2.1.4 Enzymes

Question 1

What are intracellular enzymes? Give an example

Answer 1

Enzymes that act within cells
E.g. catalase

Question 2

What are extracellular enzymes? Give an example

Answer 2

Enzymes that act outside of the cell
E.g. digestive enzymes amylase and trypsin

Question 3

What enzyme is needed to break down starch to maltose and where is it produced?

Answer 3

Amylase
Salivary glands and pancreas

Question 4

What enzyme is needed to break down maltose to glucose and where is it produced?

Answer 4

Maltase
Small intestine

Question 5

What is the normal temperature coefficient for enzyme controlled reactions?

Answer 5

Two

Question 6

What is temperature coefficient?

Answer 6

Measure of how much rate of reaction increases with a 10ºC change in temperature

Question 7

Explain the effects of increasing temperature on enzyme activity?

Answer 7

• Increased kinetic energy so more frequent successful collisions. Rate increases
• Optimum temperature reached. Highest rate of activity
• Bonds vibrate and break. Active site denatures as the tertiary shape changes

Question 8

What are the adaptations of enzymes in cold environments?

Answer 8

• More flexible structures
• Less stable
• Smaller temperature changes will denature it

Question 9

What are the adaptations of enzymes in hot environments?

Answer 9

• More stable
• More resistant to change as temperature rises

Question 10

What is the optimum pH for pepsin and where does it act?

Answer 10

pH 1-2
Stomach

Question 11

What is the optimum pH for trypsin, lipase and maltase and where does it act?

Answer 11

pH 8
Small intestine

Question 12

What happens when substrate concentration increases?

Answer 12

• Higher collision rate
• More enzyme-substrate complexes
• Reaches V_max
• Enzyme concentration becomes limiting factor

Same for increasing enzyme concentration, just substrate concentration becomes limiting factor

Question 13

What is V_max?

Answer 13

All of the active sites are occupied by substrates

Question 14

How to get a higher V_max on substrate concentration graph?

Answer 14

Increase concentration of enzyme to make more active sites available

Question 15

How does a competitive inhibitor work?

Answer 15

• Has similar shape to substrate
• Binds to active site temporarily
• Reduced substrates binding so rate of reaction decreases
• V_max remains same as increasing substrate concentration can overcome effects

Question 16

How does a non-competitive inhibitor work?

Answer 16

• Binds to allosteric site
• Tertiary structure changes
• Active site no longer complementary to substrate
• Lower V_max as increasing substrate concentration cannot overcome effects

Question 17

What is end product inhibition?

Answer 17

• Product of reaction inhibits the enzyme
• Negative feedback
• Ensures resource are not wasted
• Non-competitive inhibition

Question 18

What is a cofactor?

Answer 18

Non-protein molecule which helps enzymes carry out their function

Question 19

What is a coenzyme?

Answer 19

A cofactor that is an organic molecule

Question 20

Where are inorganic cofactors derived from? Give example

Answer 20

Minerals
E.g. Chloride on amylase

Question 21

Where are coenzymes derived from? Give example

Answer 21

Vitamins
E.g. Vitamin B3 to synthesise NAD

Question 22

What are prosthetic groups? Give example

Answer 22

Cofactors which are permanently bound to a protein
E.g. Zinc ions in carbonic anhydrase

Question 23

What is precursor activation?

Answer 23

Inactive enzymes undergo a change in tertiary structure to be activated. Normally by:
- Addition of a cofactor
- Action of another enzyme
- Changes in conditions