Biochemistry Chapter 2: Enzymes (4 Stars)

Question 1

______ are biological catalysts that are unchanged by the reactions they catalyze and are reusable.

Answer 1

Enzymes

Question 2

Each enzyme catalyzes a single reaction or type of reaction with high ______

Answer 2

specificity.

Question 3

______ catalyze oxidation–reduction reactions that involve the transfer of electrons.

Answer 3

Oxidoreductases

Question 4

______ move a functional group from one molecule to another molecule.

Answer 4

Transferases

Question 5

_______ catalyze cleavage with the addition of water.

Answer 5

Hydrolases

Question 6

______ catalyze cleavage without the addition of water and without the transfer of electrons. The reverse reaction (synthesis) is often more important biologically.

Answer 6

Lyases

Question 7

______ catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers.

Answer 7

Isomerases

Question 8

_____ are responsible for joining two large biomolecules, often of the same type.

Answer 8

Ligases

Question 9

_______ reactions release energy; ΔG is negative.

Answer 9

Exergonic

Question 10

Enzymes _____ the activation energy necessary for biological reactions.

Answer 10

lower

Question 11

Enzymes do not alter the free energy (ΔG) or enthalpy (ΔH) change that accompanies the reaction nor the final equilibrium position; rather, they change the rate _____ at which equilibrium is reached.

Answer 11

(kinetics)

Question 12

Enzymes act by stabilizing the _____ state, providing a favorable microenvironment, or bonding with the substrate molecules.

Answer 12

transition

Question 13

Enzymes have ______ , which is the site of catalysis.

Answer 13

active site

Question 14

______ to the active site is explained by the lock and key theory or the induced fit model.

Answer 14

Binding

Question 15

_______ hypothesizes that the enzyme and substrate are exactly complementary.

Answer 15

The lock and key theory

Question 16

__________ hypothesizes that the enzyme and substrate undergo conformational changes to interact fully.

Answer 16

The induced fit model

Question 17

Some enzymes require metal ____ cofactors or small organic coenzymes to be active.

Answer 17

cation

Question 18

Enzymes experience ______ kinetics: as substrate concentration increases, the reaction rate does as well until a maximum value is reached.

Answer 18

saturation

Question 19

Michaelis–Menten and Lineweaver–Burk plots represent this relationship as a _____and line, respectively.

Answer 19

hyperbola

Question 20

______ can be compared on the basis of their Km and vmax values.

Answer 20

Enzymes

Question 21

______ enzymes display a sigmoidal curve because of the change in activity with substrate binding.

Answer 21

Cooperative

Question 22

Temperature and pH affect an _______ activity in vivo; changes in temperature and pH can result in denaturing of the enzyme and loss of activity due to loss of secondary, tertiary, or, if present, quaternary structure.

Answer 22

enzyme’s

Question 23

In vitro, ______ can impact the action of enzymes.

Answer 23

salinity

Question 24

Enzyme pathways are highly ______ and subject to inhibition and activation.

Answer 24

regulated

Question 25

__________ is a regulatory mechanism whereby the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway.

Answer 25

Feedback inhibition

Question 26

_________ is characterized by the ability to replace the inhibitor with a compound of greater affinity or to remove it using mild laboratory treatment.

Answer 26

Reversible inhibition

Question 27

_________ results when the inhibitor is similar to the substrate and binds at the active site. Competitive inhibition can be overcome by adding more substrate. vmax is unchanged, Km increases.

Answer 27

Competitive inhibition

Question 28

___________ results when the inhibitor binds with equal affinity to the enzyme and the enzyme–substrate complex. vmax is decreased, Km is unchanged.

Answer 28

Noncompetitive inhibition

Question 29

____________ results when the inhibitor binds with unequal affinity to the enzyme and the enzyme–substrate complex. vmax is decreased, Km is increased or decreased depending on if the inhibitor has higher affinity for the enzyme or enzyme–substrate complex.

Answer 29

Mixed inhibition

Question 30

__________ results when the inhibitor binds only with the enzyme–substrate complex. Km and vmax both decrease.

Answer 30

Uncompetitive inhibition

Question 31

___________ alters the enzyme in such a way that the active site is unavailable for a prolonged duration or permanently; new enzyme molecules must be synthesized for the reaction to occur again.

Answer 31

Irreversible inhibition

Question 32

Regulatory enzymes can experience activation as well as ______

Answer 32

inhibition.

Question 33

Allosteric sites can be occupied by _____, which increase either affinity or enzymatic turnover.

Answer 33

activators

Question 34

Phosphorylation (covalent modification with phosphate) or ________ (covalent modification with carbohydrate) can alter the activity or selectivity of enzymes.

Answer 34

glycosylation

Question 35

______ are secreted in an inactive form and are activated by cleavage

Answer 35

Zymogens