Lecture 6 & 7

Question 1

What are four properties of enzymes?

Answer 1

Specific
Catalytic power (fast)
Efficient
Regulated

Question 2

What is specificity?

Answer 2

Ability of the enzyme to specifically recognise the proper substrate (reactant)
* Enzyme-substrate recognition and specificity is based on structural complementarity
▪ 3-D fit

Question 3

What is the active site?

Answer 3

The active site, is a three-dimensional pocket, located in
a small enzyme region (~10–20%), which is composed of:
- substrate binding site
- catalytic site

Question 4

What happens in the substrate binding site?

Answer 4

• amino acid side chains interact with the the substrate
• through H-bonds and other electrostatic interactions
• to Orientate the substrate within the active site

Question 5

What happens in the catalytic site?

Answer 5

Amino acids that catalyse the reaction

Question 6

What is catalytic power?

Answer 6

An enzyme’s ability to speed up the rate of reaction between 10 to the 6 or 10 to the 7x faster

Question 7

What are the three reasons enzymes are efficient?

Answer 7

• Not altered or
  consumed during
  or after the reaction

*They are reusable

• They are active at very low concentrations

Question 8

What factors affect enzyme function?

Answer 8

-Temperature
-ionic conditions
-pH
-Substrate concentration
- Presence of inhibitors

Question 8

Break down enzyme activity due to temperature

Answer 8

• enzymes have a high optimum temperature (37 in humans)
• lower activity at lower temperature
• will begin to lose activity at high temperatures past optimum = denaturation

Question 9

What happens during denaturation?

Answer 9

• loss of natural folding of enzyme
• active site and substrate no longer match
  -loss of catalytic activity

Question 10

How does substrate conc affect enzyme activity?

Answer 10

At a constant conc of enzyme, an increase in substrate conc will increase the reaction rate until enzyme becomes saturated
=VMAX

Question 10

What is Km?

Answer 10

the concentration of substrate at
which the reaction rate is half-maximal

Question 11

What is the relationship between Km and enzyme binding?

Answer 11

• the higher the Km = the weaker the bonding
• the lower the Km = the stronger the bonding

Question 12

What is a co-factor?

Answer 12

An additional non-protein reactive group that are essential for activity

Question 13

What are the two types of co-factors?

Answer 13

essential ions and co-enzymes
(Cosubstrates & prosthetics)

Question 14

What does a co-substrate entail?

Answer 14

Weakly/temporarily bound to an
enzyme
* Consumed and transformed during
the reaction and dissociate from the
active site (regenerated in another enzymic
reaction and recycled)

Question 15

What do prosthetic groups entail?

Answer 15

• Tightly or permanently bound to the enzyme
• Are not consumed or altered during reaction

Question 16

What is a holoenzyme?

Answer 16

A complete catalytically active enzyme together with its co-factor

Question 17

What is an apoenzyme?

Answer 17

the protein part of the enzyme without its co-factor (not active)

Question 18

What type of reactions are Oxidoreductases involved in?

Answer 18

Oxidation & Reduction (REDOX) reactions

Question 19

What are transferases involved in?

Answer 19

• Functional group transfer reactions
• Includes kinases

Question 20

What are hydrolyses involved in?

Answer 20

• Cleavage of chemical bonds through the addition of
  water molecules (proteases, phosphatases, etc)

Question 21

What are lysases involved in?

Answer 21

• Breaking of chemical bonds within a molecule,
  without the involvement of water

Question 22

What are isomerases involved in?

Answer 22

• Conversion of one isomer into another one

Question 23

What are ligases involved in?

Answer 23

• Joining of two molecules

Question 24

What are translocases involved in?

Answer 24

• Movement of molecules or ions across membranes

Question 25

How much ATP does the oxidation of NADH yield?

Answer 25

2.5 ATP

Question 26

How much ATP does the oxidation of FADH2 yield?

Answer 26

1.5 ATP