Chapter 8

Question 1

A metabolic pathway begins with a specific molecule, which is then altered in a series of defined steps, resulting in a certain product. Each step of the pathway is catalyzed by a specific enzyme.

Answer 1

True

Question 2

Catabolic pathways (breakdown pathways)

Answer 2

-Degradative processes
Metabolic pathways that release energy by breaking down complex molecules to simpler compounds.

Question 3

Anabolic pathways (bio synthetic pathways)

Answer 3

Consume energy to build complicated molecules from simpler ones

Question 4

Catabolic and anabolic pathways are the “downhill” and “uphill” avenues of the metabolic landscape.

Answer 4

True
Downhill reactions = Catabolic pathways
Uphill reactions = Anabolic pathways

Question 5

Bioenergetics

Answer 5

The study of how energy flows through living organisms

Question 6

Chemical energy

Answer 6

Refers to the potential energy available for release in a chemical reaction.

Question 7

Thermodynamics

Answer 7

The study of the energy transformations that occur in a collection of matter.

Question 8

First law of thermodynamics
Principle of conservation of energy

Answer 8

Energy can be transferred and transformed, but it cannot be created or destroyed.

Question 9

Entropy

Answer 9

A measure of disorder, or randomness.
The more randomly arranged a collection of matter is, the greater its entropy.

Question 10

Second law of thermodynamics

Answer 10

Every energy transfer or transformation increases the entropy of the universe.

Question 11

Spontaneous process (energetically favorable process)

Answer 11

If a given process, by itself, leads to an increase in entropy, that process can proceed without requiring an input of energy.

Question 12

A process that, considered on its own, leads to a decrease in entropy is said to be __________

Answer 12

Nonspontaneous

Question 13

Free energy (Gibbs free energy of a system)

Answer 13

-symbolized by the letter “G”
Is the portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell.

Question 14

Formula for ΔG

Answer 14

ΔG = ΔH — TΔS

Question 15

ΔH symbolizes…

Answer 15

The change in a systems enthalpy (in biological systems, equivalent to total energy)

Question 16

ΔS symbolizes…

Answer 16

Change in the system’s entropy

Question 17

T symbolizes

Answer 17

The absolute temperature in Kelvin (K) units

Question 18

K = •C + 273

Answer 18

True

Question 19

Only processes with a ______________ are spontaneous

Answer 19

negative ΔG

Question 20

Every spontaneous process decreases the system’s free energy, and processes that have a positive or zero ΔG are never spontaneous.

Answer 20

True

Question 21

A process is spontaneous and can perform work only when it is moving toward equilibrium.

Answer 21

True

Question 22

Exergonic reaction

Answer 22

Net release of free energy
ΔG is negative
-Occurs spontaneously

Question 23

Endergonic reaction

Answer 23

Absorbs free energy from its surroundings
-Is non spontaneous

Question 24

Chemical work

Answer 24

The pushing of endergonic reactions that would not occur spontaneously, such as the synthesis of polymers from monomers.

Question 25

Transport work

Answer 25

The pumping of substances across membranes against the direction of spontaneous movement.

Question 26

Mechanical work such as…

Answer 26

The beating of cilia, the contraction of muscle cells, and the movement of chromosomes during cellular reproduction.

Question 27

Energy coupling

Answer 27

The use of an exergonic process to drive an endergonic one.

Question 28

Phosphorylation

Answer 28

The transfer of a phosphate group from ATP to some other molecule

Question 29

Phosphorylated intermediate

Answer 29

The recipient molecule with the phosphate group covalently bonded to it

Question 30

To reach the contorted state where bonds can change, reactant molecules must absorb energy from their surroundings.

Answer 30

True

Question 31

Activation energy (free energy of activation)

Answer 31

The energy required to contort the reactant molecules so the bonds can break.

Question 32

Transition state

Answer 32

When the molecules have absorbed enough energy for the bonds to break.

Question 33

The activation energy provides a barrier that determines the rate of the reaction

Answer 33

True

Question 34

An enzyme catalyzes a reaction by…

Answer 34

Lowering the activation energy barrier

Question 35

Substrate

Answer 35

The reaction an enzyme acts on

Question 36

Active site

Answer 36

Region on the surface of the enzyme where catalysis occurs.

Question 37

Cofactors

Answer 37

Nonprotein enzyme helpers

Question 38

Coenzyme

Answer 38

A cofactor that is an organic molecule.

Question 39

Competitive inhibitors

Answer 39

“Mimics” that reduce the productivity of enzymes by blocking substrates from entering active sites.

Question 40

Noncompetitive inhibitors

Answer 40

Bind to another part of the enzyme, which changes its shape in such a way that the active site becomes less effective at catalyzing.

Question 41

Allosteric regulation

Answer 41

Is the term used to describe any case in which a protein’s function at one site is affected by the bonding of a regulatory molecule to a separate site.

Question 42

Feedback inhibition

Answer 42

A metabolic pathway is halted by the inhibitory binding of its end product to an enzyme that acts early in the pathway.