Enzymes

Question 1

What are the major six classes of enzymes?

Answer 1

LIL HOT
Lipase
Isomerase
Lyase
Hydrolase
Oxidoreductase
Transferase

Question 2

Function of Oxidoreductases; and important info

Answer 2

catalyze oxidation-reduction reactions, often have a cofactor that acts like an electron transporter like NAD+ and NADP+.
The electron donor is known as the reductant
the electron acceptor is known as the oxidant

Question 3

Function of Transferases; and important info

Answer 3

catalyze the movement of a functional group from one molecule to another. Kinases for example catalyze the transfer of a phosphate group like ATP to another molecule

Question 4

Function of Hydrolases; and important info

Answer 4

catalyze the breaking of a compound into two molecules using water. phosphatase cleaves a phosphate group from another molecule

Question 5

Function of Lyases; and important info

Answer 5

catalyze the cleavage of a single molecule into two products. do not require water. reversible function is referred to as a synthase

Question 6

Function of Isomerases; and important info

Answer 6

catalyze the rearrangement of bonds within a molecule. can catalyze reactions between stereoisomers as well as constitutional isomers

Question 7

Function of ligases; and important info

Answer 7

catalyze addition or synthesis reactions. generally between larger and similar molecules. often require ATP.

Question 8

Thermodynamically enzymes work by?

Answer 8

lowering the transition state of reactions or lowering the activation energy

Question 9

A very important characteristic of enzymes is that they do not alter the overall _ for a reaction, nor do that change the _ of a reaction

Answer 9

free energy

equilibrium

Question 10

What is a substrate

Answer 10

a molecule which an enzyme acts on

Question 11

What is an active site

Answer 11

the location within the enzyme where the substrate is held during the chemical reaction

Question 12

What is lock and key theory

Answer 12

suggests that the enzymes active site (lock) is already in the appropriate conformation for the substrate (key)

Question 13

What is the induced fit model

Answer 13

The substrate has induced a change in the shape of the enzyme

Question 14

What are prosthetic groups

Answer 14

tightly bound cofactors that are necessary for enzyme function

Question 15

What is the difference between apoenzymes and holoenzymes

Answer 15

apoenzymes= enzymes without cofactors
holoenzymes= enzymes containing cofactors

Question 16

Enzyme saturation refers to

Answer 16

once the reaction will no longer go any faster

Question 17

The michaelis-Menten equation

Answer 17

v= vmax [S] / Km + [S}

Question 18

When the reaction rate is equal to half of vmax Km =?

Answer 18

Km = [S]

Question 19

What is the Hill’s coefficient

Answer 19

quantifies cooperativity of enzymes

Question 20

If the Hill’s coefficient >1. what type of binding

Answer 20

positively cooperative binding is occurring, after one ligand is bound the affinity of the enzyme for further ligands increases

Question 21

If the Hill’s coefficient <1. what type of binding

Answer 21

negatively cooperative binding is occurring, after one ligand is bound the affinity of the enzyme for further ligands decreases

Question 22

If the Hill’s coefficient =1. what type of binding

Answer 22

the enzyme does not exhibit cooperative binding

Question 23

optimum temperature for enzymes in the human body is

Answer 23

37C

Question 24

optimal pH for enzymes in the human body is

Answer 24

7.4

Question 25

Enzymes that are _ have multiple binding sites

Answer 25

allosteric

Question 26

allosteric sites are?

Answer 26

regulate the availability of the active site

Question 27

molecules binding to the allosteric site are called

Answer 27

allosteric activators or allosteric inhibitors

Question 28

describe what is the binding site, impact on Km, and impact on Vmax for competitive, noncompetitive, mixed, and uncompetitive inhibitors

Answer 28

competitive = active site; Km increases; Vmax unchanged
non-competitive = allosteric site; Km unchanged; Vmax decreases
Mixed= allosteric site; Km increases or decreases; Vmax decreases
Uncompetitive= allosteric site; Km decreases; Vmax decreases