Enzymes

Question 1

Name the four types of specificity and what they are.

Answer 1

absolute - catalyzes only one reaction

group - acts on one type of molecule

linkage - acts on particular type of bond

stereochemical - acts on particular steric or optical isomer

Question 2

Describe the energy diagram and how it changes with the presence of an enzyme.

Answer 2

Question 3

coenzyme

Answer 3

a non-protein organic substance which is dialyzable, thermostable and loosely attached to the apoenzyme

organic molecules that provide functional groups; participate in activation transfer and redox reactions

Question 4

prosthetic group

Answer 4

an organic substance which is firmyl attached to the apoenzyme (heme)

Question 5

apoenzyme

Answer 5

the inactive form of an enzyme lacking its cofactors

Question 6

holoenzyme

Answer 6

the active form of enzymes that includes the cofactors

Question 7

What is the Michaelis-Menten equation and what does it mean?

Answer 7

Vmax is the velocity that can be achieved at infinites bustrate concentration

Km is the concentration of substrate required to achieve 1/2 Vmax

Question 8

Describe ther Linkeweaver-Burk transformation.

Answer 8

Question 9

turnover number

Answer 9

the number of substrate molecules converted into product by an enzyme molecule in a unit time when the enzyme is fully saturated

Question 10

Describe competitive inhibition and its effects on Km and Vmax

Answer 10

bind at the substrate recognition site and prevent substrate from binding, increase Km but has no effect on Vmax

Question 11

Describe non-competitive inhibition and how it affects Km and Vmax.

Answer 11

do not compete with substrate for binding, but may compete with a second substrate or otherwise interfere with the active site, lowers Vmax and no effect on Km

Question 12

Describe uncompetitive inhibition and its effect on Km and Vmax.

Answer 12

bind only to enzymes already containing substrate, decrease vmax and the Km

Question 13

reactive inhibitors

Answer 13

substrate analogs that form covalent bonds with amino acid side chains in the active site, contain highly reactive functional groups

Question 14

transition state analogs

Answer 14

structure resembles the transition state of the natural substrate, cannot be converted to product and not covalently bound

Question 15

Describe cooperativity in ligand binding.

Answer 15

Question 16

allosteric or second “second site” control

Answer 16

activators stabilize the active conformation of the enzyme and inhibitors stabilize the inactive state, cahnge the Km but not the Vmax

usually does not bind the active site

Question 17

regulation by compartmentation

Answer 17

compartmentation into organelles or multi-enzyme complexes increases efficiency

Question 18

isozymes

Answer 18

members of a protein family that have very similar sequences and are either products of different genes or produced from the same gene by alternative splicing

Question 19

glucokinase vs. hexokinase

Answer 19

glucokinase is specific to liver, much higher Km, only maximally active at high glucose concentrations

hexokinase has a lower Km so at low concentrations is th eprimary enzyme in action

Question 20

feedback inhibition vs. feedback regulation vs. product inhibition

Answer 20

feedback inhibition - a downstream product directly inhibits an enzyme, fast

feedback regulation - a product inhibits enzyme production through transcription, slow

product inhibition - product of a reaction inhibits the enzyme, immediate

Question 21

feedforward activation

Answer 21

products of a reaction activate enzymes of a downstream pathway