Enzymes and Enzymes Kinetics

Question 1

Enzyme Classification

Answer 1

Oxidoreductases: Oxidation-reductions

Transferases: Functional group transfer reactions

Hydrolases: Hydrolysis reactions

Lyases: Reactions involving group elimination to form double bonds

Isomerase: Isomerisation reactions

Ligases: Reactions involving bond formation coupled with ATP hydrolysis

Question 2

Forces that determine substrate specificity

Answer 2

Van der Walls forces such as:
hydrogen bonding
charge-charge (electronic) interactions
hydrophobic interactions

Question 3

Binding of substrate is due to —————————————————

Answer 3

van der Walls, electrostatic, hydrophobic interactions

Question 4

Cu2+, Fe2+, Zn2+
are…..

Answer 4

Cofactors

Question 5

(organic molecules) NAD, FAD, Co-Enzyme A are:

Answer 5

Coenzymes or Co-Substrates

Question 6

Heme group in cytochrome c

Answer 6

Prosthetic groups

Question 7

———— the rate of a reaction (varies with reactant concentration)

Answer 7

Velocity (v)

Question 8

———— indicates the speed or efficiency of a reaction

Answer 8

Rate constant (k)

Question 9

Rate equation: v = k[S1]1[S2]1
For reactions: S1 + S2 P1 + P2

Answer 9

Second order reaction
Rate is determined by the concentration of both substrates

Question 10

D[P] / Dt = v = k[S]

Answer 10

First Order Rate Equation

Question 11

S1 + S2=P1 + P2
v = k[S1]1[S2]0 = k’[S1]1

If the concentration of one reactant is so high that it remains essentially constant, reaction becomes zero order with respect to that reactant

Overall reaction is ————————–

Answer 11

pseudo first-order

Question 12

complex formed when specific substrates fit into the enzyme active site

Answer 12

Enzyme-substrate complex (ES)

Question 13

When [S]&raquo_space; [E], every enzyme binds a molecule of substrate (enzyme is saturated with substrate)
Under these conditions the rate depends only upon [?], and the reaction is ————–

Answer 13

Enzyme
pseudo-first order

Question 14

Enzyme-catalyzed Reaction can be monitored by:

Answer 14

Formation of a product or disappearance of substrate.

Question 15

Velocity at the beginning of an enzyme-catalyzed reaction is

Answer 15

Initial velocity (vo)

Question 16

Michaelis Menten Equation

Answer 16

Vmax[S]
v =
Km + [S]

Equation describes v versus [S] plots
Km is the Michaelis constant

Question 17

————–: expressed µmoles of product formed per minute per milligram protein and is designated as IU (International Units)

Answer 17

Enzyme activity

Question 18

————- is reached when an enzyme is saturated with substrate (high [S])

Answer 18

Maximum velocity (Vmax)

Question 19

At high [?] the reaction rate is independent of [s] (zero order with respect to s)

Answer 19

Substrate

Question 20

At low [?] reaction is first order with respect to S

Answer 20

Substrate

Question 21

The shape of a v versus [S] curve is a rectangular hyperbola, indicating:

Answer 21

saturation of the enzyme active site as [S] increases

Question 22

Substrate concentration at which reaction velocity is half-maximal

Answer 22

Michaelis constant (Km)

Question 23

Smaller the Km, an enzyme achieves Vmax at ——-substrate concentration

Answer 23

lower
hence the enzyme is more efficient

Question 24

T or F
Km is dependent on temperature and pH

Answer 24

T

Question 25

Substrates (substances) that reduce an enzyme’s activity are know as

Answer 25

inhibitors
- Reversible inhibition
- Irreversible inhibition - inactivates the enzyme

Question 26

Types of enzyme inhibitors

Answer 26

Competitive inhibitors
Un-competitive inhibitors
Non-competitive inhibitors

Question 27

Inhibitor binds only to free enzyme (E) not (ES)

Answer 27

Competitive Inhibition

Question 28

T or F
Vmax is the same with or without I (high S can still saturate the enzyme even in the presence of I)

Answer 28

T

Question 29

T or F
Apparent Km measured in the presence of I is larger than Km (in absence of I)

Answer 29

T

Question 30

T or F
Competitive inhibitors does not resemble the substrate

Answer 30

F