Term 1- Lec 11- Enzyme Kinetics

Question 1

Initial rxn rate (Vo or Vi)

Answer 1

Rate of reaction measured over a brief initial period while [S] is till high and [P] is still low

Question 2

Statin drugs

Answer 2

Are competitive inhibitors of cholesterol synthesis, thus they reduce the amount of cholesterol synthesized and lower plasma cholesterol concentration

Question 3

Equation for Km

Answer 3

Km is equal to the amount of substrate (y-axis) at (Vmax/2)

Question 4

The rate of the reaction is:

Answer 4

The value for Vo

Question 5

Rxn is said to be what order when [S]«<Km

Answer 5

First order. Vo and [S] are proportional, if you double [S] you get double Vo

Question 6

Rxn is said to be what order when [S]»>Km

Answer 6

Zero order. Enzyme is saturated, all enzyme active sites are filled

Question 7

Vmax

Answer 7

Vmax is NOT a constant, is dependent on [E]

Question 8

Kcat

Answer 8

Represents the efficiency of an enzyme. Measures the formation of product per second and per molecule.

Question 9

Competitive inhibitors

Answer 9

• Have similar structure to the substrate

* Compete with the substrate for the active site

Question 10

Km

Answer 10

Km IS a constant, thus an intrinsic property of an enzyme. Inversely related to the binding affinity of an enzyme

Question 11

High Km

Answer 11

Low affinity for the substrate

Question 12

Low Km

Answer 12

High affinity for the substrate

Question 13

Isoenzymes

Answer 13

Isoenzymes are different enzymes that catalyze the same reaction, but differ in everything else (gene, 1º sequence, rxn rates)

Question 14

An example of isoenzymes and what the produce

Answer 14

Glucokinase and hexokinase. They both produce glucose-6-phosphate

Question 15

Non-competitive inhibitors

Answer 15

bear little resemblance, if any, to the enzyme’s substrate. Bind at a site other than the active site and cause conformational change that still allows the enzyme to bind substrate, but is less eficient.

Question 16

Is competitive inhibition reversible

Answer 16

Yes

Question 17

Is non-competitive inhibition reversible

Answer 17

Yes

Question 18

Example of a competitive inhibitor

Answer 18

Statins—cholesterol, methanol—anti-freeze

Question 19

Example of a non-competitive inhibitor

Answer 19

Plavix

Question 20

Example of a suicide substrate

Answer 20

Disulfiram for aldehyde dehydrogenase

Question 21

What are suicide substrates

Answer 21

Cannot bind the active site of the target enzyme in the form it is digested. Must be modified through several steps before taking the form that irreversibly binds the target enzyme’s active site