Deck 5: The Flow of Energy

Question 1

The second law of thermodynamics states that if no energy enters or leaves the system under study, the potential energy of the final state will be______ the potential energy of the initial state.

A)equal to
B)greater than or equal to
C)greater than
D)less than
E)less than or equal to

Answer 1

D

Question 2

ΔG refers to the change in ______ of the system.

A)the total heat content
B)free energy
C)entropy
D)enthalpy
E)the randomness

Answer 2

B

Question 3

Of the total solar energy that reaches the Earth, ______ percent is captured by the cells of photosynthetic organisms.

A)about 50
B)about 20
C)about 10
D)about 5
E)less than 1

Answer 3

E

Question 4

Which of the following statements about living cells is FALSE?

A)They expend energy to maintain order.
B)They are at equilibrium with their surroundings.
C)They are open systems.
D)They transform energy.
E)As they transform energy, they dissipate heat.

Question 5

During the oxidation of glucose in the cell, most of the energy is released:

A)all at once.
B)in small amounts.
C)via mechanisms that require many kinds of molecules.
D)via mechanisms that result in high temperatures.
E)in a way that requires the input of 686 kilocalories of energy.

Question 6

Glucose + oxygen → carbon dioxide + water

A)Glucose
B)Oxygen
C)Carbon dioxide
D)Water
E)Carbon dioxide and water are reduced.

Question 7

The energy of a system is defined as:

A)the amount of caloric present.
B)the amount of ATP present.
C)its capacity to do work.
D)the sum total of its chemical bonds.
E)the speed at which its atoms and molecules move.

Question 8

The second law of thermodynamics states that all naturally occurring processes:

A)are exothermic.
B)are endothermic.
C)are exergonic.
D)are endergonic.
E)proceed with an increase in entropy.

Question 9

The first law of thermodynamics states that the total energy of a system and its surroundings after an energy conversion is ______ the total energy before the conversion.

A)equal to
B)greater than or equal to
C)greater than
D)less than
E)less than or equal to

Question 10

Which of the following is NOT an example of potential energy?

A)A charged flashlight battery
B)A boulder at the top of a hill
C)A tank of gasoline
D)Water at the bottom of a waterfall
E)An apple on a branch
PAGE 66 Chapter 5 The Flow of Energy

Question 11

According to the first law of thermodynamics, the total energy of ______ is ______.

A)a system; constant
B)a system; changeable
C)the surroundings; constant
D)the universe; constant
E)the universe; changeable

Question 12

ΔH refers to the:

A)heat released in an exergonic reaction.
B)heat released in an endergonic reaction.
C)change in enthalpy.
D)change in entropy.
E)exact change in potential energy.

Question 13

Oxidation is defined as the:

A)loss of electrons.
B)loss of protons.
C)loss of electrons and protons.
D)gain of electrons.
E)gain of protons.

Question 14

An exergonic reaction:

A)is a reaction in which the potential energy of the final state is less than that of the initial state.
B)does not take place spontaneously.
C)requires an input of energy from the outside.
D)has a positive free-energy change.
E)has a positive ΔG value.

Question 15

One way of stating the second law of thermodynamics is:

A)although energy can be changed from one form to another, it can be neither created nor destroyed.
B)the entropy of the universe is increasing.
C)free energy is equal to the total potential energy minus the entropy.
D)enthalpy is the total potential energy of a system.
E)the activation energy of a reaction is always positive.

Question 16

The first law of thermodynamics states that:

A)all natural processes proceed in such a direction that the disorder of the universe increases.
B)the activation energy of chemical reactions is raised by enzymes.
C)energy can be changed from one form to another, but it cannot be created or destroyed.
D)ΔG = ΔH - TΔS.
E)ATP is the energy currency of the cell.

Question 17

In biological reactions, when a molecule is oxidized it ______ an electron and a(n) ______.

A)loses; proton
B)gains; proton
C)loses; oxygen atom
D)gains; oxygen atom
E)loses; neutron

Question 18

In all naturally occurring processes:

A)ΔH is positive.
B)ΔH is negative.
C)ΔS is positive.
D)ΔS is negative.
E)ΔG is negative.

Question 19

Which of the following equations relating enthalpy, entropy, and free energy is correct?

A)ΔS = ΔH - T ΔG
B)ΔH = ΔG - T ΔS
C)ΔS = ΔG + T ΔH
D)ΔG = ΔH - T ΔS
E)ΔG = ΔH + T ΔS

Question 20

Entropy refers to the ______ of a system.

A)heat content
B)free energy
C)potential energy
D)disorder or randomness
E)kinetic energy

Question 21

Which of the following statements about metabolic pathways is FALSE?

A)The enzymes of some pathways are segregated inside specific organelles.
B)The enzymes of some pathways are embedded in specific membranes.
C)The enzymes of most pathways allow intermediate products to accumulate.
D)Exergonic reactions in the pathway will pull forward preceding reactions.
E)The products from exergonic reactions will push along subsequent reactions.

Question 22

The general name for a nonprotein component required by some enzymes is a:

A)metal ion.
B)cofactor.
C)substrate.
D)prosthetic group.
E)coenzyme.

Question 23

Denaturation of an enzyme refers to the:

A)proper arrangement of the enzyme in a metabolic pathway.
B)improper arrangement of the enzyme in a metabolic pathway.
C)loss of the enzyme's proper shape.
D)formation of the enzyme's proper shape.
E)formation of a new isozyme for that enzyme.

Question 24

In an allosteric enzyme, the substrate binds at the ______ site and the regulatory substance binds at the ______ site.

A)active; effector
B)effector; active
C)active; inhibitor
D)inhibitor; active
E)inhibitor; effector

Question 25

A substrate binds to its enzyme at a location called the ______ site.

A)coenzyme
B)substrate
C)active
D)polypeptide
E)cofactor

Question 26

ATP + H₂O → ADP + phosphate

A)phosphorylase
B)ATPase
C)ADPase
D)kinase
E)phosphatase

Question 27

An enzyme:

A)is typically effective only in large amounts.
B)is a type of carbohydrate.
C)raises the activation energy of its reaction.
D)functions as a catalyst.
E)is permanently altered during the course of its reaction.

Question 28

Isozymes are:

A)RNA molecules that catalyze metabolic reactions.
B)identical coenzymes that require different metal ions.
C)identical coenzymes located in different parts of the cell.
D)different enzymes that catalyze identical reactions.
E)identical enzymes that catalyze different reactions.

Question 29

Most enzymes are:

A)RNA molecules.
B)proteins.
C)carbohydrates.
D)lipids.
E)DNA molecules.

Question 30

Most enzymes that catalyze phosphorylation reactions require ______ as a cofactor.

A)NAD⁺
B)Mg²⁺
C)Ca²⁺
D)AMP
E)an iron-sulfur cluster

Question 31

In feedback inhibition, the ______ enzyme in a metabolic pathway is inhibited by the ___________.

A)last; first substrate
B)last; end product
C)first; cofactor
D)first; first substrate
E)first; end product

Question 32

A regulatory enzyme in a metabolic pathway is most likely to be the:

A)last enzyme in the pathway.
B)first enzyme in the pathway.
C)enzyme that catalyzes the fastest reaction in the pathway.
D)enyzme that binds its coenzyme the fastest.
E)enzyme that lacks an effector site.

Question 33

In a NAD+ molecule, a pyrophosphate bridge joins:

A)two nicotinamide molecules.
B)two adenine molecules.
C)one ribose molecule with one nicotinamide molecule.
D)two ribose molecules.
E)one ribose molecule with one adenine molecule.

Question 34

Which of the following is NOT a component of an ATP molecule?

A)adenine
B)a pyrophosphate bridge
C)phosphate groups
D)a phosphoanhydride bond
E)ribose

Question 35

In an ATP molecule, phosphoanhydride bonds link:

A)adenine to ribose.
B)adenine to a phosphate group.
C)the phosphate groups together.
D)ribose to a phosphate group.
E)the ribose groups together.

Question 36

The vitamin niacin is part of the ______ molecule.

A)ferredoxin
B)iron-sulfur
C)pyridoxal phosphate
D)pyrophosphate
E)NAD⁺

Question 37

As the temperature increases, the rate of an enzyme-catalyzed reaction usually:

A)increases constantly.
B)increases up to a point, then decreases.
C)decreases constantly.
D)decreases to a point, then increases.
E)increases, then decreases, then increases again.

Question 38

Which of the following statements concerning the effect of pH on enzyme activity is FALSE?

A)Enzyme shape changes as the pH changes.
B)The pH affects positively-charged amino acids.
C)The pH affects negatively-charged amino acids.
D)The binding capacity of an enzyme is affected by pH.
E)Enzymes are always present at their pH optimum.

Question 39

A negatively charged portion of a substrate molecule would most likely fit into a ______ region of its enzyme's active site.

A)positively charged
B)negatively charged
C)hydrophilic
D)hydrophobic
E)polar

Question 40

Which statement about the reaction ATP + H₂O → ADP + phosphate is FALSE?

A)It is catalyzed by an ATPase.
B)It releases about 7.3 kilocalories of energy per mole.
C)It involves the breaking of phosphoanhydride bonds.
D)The reactants are more stable than the products.
E)It is exergonic.

Question 41

Picking up clothes from the floor and hanging them in a closet results in an increase in entropy.

Question 42

When an atom is reduced, it loses electrons.

Question 43

A principal factor regulating enzyme activity in cells is the amount of substrate available.

Question 44

Which of the following statements about sucrose synthesis is FALSE?

A)Under standard thermodynamic conditions sucrose synthesis is endergonic.
B)In the cell, sucrose synthesis is endergonic.
C)In the cell, sucrose synthesis involves the phosphorylation of glucose.
D)In the cell, sucrose synthesis involves the phosphorylation of fructose.
E)In the cell, sucrose synthesis is coupled with ATP hydrolysis.
True-False Questions

Question 45

The overall charge in energy that determines the course of a chemical reaction is the free-energy charge, ΔG.

Question 46

When energy is changed from one form to another, the total energy after the change is equal to the total energy before the change.

Question 47

A metal ion can be a cofactor.

Question 48

A nucleotide is composed of a nucleoside plus a phosphate group.

Question 49

An endergonic reaction is one that releases energy.

Question 50

All enzymes are proteins.

Question 51

A coenzyme is type of protein.

Question 52

Plants, like humans, are unable to synthesize all of their required vitamins.

Question 53

When an enzyme is denatured it loses its shape.

Question 54

The heat released in the exhaust of an engine can produce work.

Question 55

In a metabolic pathway, there is little accumulation of intermediate products.

Question 56

The relationship between changes in free energy, enthalpy, and entropy that occur during a reaction can be expressed by the equation: ΔG = ΔH + T ΔS.

Question 57

Enzymes function by raising the activation energy of specific reactions.

Question 58

Oxidation and reduction always take place simultaneously.

Question 59

Which of the following is a phosphorylation reaction catalyzed by a kinase in plant cells?

A)ATP + glucose → glucose phosphate + ADP
B)Fructose phosphate + ADP → fructose + ATP
C)Glucose phosphate + ADP → glucose + ATP
D)ATP + H₂O → ADP + phosphate
E)ADP + phosphate → ATP + H₂O

Question 60

An enzyme binds with its substrate at the active site.

Question 61

An ATP molecule contains at least one pyrophosphate bridge.

Question 62

pH affects the rate of enzyme-catalyzed reactions by altering the charge on the enzyme and/or substrate(s).

Question 63

An ATP molecule contains at least one phosphoester bond.

Question 64

For most enzyme catalyzed reactions, the rate approximately doubles for each 5C increase in temperature.

Question 65

A coupled reaction is one in which an endergonic reaction is driven by an exergonic reaction.

Question 66

In an allosteric enzyme, the substrate binds to the effector site.