Chapter 9 Cellular Respiration

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The reaction A --> B + C + heat is released in a(n) _____ reaction.

anabolic
exergonic
exchange
endergonic
dehydration synthesis

exergonic

A(n) _____ reaction occurs spontaneously.

exergonic
anabolic
kinetic
chemical
endergonic

exergonic

Which of these reactions requires a net input of energy from its surroundings?

endergonic
exergonic
hydrolysis
catabolic
ATP --> ADP + P

endergonic

The products of endergonic reactions have more potential energy than the reactants

In cells, what is usually the immediate source of energy for an endergonic reaction?

glucose
ADP
sugar
ATP
as spontaneous reactions, endergonic reactions do not need an addition of energy

ATP

The hydrolysis of ATP provides the energy needed for an endergonic reaction.

The reaction ADP + P --> ATP is a(n) _____ reaction.

exergonic
endergonic
chemical
hydrolysis
spontaneous

endergonic

Energy has been acquired from the surroundings.

The energy for an endergonic reaction comes from a(n) _____ reaction.

glucose + glucose --> maltose
ADP + P --> ATP
anabolic
synthesis
exergonic

exergonic

The energy released by an exergonic reaction can be used to drive an endergonic reaction.

What is the fate of the phosphate group that is removed when ATP is converted to ADP?

It is acquired by a reactant in a spontaneous reaction.
It is acquired by a reactant in an endergonic reaction.
It is acquired by a reactant in an exergonic reaction.
It is broken down into one phosphorus and four oxygen atoms.
It is used to convert an ATP into an AQP.

It is acquired by a reactant in an endergonic reaction

Select the INCORRECT association.

exergonic ... spontaneous
potential energy ... positional energy
enzyme ... protein
exergonic ... uphill
kinetic energy ... motion

exergonic...uphill

exergonic reactions release energy

What is energy coupling?

a description of the energetic relationship between the reactants and products in an exergonic reaction
the hydrolysis of ATP to ADP + P
the use of energy released from an exergonic reaction to drive an endergonic reaction
the use of an enzyme to reduce EA
a barrier to the initiation of a reaction

the use of energy released from an exergonic reaction to drive an endergonic reaction

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

Electronegativity.
Reduction.
Oxidation.
Polarity.

Electronegativity.

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

Polar and nonpolar.
Anion and cation.
Ionic and covalent.
Proton and electron.

anion and cation

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

The electron in each hydrogen atom is completely transferred to the oxygen atom, and each hydrogen atom has a net charge of +1.
Oxygen acts as the electron acceptor and is oxidized.
There is equal sharing of the electrons between the oxygen atom and the two hydrogen atoms, and the net charge is zero.
Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.

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

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

The electron acceptor is reduced.
The reactant that is oxidized loses electrons.
A hydrogen atom is transferred to the atom that loses an electron.
Changes in potential energy can be released as heat.

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

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

Nonpolar covalent.
Ionic.
Redox.
Polar covalent.

Ionic

Gaseous hydrogen burns in the presence of oxygen to form water:

2H2 + O2 → 2H2 O + energy

Which molecule is oxidized and what kind of bond is formed?

Hydrogen, polar.
Oxygen, polar.
Oxygen, nonpolar.
Hydrogen, nonpolar

Hydrogen, polar.

A cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen when an athlete exhausts his or her ATP supply?

ATP is transported into the cell from the circulatory system.
He or she has to sit down and rest.
Catabolic processes are activated that generate more ATP.
Other cells take over, and the muscle cells that have used up their ATP cease to function.

Catabolic processes are activated that generate more ATP.

Refer to the figure in the text. What characteristic of this molecule (ATP) is responsible for its high energy level?

the CH bonds of the ribose sugar
the closely spaced negative charges associated with the phosphate groups
the phosphorus atoms in the phosphate groups
the three phosphate groups

the closely spaced negative charges associated with the phosphate groups

How many NADH are produced by glycolysis?

4
2
1
5
3

Two NADH molecules are produced by glycolysis.

In glycolysis, ATP molecules are produced by _____.

photophosphorylation
substrate-level phosphorylation
photosynthesis
cellular respiration
oxidative phosphorylation

substrate-level phosphorylation

A phosphate group is transferred from glyceraldehyde phosphate to ADP.

Which of these is NOT a product of glycolysis?

pyruvate
NADH
FADH2
ATP

FADH2 is a product of the citric acid cycle.

In glycolysis, what starts the process of glucose oxidation?

NADPH
hexokinase
ADP
ATP
FADH2

ATP

In glycolysis there is a net gain of _____ ATP.

3
4
1
5
2

2

It takes 2 ATP to produce 4 ATP.

Which of these is an example of negative feedback?

As a blood clot begins to form, the process of its formation gets faster and faster.
After you eat, glucagon stimulates an increase in blood sugar levels.
After you eat, insulin stimulates the lowering of blood sugar levels.
The digestive enzyme pepsinogen is converted to pepsin by the action of hydrochloric acid; pepsin itself can then convert pepsinogen into pepsin.
Once labor begins, contractions increase in frequency and intensity.

After you eat, insulin stimulates the lowering of blood sugar levels.

In the phosphofructokinase molecule shown in the figure below, the active site has a much higher affinity for ATP than the regulatory site does. Which answer best summarizes what the consequences would be if the regulatory site had a much higher affinity for ATP than the active site did?

Glucose oxidation would occur faster at low ATP concentrations.
Glucose oxidation would be inhibited even if ATP were scarce in the cell.
Glucose oxidation would occur via a completely different metabolic pathway.
Glucose oxidation would be inhibited only at high ATP concentrations.

Glucose oxidation would be inhibited even if ATP were scarce in the cell.

Two ATP molecules are expended in the energy investment phase of glycolysis. Why is this energy needed to begin the process of glucose catabolism?

Some energy must be invested to make the glucose molecule unstable and begin the process of catabolism.
It is needed because glycolysis is considered an exergonic process which always requires input of energy from ATP.
It is needed to generate the electron carrier NAD+.
It is needed to induce the enzymes of glycolysis.

Some energy must be invested to make the glucose molecule unstable and begin the process of catabolism.

Canine phosphofructokinase (PFK) deficiency afflicts springer spaniels, affecting an estimated 10% of the breed. PFK is the glycolytic enzyme that phosphorylates fructose-1-phosphate and catalyzes the committed step in glycolysis. Given its critical role in glycolysis, one implication of the genetic defect resulting in PFK deficiency in dogs is _____.

early embryonic mortality
an intolerance for exercise
a reduced life span
elevated blood-glucose levels in the dog's blood

an intolerance for exercise

Substrate-level phosphorylation occurs within a metabolic pathway where sufficient energy is released by a given chemical reaction to drive the synthesis of ATP from ADP and phosphate. In which of the following metabolic pathways is substrate-level phosphorylation exhibited?

in both glycolysis and the Krebs cycle
in glycolysis
in the Krebs cycle
during oxidative phosphorylation

in both glycolysis and the Krebs cycle

The reactions of pyruvate processing, the citric acid cycle, and the electron transport chain occur within the _____ in the cell.

nucleus
cytoplasm
mitochondria
chloroplast

mitochondria

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.

More ATP is produced per CO2 released in cyclic processes than in linear processes.
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.
Redox reactions that simultaneously produce CO2 and NADH occur only in cyclic processes.
Cyclic processes, such as the citric acid cycle, require a different mechanism of ATP synthesis than linear processes, such as glycolysis.

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.

Which of these enters the citric acid cycle?

NADH + H+
glucose
acetyl CoA
G3P
pyruvate

acetyl CoA

In the citric acid cycle, ATP molecules are produced by _____.

photosynthesis
oxidative phosphorylation
cellular respiration
substrate-level phosphorylation
photophosphorylation

substrate-level phosphorylation

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

NADH + H+
ATP
CO2
acetyl CoA
FADH2

acetyl CoA

Following glycolysis and the Krebs cycle, but before the electron transport chain and oxidative phosphorylation, the carbon skeleton of glucose has been broken down to CO2 with some net gain of ATP. Most of the energy from the original glucose molecule at that point in the process, however, is in the form of _____.

pyruvate
glucose
acetyl-CoA
NADH

NADH

If you were to add one of the eight Krebs cycle intermediates to the culture medium of yeast growing in the laboratory, what do you think would happen to their rates of ATP and carbon dioxide production?

Rates of ATP and carbon dioxide production would probably both decrease.
The rates of ATP production and carbon dioxide production would both increase.
The rate of ATP production would decrease, but the rate of carbon dioxide production would increase.
There would be no change in ATP production, but we would observe an increased rate of carbon dioxide production.

The rates of ATP production and carbon dioxide production would both increase.

What is the function of coenzyme A in the Krebs cycle?

It is the coenzyme of acetylation reactions.
It is a coenzyme of decarboxylation reactions.
It is the coenzyme of redox reactions.
It is the coenzyme of carboxylation reactions

It is the coenzyme of acetylation reactions.

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.)

Electron transport would be unaffected but ATP synthesis would stop.
Electron transport would stop but ATP synthesis would be unaffected.
Both electron transport and ATP synthesis would stop.
Neither electron transport nor ATP synthesis would be affected.

Both electron transport and ATP synthesis would stop.

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?

The H+ gradient made from electron transport using NADH is located in a different part of the mitochondrion than the H+ gradient made using FADH2.
It takes more energy to make ATP from ADP and Pi using FADH2 than using NADH.
There is more NADH than FADH2 made for every glucose that enters cellular respiration.
Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.
FADH2 is made only in the citric acid cycle while NADH is made in glycolysis, acetyl CoA formation, and the citric acid cycle.

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

Under anaerobic conditions (a lack of oxygen), the conversion of pyruvate to acetyl CoA stops.
Which of these statements is the correct explanation for this observation?

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.
Oxygen is an input to acetyl CoA formation.
ATP is needed to convert pyruvate to acetyl CoA. Without oxygen, no ATP can be made in oxidative phosphorylation.
Oxygen is required to convert glucose to pyruvate in glycolysis. Without oxygen, no pyruvate can be made.

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.

Suppose that a cell's demand for ATP suddenly exceeds its supply of ATP from cellular respiration.
Which statement correctly describes how this increased demand would lead to an increased rate of ATP production?

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

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

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.
Glucose utilization would increase a little.
Glucose utilization would remain the same.
Glucose utilization would decrease a little.
Glucose utilization would decrease a lot.

Glucose utilization would increase a lot.

C6H12O6 (glucose) + 6 O2 → 6 CO2 + 6 H2O
Where is most of the water in this reaction produced?

in the Krebs cycle
during fermentation
in the electron transport chain
during glycolysis

in the electron transport chain

The energy of electron transport serves to move (translocate) protons to the outer mitochondrial compartment. How does this help the mitochondrion to produce energy?

The hydrogen ions (protons) are transferred to oxygen in an energy-releasing reaction.
The protons pick up electrons from the electron transport chain on their way through the inner mitochondrial membrane.
The translocation of protons sets up the electrochemical gradient that drives ATP synthesis in the mitochondria.
The protons receive electrons from the NAD+ and FAD that are accepted by electrons in glycolysis and the Krebs cycle.

The translocation of protons sets up the electrochemical gradient that drives ATP synthesis in the mitochondria.

The inner mitochondrial membrane normally _____.

contains an active transport pump that pumps protons into the inner mitochondrial compartment from the point of high concentration to a point of lower concentration
contains enzymes responsible for two of the chemical reactions that take place as part of glycolysis
is virtually impermeable to hydrogen ions (protons)
contains permease channels that allow small ions and water to pass readily through the membrane by simple diffusion

is virtually impermeable to hydrogen ions (protons)

Fatty acids usually have an even number of carbons in their structures. They are catabolized by a process called beta-oxidation. The end products of the metabolic pathway are acetyl groups of acetyl CoA molecules. What is the most likely fate of the acetyl groups?

They directly enter the Krebs cycle.
They directly enter the electron transport chain.
They directly enter the energy-yielding stages of glycolysis.
They are directly decarboxylated by pyruvate dehydrogenase.

They directly enter the Krebs cycle.

In muscle cells, fermentation produces _____.

carbon dioxide, ethanol, and NAD+
lactate and NAD+
lactate, NADH, and ATP
carbon dioxide, ethanol, NADH, and ATP
pyruvate

lactate and NAD+

In fermentation _____ is reduced and _____ is oxidized.

pyruvate ... NADH
lactate ... ethanol
NAD+ ... pyruvate
NADH ... lactate
lactate ... NADH

pyruvate ... NADH

Which molecule is metabolized in a cell to produce energy for performing work?

ADP
Phosphate
Glucose
ATP

Glucose

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

Electron transport chain
Glycolysis
Krebs cycle
Fermentation

Fermentation

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

Electron transport chain
Glycolysis
Krebs cycle
Fermentation

Glycolysis

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

Carbon dioxide
Water
NADH
ATP

Carbon dioxide

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

NADH and FADH2 donate their electrons to the chain.
The electron transport chain is the first step in cellular respiration.
Water is the last electron acceptor.
Electrons gain energy as they move down the chain.

NADH and FADH2 donate their electrons to the chain.

Which stage of glucose metabolism produces the most ATP?

Glycolysis
Krebs cycle
Electron transport and chemiosmosis
Fermentation of pyruvate to lactate

Electron transport and chemiosmosis

When ATP is hydrolyzed into ADP and inorganic phosphate, _____.

a large amount of energy is consumed
energy is required
the energy of the ATP molecule stays the same
a large amount of energy is released

a large amount of energy is released

When one molecule gains an electron from another, the molecule that received the electron has been _____.

oxidized
destroyed
redoxed
reduced

reduced

In cellular respiration, glucose is _____ and oxygen is _____.

produced, degraded
oxidized, reduced
reduced, oxidized
phosphorylated, dephosphorylated

oxidized, reduced

_____ is the three-carbon sugar that is produced as an end product of glycolysis.

Pyruvate
Fructose
Acetyl CoA
ADP

Pyruvate

A substrate-level phosphorylation occurs in the Krebs cycle when _____.

NAD+ is phosphorylated to NADH
oxaloacetate is phosphorylated
acetylation of oxaloacetate takes place
GDP is phosphorylated to produce GTP

GDP is phosphorylated to produce GTP

The enzyme phosphofructokinase is the major regulatory enzyme of glycolysis. It catalyzes _____.

the phosphorylation of ADP to ATP
the isomerization of glucose 6-phosphate to fructose 6-phosphate
the substrate-level phosphorylation reaction whereby phosphoenolpyruvate is converted to pyruvate
the phosphorylation of fructose 6-phosphate

the phosphorylation of fructose 6-phosphate

How do allosteric regulation and competitive inhibition compare?

Allosteric regulation involves binding of a regulatory molecule to the active site; in competitive inhibition a regulatory molecule binds to a different location.
Competitive inhibition involves binding of a regulatory molecule to the active site; in allosteric regulation a regulatory molecule binds to a different location.
Both involve binding of a regulatory molecule to a location other than the active site.
Both involve binding of a regulatory molecule to the active site.

Competitive inhibition involves binding of a regulatory molecule to the active site; in allosteric regulation a regulatory molecule binds to a different location.

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

O2 only
ATP and NADH only
CO2 only
pyruvate and ATP only
pyruvate, ATP, and NADH
ATP only
NADH only

pyruvate, ATP, and NADH

The chemiosmotic hypothesis is an important concept in our understanding of cellular metabolism in general because _____.

it explains how electron transport can fuel substrate-level phosphorylation
it explains the reduction of oxygen to water in the final steps of oxidative metabolism
it explains the sequence of the electron transport chain molecules
it explains how ATP is synthesized by a proton motive force

it explains how ATP is synthesized by a proton motive force

Why is ATP production during cellular respiration characterized as indirect?

Most of the ATP is produced during glucose oxidation, which occurs through a series of intermediate steps.
Electrons are not passed directly from NADH and FADH2 to O2 but indirectly through the ETC.
ATP is not produced directly by the ETC but instead via the proton gradient generated during electron transport through the ETC.
ATP is produced by enzymes indirectly associated with the ETC that perform substrate-level phosphorylation

ATP is not produced directly by the ETC but instead via the proton gradient generated during electron transport through the ETC.

Why are fermentation reactions important for cells?

They generate oxygen.
They regenerate NAD+ so that glycolysis can continue to operate.
They allow the cell to conserve oxygen for the Krebs cycle.
They produce alcohol which enhances the permeability of their mitochondrial membranes to proton translocation

They regenerate NAD+ so that glycolysis can continue to operate.

What would happen to NADH levels in a cell in the first few seconds after a drug has poisoned the enzyme that converts acetyl CoA to citrate?

NADH levels would decrease.
NADH levels would increase.
NADH levels would remain unchanged
None of the listed responses is correct.

NADH levels would decrease.

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