Allosteric Enzymes

Question 1

Allosteric enzymes usually display ___ cooperatively with their substrate

Answer 1

positive

Question 2

In regards to allosteric enzymes, the binding of one substrate molecule facilitates….

Answer 2

the binding of subsequent molecules to the enzyme

Question 3

Allosteric enzyme has more than one ___ ___ site

Answer 3

substrate binding

Question 4

v = Vm[S]^n / K0.5 + [S]^n

What is this equation’s name?

Answer 4

the hill equation

Question 5

The Hill number (n) is a measure of the degree of ___

Answer 5

cooperativity

Question 6

The larger the value of n, the greater the cooperativity, and the greater the ____ of the curve

Answer 6

sigmoidocity

Question 7

If n = 1, describe the cooperativity

Answer 7

there is none

Question 8

Explain the difference between K0.5 and Km since both represent [S] at 1/2 Vmax

Answer 8

since the rate constants for an allosteric enzyme are different than those for a michaelis-menten enzyme, the two constants are not equal

Question 9

Enzymes with positive cooperative kinetics have a more ___ range of activity response to [S] and act more like a “___”

Answer 9

narrow; switch

Question 10

Allosteric enzymes may be in a “tense” or “relaxed” conformation. At low [S], the enzyme is in the ____ conformation. Binding of [S} promotes a conformation change to the ____ conformation

Answer 10

tense; relaxed

note: tense is inactive, relaxed is active

Question 11

The binding of S to an allosteric enzyme, which increases the affinity of the other catalytic sites for S is an example of ____ regulation

Answer 11

Homotropic

Question 12

True or false? Homotropic regulation is almost always negative

Answer 12

false; postive

Question 13

Hetertropic regulation - describe

Answer 13

a regulatory molecule distinct from the substrate which binds to a site other than the catalytic site and modulates the activity of the enzyme

Question 14

Heterotropic effectors interact with a site other than the active site. They can have a ___ or a ___ effect.

Answer 14

postive or negative

Question 15

In regards to heterotropic effectors, what do V-system effectors do?

Answer 15

the effectors may affect the catalytic rate, and thus influence the Vmax - can be positive or negative

Question 16

In regards to heterotropic effectors, what do K-system effectors do?

Answer 16

effectors affect the binding of substrate and thus influence the K0.5 - can be positive or negative

Question 17

Describe what V-system effectors look like on a plot

Answer 17

Positive or negative lines star off with uninhibited line and then as the slope increases, the V-system effectors go higher or lower but maintain the same sigmoidal curve

Question 18

Describe what K-system effectors look like on a plot

Answer 18

Positive or negative lines start at 0 with uninhibited line but then immediately go vertical (positive) or more horizontal (negative) and do not retain sigmoidal shape