Enzymes And Catalysis (w3)

Question 1

What are enzymes ?

Answer 1

Biological catalysts which speed up specific enzymatic reactions and are present in all organisms.

Question 2

What enzyme isn’t a protein ?

Answer 2

Catalytic RNAs (Ribozymes)

Question 3

What are the 4 enzyme properties ?

Answer 3

1. Substrate specificity (reactants)
2. Catalytic power (fast)
3. Efficient (not altered after the reaction)
4. Cab be regulated

Question 4

What is enzyme specificity ?

Answer 4

The ability to specifically recognize a proper substrate (reactant) - it uses the molecular recognition mechanism to form enzyme-substrate complexes.

Question 5

What is an active site ?

Answer 5

A three dimensional pocket or groove found in a small region of the enzyme composed of both a substrate binding site and a catalytic site.

Question 6

What does catalytic power do ?

Answer 6

Increases the rate of a chemical reaction.

Question 7

Define activation energy …

Answer 7

The minimum amount of energy required to start any reaction.

Question 8

What happens to enzymes after reactions ?

Answer 8

They remain unaffected by the reaction which they catalyst so can be reused.

Question 9

Are enzymes more efficient at low or high concentrations ?

Answer 9

More efficient at low concentrations.

Question 10

What conditions affect enzyme function ?

Answer 10

• Temperature
• Ionic conditions
• pH
• Substrate concentration
• Presence of inhibitors

Question 11

What is the optimum temperature for enzymes to provide high rate reactions in humans ?

Answer 11

37 degrees

Question 12

What is the optimum pH for enzymes in the small intestine and stomach. And how does pH affect enzymes ?

Answer 12

• small intestine = 7.5
• stomach = 1.5

They lose activity in low or high pH as the tertiary structure is disrupted.

Question 13

How does substrate conc affect enzyme activity ?

Answer 13

Increasing substrate concentration will increase enzyme activity to the point where the enzymes become fully saturated with substrate. When an enzyme is saturated it has reach it max activity and max rate of reaction (Vmax). At this stage if you increase substrate conc further the rate will no longer change .

Question 14

What is the Km principle in relation to enzyme kinetics ?

Answer 14

• The higher the Km the weaker the binding.
• The lower the Km the stronger the binding.

Question 15

What are the two types of enzyme inhibitors ?

Answer 15

• Competitive
• Non-competitive

Question 16

What are enzyme co-factors ?

Answer 16

Some enzymes require cofactors (additional chemical components) for activity and they provide active sites/reactive groups.

Question 17

What are the two cofactor groups ?

Answer 17

• Essential ions
• Coenzymes

Question 18

What are holoenzymes ?

Answer 18

A complete functional enzyme which is catalytically active.

Question 19

What are apoenzymes ?

Answer 19

An enzymatically inactive protein part of an enzyme which requires a cofactor for its activity.

Question 20

What are the seven enzyme types (nomenclature) ?

Answer 20

1) Oxidoreductases
2) Transferases
3) Hydrolase
4) Lyases
5) Isomerases
6) Ligases
7) Translocases

Question 21

What is it called when an inactive enzyme, is in the absence of its essential cofactor?

Answer 21

Apoenzyme