Enzymology

Question 1

enzymology

Answer 1

the study of enzymes

Question 2

enzymes’ purpose

Answer 2

to make rxns occur faster than they would on their own (but cannot alter the equilibrium for a rxn)

Question 3

active site

Answer 3

where substrates bind to enzymes; determined by the three-dimensional structure of the enzyme

Question 4

cofactor

Answer 4

a non-protein component of an enzyme (e.g. a mineral)

Question 5

reaction specificity

Answer 5

the specific reaction that the enzyme catalyzes

determined by the physicochemical properties of the enzyme’s active site

Question 6

generally, what is an active site composed of

Answer 6

a substrate binding site

a catalytic site

Question 7

what determines substrate specificity

Answer 7

size
structure
charges
polarity
hydrophobicity 

(of the active site)

Question 8

coenzyme

Answer 8

an organic cofactor. ex. most vitamins

Question 9

prosthetic group

Answer 9

used to describe a covalently bound cofactor

Question 10

cofactor/coenzyme purposes

Answer 10

provide functional groups in the active site of an enzyme that are required for substrate binding or the enzymatic process

provide charge stabilization in the transition state (e.g., metal ions)

Question 11

oxidoreductases

Answer 11

oxidation/reduction; transfer of reducing equivalents (i.e. electrons) from one compound to another

Question 12

transferases

Answer 12

move functional groups from one substrate to another

Question 13

hydrolases

Answer 13

break larger molecules into smaller molecules by the addition of water; also catalyze group transfer (with the acceptor molecule being water)

Question 14

lyases

Answer 14

enzymes that cleave covalent bonds without using water; remove groups (e.g. NH3 or CO2) from a substrate

Question 15

isomerases

Answer 15

rearrange atoms within a molecule without affecting the molecule’s overall atomic composition

Question 16

ligases

Answer 16

use ATP to catalyze energy-dependent synthetic rxns (i.e. formation of covalent bonds)

Question 17

dehydrogenases enzyme type

Answer 17

oxidoreductase

Question 18

kinase enzyme type

Answer 18

transferases

Question 19

hydrolase examples

Answer 19

proteases

lipases

amylases

Question 20

proteases

Answer 20

catalyze hydrolytic cleavage of proteins

Question 21

lipases

Answer 21

catalyze hydrolytic cleavage of lipids

Question 22

amylases

Answer 22

catalyze hydrolytic cleavage of carbohydrates

Question 23

glutamate decarboxylase enzyme type and role

Answer 23

lyase

removes CO2 from glutamate, producing GABA

Question 24

histidine decarboxylase enzyme type and role

Answer 24

lyase removes CO2 from histidine, producing histamine

Question 25

peroxidases and oxidases enzyme type

Answer 25

oxidoreductase

Question 26

cytochrome P450 enzyme type

Answer 26

oxidoreductase for liver detoxification

Question 27

glucokinase enzyme type and role

Answer 27

transferases

moves a phosphate group from ATP to glucose

Question 28

transaminases enzyme type

Answer 28

transferase

Question 29

alanine transaminase (ALT) enzyme type and role

Answer 29

transferase

reversibly move an amino group from an amino acid donor to pyruvate or oxaloacetate, generating alanine

Question 30

aspartate transaminase (AST) enzyme type and role

Answer 30

transferase

reversibly move an amino group from an amino acid donor to pyruvate or oxaloacetate, generating aspartate

Question 31

triose phosphate enzyme type

Answer 31

isomerase in the glycolytic pathway

Question 32

phosphoglucomutase enzyme type

Answer 32

isomerase in the glycogenolysis/glycogenesis pathway

Question 33

aminoacyl-tRNA synthetase enzyme type

Answer 33

ligase

Question 34

oxidoreductase cofactors

Answer 34

often use the reducing equivalents NAD+/NADH or NADP+/NADPH (both derived from niacin aka vitamin B3)

also use as iron-sulfur clusters, heme, and vitamin C

Question 35

two main factors affecting ligand binding

Answer 35

enthalpy (ligand/protein interactions with water, i.e. overcoming dehydration effect)

entropy (ligand or receptor polarization, conformation, or flexibility)

Question 36

lock-and-key model

Answer 36

the active site is complementary and specific for a given substrate(s)

(outdated theory)

Question 37

induced fit model

Answer 37

the binding of a substrate within the active site causes conformational changes within the enzyme such that the number of interactions is increased

Question 38

two important environmental variables influencing enzyme activity

Answer 38

temperature

pH

Question 39

Michaelis-Menten equation

Answer 39

Vmax * [S]
vo = ————–
Km + [S]

Question 40

Michaelis constant

Answer 40

Km

the substrate concentration in which the rate of the reaction (velocity) is ½ of Vmax

inverse relationship with affinity of enzyme for substrate

Question 41

Vmax (enzyme kinetics)

Answer 41

the maximum velocity of the reaction that can occur in the presence of an infinite substrate concentration

Question 42

Michaelis-Menten equation assumtions

Answer 42

1) the substrate (S) binds to the enzyme (E) forming an intermediate called the enzyme-substrate complex (ES)
2) ES breaks down to the enzyme plus product (P)
3) (E), (S), and (ES) are all in rapid equilibrium with one another, so that a steady-state concentration of (ES) is rapidly achieved
4) decomposition of (ES) to (E) + (P) is the rate-limiting step in catalysis

Question 43

isoteric enzyme

Answer 43

single-shaped enzyme

Question 44

allosteric enzymes

Answer 44

multimeric and the activity of allosteric enzymes is regulated by ‘effector molecules’ (allosteric effectors), which bind to the enzyme at a site that is distinct and physically separate from the active site

don’t exhibit Michaelis-Menten kinetics