all of the listed

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

The pHpH of the matrix increases.

True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.

True

True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.

True

In the citric acid cycle, for each pyruvate that enters the cycle, one ATP, three NADH, and one FADH2 are produced. For each glucose molecule that enters glycolysis, how many ATP, NADH, and FADH2 are produced in the citric acid cycle?

Two ATP, six NADH, two FADH2

The electron transport chain involved in cellular respiration is located in/on the

inner membrane of the mitochondrion

The proximate (immediate) source of energy for oxidative phosphorylation is

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient

Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?

mitochondrial intermembrane space

donates electrons to the electron transport chain.

nadh

Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?

pyruvate, ATP, and NADH

What is the source of the energy used to generate the proton gradient across the inner mitochondrial membrane?

redox reactions in the electron transport chain

Which chemical process generates the ATP produced in the citric acid cycle?

substrate level phosphorylation

In glycolysis, ATP molecules are produced by

substrate-level phosphorylation

What variable did the researchers intentionally vary in the experiment, and what are the units for this variable?

thyroid hormone level of the rats chosen for the experiment, in relative units

Which of the following is the most important result of the process of cellular respiration in biological systems?

transforming the energy in glucose and related molecules in a chemical form that cells can use for work