6. Enzymes

Question 1

thermodynamics is ___ kinetics

Answer 1

IS NOT

Question 2

what is the transition state

Answer 2

the highest energy state / top of energy hill

• molecules must pass for a reaction to take place
• NOT an intermediate

Question 3

what is activation energy

Answer 3

Ea = the difference between energy levels @ ground state and transition state

Question 4

what is the rate-limiting step

Answer 4

the step with the highest activation energy

Question 5

what is the activation energy linked to?

Answer 5

linked to rate of reaction (kinetics)

Question 6

what do enzymes do

Answer 6

• increase reaction rates by lowering activation energy

Question 7

what is the induced fit hypothesis

Answer 7

-binding of substrate to active site requires substrate to take on conformation similar to transition state
-upon binding of substrate, the enzyme also changes its conformation (induced fit)

• energetically favourable

Question 8

4 properties of enzymes

Answer 8

1. do NOT affect equilibrium
2. highly specific
3. highly regulated
4. are NOT changed by the reaction

Question 9

can enzymes affect free energy of a reaction? delta G

Answer 9

NO

Question 10

enzyme structure

Answer 10

apoenzyme + cofactor -> holoenzyme

the cofactor may be:
- inorganic ion (metal ion)
- coenzyme (NAD/FAD)

Question 11

what is the ES vs EP complex

Answer 11

ES complex - substrates bound to enzyme

EP complex - products bound to enzyme

Question 12

describe the active site

Answer 12

• site of catalysis!
• small region of enzyme where substrate molecules bind
• usually 3/4 AA residues

Question 13

what are substrates

Answer 13

reactants that the enzyme acts on

Question 14

enzyme activity can be measured by (2)

Answer 14

• amount of product formed per unit time
• amount of substrate consumed per unit time

micromol / minutes = U

Question 15

velocity refers to …..

Answer 15

initial rate of reaction / slope = initial rate