Enzymes

Question 1

enzyme general properties

Answer 1

catalysts that direct the pathways of cellular metabolism, remains unchanged themselves

Question 2

components of an enzyme

Answer 2

apoenzyme: protein component of an enzyme
cofactor: required by some enzymes, could be a metal ion, co-enzyme, or prosthetic group
holoenzyme: comple enzyme

Question 3

enzyme classifications

Answer 3

1. oxidoreductases: transfer of e-
2. transferases: group transfer rxns
3. hydrolases: hydrolysis rxns
4. lyases: formation of double bond
5. isomerases: transfer of groups w/in molecules
6. ligases: formation of bonds through condensation rxns

Question 4

rate or velocity definition

Answer 4

the speed of a chemical rxn, whether catalyzed or uncatalyzed

Question 5

catalyst

Answer 5

increases the rate of a chemical rxn but is not itself changed in the process

Question 6

substrate

Answer 6

reactants involved in enzymatic rxns

Question 7

important enzyme characteristics

Answer 7

1. enzyme is not changed
2. enzyme does not change the equilibrium constant of the rxn, just increases the rate it reaches it
3. decrease the free energy of activation

Question 8

enzyme specificity

Answer 8

highly specific, either for one type or rxn or one substrate (broad and narrow specificity)

Question 9

factors that effect enzymes

Answer 9

optimal temp: increase in temp before too hot
optimal pH: for proper ionization
conc. of enzyme and substrate

Question 10

michaelis-menten equation

Answer 10

Vo= Vmax[S]/Km+[S]

Question 11

michaelis constant

Answer 11

Km (michaelis constant)= [S] at 1/2 Vmax
lower Km means high affinity

Question 12

lineweaver-burk plot/equation

Answer 12

1/Vo= (Km/Vmax[S]) + (1/Vmax)
plot: y-axis (1/Vo) x-axis (1/[S])
- slope= Km/Vmax
- x-intercept= -1/Km
- y-intercept= 1/Vmax

Question 13

enzyme inhibition

Answer 13

reversible enzyme inhibitors: bind noncovalently
irreversible enzyme inhibitors: bond covalently and chemically change them

Question 14

competitive inhibition

Answer 14

a substance that directly competes with enzyme
- Vmax remains the same
- Km increase (lower affinity)

Question 15

noncompetitive inhibition

Answer 15

inhibitor binds to a different site on the enzyme, leading to no rxn
- Vmax decreases
- Km is unchanged

Question 16

regulatory enzyme

Answer 16

catalyze the first/early rxn in a metabolic sequence

Question 17

rate-limiting (rate-determining) step

Answer 17

regulatory enzymes catalyze this step, to control overall pathway

Question 18

committed step

Answer 18

a chemical rxn that is unique to a specific pathway

Question 19

feedback inhibition

Answer 19

occurs by end products

Question 20

allosteric enzyme

Answer 20

activity is regulated by noncovalent interactions at sites other than the catalytic sites

Question 21

allosteric site

Answer 21

unique region of an enzyme that affects catalysis

Question 22

allosteric enzyme regulation

Answer 22

positive and negative allosteric effectors can affect affinity of enzyme for its substrate, maximal catalytic activity, or both