ENZYMES: structure

Question 1

what is the general shape/material of enzymes?

Answer 1

• Almost always soluble, globular proteins (although there are a small number of RNA enzymes)

Question 2

can enzymes have one or more pp chains?

Answer 2

yes - most are oligomers, some are monomeric

Question 3

deifne: monomeric enzyme

Answer 3

single pp chain with one binding site, eg. ribonuclease

Question 4

define: oligomers

Answer 4

atleast two pp chains (same or different), with multiple binding sites

Question 5

All enzymes have an__

Answer 5

active site?

Question 6

how is the active site formed?

Answer 6

by the folding of pp chains to form a small region with a unique specific 3D shape. This region is small, made of about 3-12 amino acids

Question 7

what happens when the active site is altered?

Answer 7

it may not be complementary to the substrate and its functionality will be permanently/temporarily lost/reduced.

Question 8

describe the bonds between the enzyme and substrate.

Answer 8

stabilise the enzyme-substrate complex. can be hydrogen/ionic, or covalent

Question 9

3 types of specifity?

Answer 9

absolute/substrate, bond, group specifitty

Question 10

define: absolute/substrate specificity

Answer 10

an enzyme can act on one substrate only (lactase can only hydrolyse lactose to form galactose and glucose)

Question 11

define: bond specificity

Answer 11

enzyme can act on only one kind of bond (peptidase can only act on peptide bonds between 2 amino acids)

Question 12

define: group specificity

Answer 12

enzyme can only act on molecules with particular functional group(s) surrounding a bond (trypsin can only act on bonds adjacent to amino acids with basic side chains – lysine and arginine)