Module 6 - Enzymes

Question 1

Explain how to experimentally determine Km and Vmax.

Answer 1

Question 2

For a uncompetitive inhibition, what’s the apparent V_max and K_m?

Answer 2

V_max=V_max/α’ and K_m= K_m/α’

Question 3

Explain how enzymes speed up chemical reactions.

Answer 3

Enzymes increases reaction rates by lowering the activation energy required to convert a substrate to a product, performing this function with a high degree of specificity. Enzyme catalysed reactions are characterized by the formation of a complex between enzyme and substrate.

Question 4

List with examples the common types of enzymes.

Answer 4

1. Kinase: transfer of phosphoryl from one molecule (ATP) to another
2. Phosphorylase: catalyses the covalent addition of Pi to a molecule
3. Phosphatase: dephosphorylation of substrate
4. Dehydrogenase: catalyses an oxidation/reduction reaction
5. Mutase: shift phosphoryl group between atoms of the same molecule
6. Isomerase: conversion between isomers
7. Synthase: synthesize a product
8. Hydratase: addition/removal of water

Question 5

List three ways enzymes catalyse reactions.

Answer 5

• acid-base catalysis: gives and takes protons
• covalent catalysis: change reaction paths
• metal ion catalysis: use redox cofactors

Question 6

For a competitive inhibition, what’s the apparent V_max and K_m?

Answer 6

V_max=V_max and K_m= αK_m

Question 7

Discuss why enzymes are important in biology, medicine, and industry.

Answer 7

Some diseases are caused by either excessive or a deficiency in enzymatic activity. For example, PKU is a disease caused by a deficiency in ethe enzyme phenylalanine hydroxylase. Other than that, many drugs can target enzymes by inhibiting or activating enzyme target; RELENZA inhibits the enzyme Neuraminidase form flu virus. Knowing the mechanisms of these enzymes would assist in the treatment of these diseases/disorder.

Question 8

For a mixed inhibition, what’s the apparent V_max and K_m?

Answer 8

V_max=V_max/α’ and K_m= αK_m/α’

Question 9

Differentiate between irreversible and reversible inhibitors.

Answer 9

Irreversible inhibitors bind covalently to the active site, destroy a functional group essential for enzyme activity, ot form a stable noncovalent complex with the enzyme.

Reversible inhibitors bind reversibly to enzymes and inhibit the enzyme either by competitive, uncompetitive, or mixed modes of inhibition.