Enzymes

Question 1

Amount of product formed per unit time

Answer 1

Velocity

Question 2

The ______is in the linear part of the M-M curve

Answer 2

initial velocity

Question 3

At high concentration of substrate ({S}»Km) the velocity of the reaction is ______–that is constant and independent of ______

Answer 3

At high concentration of substrate ({S}»Km) the velocity of the reaction is zero order–that is constant and independent of substrate concentration

Question 4

At low concentration of substrate ({S}<

Answer 4

proportional

Question 5

When [S] = 0, v=

Answer 5

0

Question 6

When [S] less than Km

Answer 6

v=(Vmax / (Km ) * [S]

Question 7

When [S] is infinite, v=

Answer 7

Vmax

Question 8

When [S] is equal to Km, v=

Answer 8

v=1/2(Vmax)

Question 9

Small Km reflects a _____ affinity of enzyme for the substrate

Answer 9

high

Question 10

Large Km reflects a _____ affinity of enzyme for the substrate

Answer 10

low

Question 11

Michaelis-Menten kinetic analysis:

Does not require ____

Answer 11

pure enzyme

Question 12

TO MEASURE ENZYME use

Answer 12

saturating amounts of

substrate (»Km)

Question 13

TO MEASURE SUBSTRATE

Answer 13

use low substrate levels (lower or at the Km)

Question 14

If there’s more enzyme (Vmax) Km (does/does not) change

Answer 14

does not

Question 15

Also called the “turn-over” number = how many substrate molecules can be used per second

Answer 15

Kcat

Question 16

The Kcat =

Answer 16

The Kcat = Vmax/the enzyme concentration

Question 17

LB plot:

X intercept=

Answer 17

intercept=-1/Km

Question 18

LB plot:

Y-intercept

Answer 18

1/Vmax

Question 19

LB plot:

Slope

Answer 19

Km/Vmax

Question 20

Competitive inhibitors bind to

Answer 20

binding site only

Question 21

Noncompetitive inhibitors bind to

Answer 21

catalytic machinery only

Question 22

Irreversible inhibitors

Answer 22

Kill the enzyme

Question 23

Ki

Answer 23

inhibitor constant. Inversely related to affinity constant of the inhibitor for the enzyme.

Question 24

The lower the Ki, the ____ it binds

Answer 24

The lower the Ki, the tighter it binds

Question 25

Irreversible inhibitors

Example

Answer 25

Compound DIFP inhibits serine protease

Question 26

Competitive inhibitors change _____, but not _____

Answer 26

change Km, but not Vmax

Question 27

Noncompetitive inhibitors change ____, but not ____

Answer 27

change Vmax, but not Km

Question 28

Irreversible inhibitors change ______, but not _____

Answer 28

Irreversible inhibitors change Vmax, but not Km

Question 29

5 ways to regulate enzymes

Answer 29

1. Regulation by Location
2, Enzyme Zymogens
3. Protein inhibitors
4. Protein phosphorilation
5.Regulation by Substrate Levels

Question 30

Example of: Regulation by Location

Answer 30

Enzymes in Blood Plasma: common indicator of liver damage is alanine transaminase (ALT). (A liver enzyme that balances amino acid levels). A high level is indicative of cell damage.

Question 31

Example of: Protein Inhibitors

Answer 31

“anti-elastase” in lung tissue.

Oxidized a1-antitrypsin does not effectively inhibit elastase–>Elastase cleaves elastin–>Lung scarring & emphysema

Question 32

The basic concept is that phosphorylation or dephosphorylation modifies the charge of an amino acid residue. If the serine, threonine, or tyrosine is in or near the active site of an enzyme, the enzyme activity may be changed.

Answer 32

Protein Phosphorylation

Question 33

Changes in the substrate concentration changes enzyme activity

Answer 33

Regulation by Substrate Levels

Question 34

Allosteric enzymes are more sensitive to substrate and (4)

Answer 34

• Usually contain multiple subunits
• Does not usually follow Michaelis -Menten kinetics; can define an ‘apparent’ Km
• Usually have binding sites for affector molecules
• Often regulate a reaction pathway

Question 35

An allosteric enzyme is often at ______

Answer 35

at the beginning of a dedicated reaction pathway

Question 36

Allosteric enzymes exist in ___ and ____ forms and

have binding sites for effectors

Answer 36

R and T forms

Question 37

_____ is the inhibition of the

product of the reaction

Answer 37

Direct product inhibition

Question 38

_______ is

typically the product inhibiting an earlier reaction

Answer 38

Feedback inhibition