Quiz 4

Question 1

Biological evolution of life on Earth, from simple prokaryote-like cells to large, multicellular eukaryotic organisms..
a) has occurred in accordance with the laws of thermodynamics
b) has caused an increase in entropy of the planet
c) has occurred in accordance with the laws of thermodynamics, by expending Earths energy resources and causing an increase in the entropy of the planet

Answer 1

a) has occurred in accordance with the laws of thermodynamics

Question 2

Which of the following statements regarding enzymes is true?
a) Enzymes increase the rate of a reaction by making the reaction more exergonic.
b) Enzymes increase the rate of a reaction by reducing the rate of reverse reactions.
c) Enzymes increase the rate of a reaction by lowering the activation energy barrier.
d) Enzymes change the equilibrium point of the reactions they catalyze.
e) Enzymes make the rate of a reaction independent of substrate concentrations.

Answer 2

c) Enzymes increase the rate of a reaction by lowering the activation energy barrier.

Question 3

A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because..
a) the hydrolysis of starch to sugar is endergonic
b) the starch solution has less free energy than the sugar solution.
c) starch hydrolysis is nonspontaneous
d) starch cannot be hydrolyzed in the presence of so much water
e) the activation energy barrier for this reaction cannot be surmounted

Answer 3

e) the activation energy barrier for this reaction cannot be surmounted

Question 4

Which of the following statements is true about enzyme-catalyzed reactions?
a) The free energy change of the reaction is opposite from the reaction that occurs in the absence of the enzyme.
b) The reaction is faster than the same reaction in the absence of the enzyme.
c) The reaction always goes in the direction toward chemical equilibrium
d) Enzyme-catalyzed reactions require energy to activate the enzyme.
e) Enzyme-catalyzed reactions release more free energy than noncatalyzed reactions.

Answer 4

b) The reaction is faster than the same reaction in the absence of the enzyme.

Question 5

Reactants capable of interacting to form products in a chemical rxn must first overcome a thermodynamic barrier known as the rxns _____?
a) free-energy content
b) activation energy
c) entropy
d) endothermic lvl

Answer 5

b) activation energy

Question 6

Energy coupling occurs when what?

Answer 6

an exergonic rxn drives an endergonic rxn

Question 7

Living organisms increase in complexity as they grow, resulting in a decrease in the entropy of an organism. How does this relate to the second law of thermodynamics?
a) Life obeys the second law of thermodynamics because the decrease in entropy as the organism grows is exactly balanced by an increase in the entropy of the universe.
b) Living organisms do not obey the second law of thermodynamics, which states that entropy must increase with time.
c) Living organisms do not follow the laws of thermodynamics.
d) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy
e) associated with their growth
Living organisms are able to transform energy into entropy.

Answer 7

d) As a consequence of growing, organisms cause a greater increase in entropy in their environment than the decrease in entropy

Question 8

Where are the proteins of the electron transport chain located?
a) cytosol
b) mitochondrial outer membrane
c) mitochondrial inner membrane
d) mitochondrial matrix

Answer 8

c) mitochondrial inner membrane

Question 9

It is possible to prepare vesicles from portions of the inner mitochondrial membrane. Which one of the following processes could still be carried on by this isolated inner membrane?
a) reduction of NAD+
b) both the citric acid cycle and oxidative phosphorylation
c) the citric acid cycle
d) glycolysis and fermentation
e) oxidative phosphorylation

Answer 9

e) oxidative phosphorylation

Question 10

In prokaryotes, the respiratory electron transport chain is located…?
a) in the cytoplasm.
b) in the mitochondrial inner membrane.
c) in the mitochondrial outer membrane.
d) in the bacterial outer membrane.
e) in the plasma membrane.

Answer 10

e) in the plasma membrane.

Question 11

How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?
a) two
b) four
c) six
d) eight
e) ten

Answer 11

a) two

Question 12

One function of both alcohol fermentation and lactic acid fermentation is to…?
a) reduce NAD+ to NADH
b) reduce FAD+ to FADH2
c) reduce FADH2 to FAD+
d) oxidize NADH to NAD+

Answer 12

d) oxidize NADH to NAD+

Question 13

Carbon dioxide is released during which of the following stages of cellular respiration?
a) oxidative phosphorylation and fermentation
b) the citric acid cycle and oxidative phosphorylation
c) oxidation of pyruvate to acetyl CoA and the citric acid cycle
d) fermentation and glycolysis
e) glycolysis and the oxidation of pyruvate to acetyl CoA

Answer 13

c) oxidation of pyruvate to acetyl CoA and the citric acid cycle

Question 14

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 the liver cell to have fewer mitochondria.
b) It increases the surface for substrate-level phosphorylation.
c) It allows for an increased rate of glycolysis.
d) It allows for an increased rate of the citric acid cycle
e) It increases the surface for oxidative phosphorylation

Answer 14

e) It increases the surface for oxidative phosphorylation

Question 15

What is the first law of thermodynamics?

Answer 15

Energy cannot be created or destroyed.

Question 16

Whenever energy is transformed, there is always an increase in the..?

a) free energy of the system.
b) entropy of the universe.
c) entropy of the system.
d) free energy of the universe.
e) enthalpy of the universe.

Answer 16

b) entropy of the universe

Question 17

Inside an active mitochondrion, most electrons follow which pathway?

a) citric acid cycle → FADH2 → electron transport chain → ATP
b) citric acid cycle → NADH → electron transport chain → oxygen
c) electron transport chain → citric acid cycle → ATP → oxygen
d) pyruvate → citric acid cycle → ATP → NADH → oxygen
e) glycolysis → NADH → oxidative phosphorylation → ATP → oxygen

Answer 17

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

Question 18

An electron loses potential energy when it does what?

Answer 18

shifts to a more electronegative atom

Question 19

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by..?

a) cellular metabolic reactions that create or destroy ions.
b) passive diffusion across the plasma membrane.
c) cotransport proteins.
d) ion channels.
e) carrier proteins.

Answer 19

c) cotransport proteins.

Question 20

Which of the following statements is representative of the second law of thermodynamics?

a) Conversion of energy from one form to another is always accompanied by some gain of free energy.
b) Heat represents a form of energy that can be used by most organisms to do work.
c) Without an input of energy, organisms would tend toward decreasing entropy.
d) Cells require a constant input of energy to maintain their high level of organization.

Answer 20

d) Cells require a constant input of energy to maintain their high level of organization.

Question 21

Chemical equilibrium is relatively rare in living cells. which of the following could be an example of a reaction at chemical equilibrium in a cell?

a) a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium
b) a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway
c) an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment
d) a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell’s surroundings

Answer 21

b) a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway

Question 22

When 10 000 moleucles of ATP are hydrolyzed to AD and inorganic phosphate in a test tube, about twice as much heat is liberated as when a the same amount of ATP is hydrolyzed in a cell. Which of the following is the best explanation for this observation?

a) Cells are less efficient at heat production than are nonliving systems.
b) They hydrolysis of ATP in a cell produces different chemical products than does the reaction in a test tube.
c) Reactant and product concentrations in the test tube are different from those in the cell.
d) The reaction in cells must by catalyzed by enzymes, but the reaction in a test tube does not need enzymes.

Answer 22

b) They hydrolysis of ATP in a cell produces different chemical products than does the reaction in a test tube.

Question 23

The active site of an enzyme is the region that…?

a) binds allosteric regulators to the enzyme
b) is involved in the catalytic reaction of the enzyme.
c) binds noncompetitive inhibitors of the enzyme.
d) is inhibited by the presence of a coenzyme or a cofactor.

Answer 23

b) is involved in the catalytic reaction of the enzyme.

Question 24

The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction..?

a) loses electrons and loses potential energy.
b) gains electrons and gains potential energy.
c) gains electrons and loses potential energy.
d) loses electrons and gains potential energy.

Answer 24

a) loses electrons and loses potential energy.

Question 25

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) Without NAD+, glycolysis can still function.

Answer 25

a) NAD+ is reduced to NADH during glycolysis, pyruvate oxidation,
and the citric acid cycle.

Question 26

What intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (carbon dioxide) from one molecule of pyruvate?

Answer 26

Acetyl CoA

Question 27

The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is..?

a) oxidation of glucose to carbon dioxide and water.
b) the thermodynamically favourable 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.

Answer 27

d) the proton-motive force across the inner mitochondrial membrane.

Question 28

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

Answer 28

b) substrate-level phosphorylation

Question 29

What is the purpose of beta oxidation in respiration?
a) oxidation of glucose
b) oxidation of pyruvate
c) feedback regulation
d) breakdown of fatty acids

Answer 29

d) breakdown of fatty acids

Question 30

Which of the following is (are) true for anabolic pathways?

a) They release energy as they degrade polymers to monomers.
b) They consume energy to decrease the entropy of the organism and its environment.
c) They do not depend on enzymes
d) They consume energy to build up polymers from monomers.
e) They are usually highly spontaneous chemical reactions.

Answer 30

d) They consume energy to build up polymers from monomers.

Question 31

How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?

a) by decreasing the activation energy of the reaction
b) by acting as a coenzyme for the reaction
c) by changing the shape of the enzyme’s active site
d) by binding at the active site of the enzyme
e) by changing the free energy change of the reaction

Answer 31

c) by changing the shape of the enzyme’s active site

Question 32

Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?

a) cessation of cellular protein synthesis
b) connecting enzymes into large aggregates
c) localization of enzymes into specific organelles or membranes
d) hydrophobic interactions
e) exporting enzymes out of the cell

Answer 32

c) localization of enzymes into specific organelles or membranes

Question 33

A molecule that is phosphorylated

a) has an increased chemical potential energy; it is primed to do cellular work.
b) has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate.
c) has a decreased chemical reactivity; it is less likely to provide energy for cellular work.
d) has less energy than before its phosphorylation and therefore less energy for cellular work.
e) has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate.

Answer 33

a) has an increased chemical potential energy; it is primed to do cellular work.

Question 34

Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

a) The oxidation of organic compounds can be used to make ATP.
b) The covalent bonds in organic molecules and molecular oxygen have more kinetic energy than the covalent bonds in water and carbon dioxide.
c) The covalent bond in O2 is unstable and easily broken by electrons from organic molecules.
d) The electrons have a higher potential energy when associated with water and CO2 than they do in organic compounds.
e) 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).

Answer 34

e) 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).

Question 35

What is the term for metabolic pathways that release stored energy by breaking down complex molecules?

a) catabolic pathways
b) anabolic pathways

Answer 35

a) catabolic pathways

Question 36

Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?

a) in cells that are storing glucose only
b) in photosynthesizing cells in the light and in other tissues in the dark
c) in nonphotosynthesizing cells only
d) in all cells all the time
e) in photosynthetic cells in the light, while photosynthesis occurs concurrently

Answer 36

d) in all cells all the time

Question 37

Starting with one molecule of glucose, the energy-containing products of glycolysis are

a) 2 NAD+, 2 pyruvate, and 2 ATP.
b) 6 CO2, 30 ATP, and 2 pyruvate.
c) 2 NADH, 2 pyruvate, and 2 ATP.
d) 2 FADH2, 2 pyruvate, and 4 ATP.
e) 6 CO2, 2 ATP, and 2 pyruvate.

Answer 37

c) 2 NADH, 2 pyruvate, and 2 ATP.

Question 38

It is possible to prepare vesicles from portions of the inner mitochondrial membrane. Which one of the following processes could still be carried on by this isolated inner membrane?

a) reduction of NAD+
b) both the citric acid cycle and oxidative phosphorylation
c) the citric acid cycle
d) glycolysis and fermentation
e) oxidative phosphorylation

Answer 38

e) oxidative phosphorylation

Question 39

When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?

a) The phosphate may be incorporated into any molecule that contains phosphate.
b) The phosphate can be added to water and excreted as a liquid.
c) The phosphate can only be used to regenerate more ATP.
d) The phosphate is released as an excretory waste.
e) It enters the nucleus to affect gene expression.

Answer 39

a) The phosphate may be incorporated into any molecule that contains phosphate.

Question 40

Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?

a) catabolism
b) catalysis
c) dehydration
d) metabolism
e) anabolism

Answer 40

a) catabolism

Question 41

Which of the following statements is true concerning catabolic pathways?

a) They are endergonic.
b) They supply energy, primarily in the form of ATP, for the cell’s work.
c) They build up complex molecules such as protein from simpler compounds.
d) They combine molecules into more energy-rich molecules.
e) They are spontaneous and do not need enzyme catalysis.

Answer 41

b) They supply energy, primarily in the form of ATP, for the cell’s work.

Question 42

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as…

a) allosteric inhibition.
b) metabolic inhibition.
c) reversible inhibition.
d) feedback inhibition.
e) noncooperative inhibition.

Answer 42

d) feedback inhibition.

Question 43

Where does glycolysis take place in eukaryotic cells?

a) cytosol
b) mitochondrial inner membrane
c) mitochondrial outer membrane
d) mitochondrial matrix
e) mitochondrial intermembrane space

Answer 43

a) cytosol

Question 44

During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?

a) pyruvate (C3H3O3-)
b) glucose (C6H12O6)
c) molecular oxygen (O2)
d) lactate (C3H5O3-)
e) carbon dioxide (CO2)

Answer 44

c) molecular oxygen (O2)

Question 45

During cellular respiration, acetyl CoA accumulates in which location?

a) mitochondrial inner membrane
b) mitochondrial matrix
c) cytosol
d) mitochondrial intermembrane space
e) mitochondrial outer membrane

Answer 45

b) mitochondrial matrix

Question 46

Where is ATP synthase located in the mitochondrion?

a) inner membrane
b) outer membrane
c) electron transport chain
d) mitochondrial matrix
e) cytosol

Answer 46

a) inner membrane

Question 47

Which of the following is a major cause of the size limits for certain types of cells?

a) limitation on the strength and integrity of the plasma membrane as cell size increases
b) the difference in plasma membranes between prokaryotes and eukaryotes
c) rigid cell walls that limit cell size expansion
d) evolutionary progression in cell size; more primitive cells have smaller sizes
e) the need for a surface area of sufficient area to support the cell’s metabolic needs

Answer 47

e) the need for a surface area of sufficient area to support the cell’s metabolic needs

Question 48

When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the..?

a) reduction of NAD+.
b) lowering of pH in the mitochondrial matrix.
c) creation of a proton-motive force.
d) formation of ATP.
e) restoration of the Na+/K+ balance across the membrane.

Answer 48

c) creation of a proton-motive force.

Question 49

Which of the following statements describes the results of this reaction?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy

a) O2 is reduced and CO2 is oxidized.
b) C6H12O6 is oxidized and O2 is reduced.
c) C6H12O6 is reduced and CO2 is oxidized.
d) CO2 is reduced and O2 is oxidized.
e) O2 is oxidized and H2O is reduced.

Answer 49

b) C6H12O6 is oxidized and O2 is reduced.

Question 50

A reaction that absorbs free energy from its surroundings is a(n) ________ reaction.

a) endergonic
b) exergonic
c) spontaneous
d) exothermic
e) endothermic

Answer 50

a) endergonic

..if you chose exergonic remember that the rxn is then spontaneous and energy is RELEASED not absorbed.

Question 51

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the reactions of glycolysis?

a) 10%
b) 2%
c) 100%
d) 0%
e) 38%

Answer 51

c) 100%

Question 52

During respiration, energy flows in the following sequence.

a) glucose → NADH → electron transport → oxygen
b) pyruvate → acetyl-CoA → electron transport → water
c) glucose → electron transport → NADH → proton-motive force → ATP
d) glucose → NADH → electron transport → proton-motive force → ATP
e) glucose → pyruvate → acetyl-CoA → CO2

Answer 52

d) glucose → NADH → electron transport → proton-motive force → ATP

Question 53

Which of the following is true of metabolism in its entirety in all organisms?

a) Metabolism depends on a constant supply of energy from food.
b) Metabolism consists of all the energy transformation reactions in an organism.
c) Metabolism depends on an organism’s adequate hydration.
d) Metabolism manages the increase of entropy in an organism.
e) Metabolism uses all of an organism’s resources.

Answer 53

b) Metabolism consists of all the energy transformation reactions in an organism.