3- enzymes

Question 1

Which statement is true of a competitive enzyme inhibitor?

Answer 1

effects can be overcome by adding more substrate

Question 2

Which statements about enzyme inhibitors are correct?

1 - competitive inhibitors may be similar shapes to the substrate

2 - competitive inhibitors bind to the active site

3 - non-competitive inhibitors alter the shape of the enzyme

4 - non-competitive inhibitors bind to the substrate

Answer 2

1, 2, 3

Question 3

Why do large increases in the temperature or pH alter enzyme activity?

1 - they change the three-dimensional shape of the enzyme

2 - they disrupt hydrogen and ionic bonds in the enzyme

3 - they increase hydrophobic interactions in the enzyme

Answer 3

1, 2

Question 4

What is the effect of an enzyme in an enzyme-catalysed reaction?
effect on activation energy+energy yield

Answer 4

decreases the activation energy and has no effect on the energy yield

Question 5

Strength of bonds in enzyme

Answer 5

weak H bonds- stabilise secondary structure of alpha-helix/beta-pleated sheets

ionic bonds(electrostatic interactions) contribute to overall tertiary structure between side chains

Van der Waals interactions stabilise protein’s tertiary strcuture by allowing hydrophobic side chains to interact with each other

disulfide bonds(covalent) strong- between sulfure atoms of 2 cysteine amino acids in tertiary structure

peptide bonds strongest

Question 6

what happens when enzyme denatured

Answer 6

bonds are broken between the R groups of the amino acids in the polypeptide chains of the enzyme

tertiary structure of the enzyme is altered

shapes of the active site and the substrate are no longer complementary

Question 7

What is the definition of the Michaelis-Menten constant, Km, for an enzyme

Answer 7

substrate concentration that gives half Vmax

Question 8

What determines the specificity of an enzyme

Answer 8

covalent and other bonding between R groups of the polypeptide

Question 9

By which method can immobilised enzymes be produced?

Answer 9

enclosing enzymes within a partially permeable membrane
by: attach insoluble, inert material (calcium alginate). forms gel capsule

Question 10

+: immobilising enzymes

Answer 10

• easily separated from products and reused
• more stable enzyme- can withstand changes to pH+temp in solution
• allows more product formed

Question 11

what makes an enzyme globular

Answer 11

• spehrical shaped
• water soluble - AMINO ACIDS WITH hydrophilic R groups on outside, phobic on inside