Biological Reactions regulated by Enzymes

Question 1

Enzymes are…

Answer 1

Proteins

“Biological catalysts”

Question 2

Enzymes reduce…

Answer 2

Activation energy

Question 3

Catabolic reaction

Answer 3

Enzymes break things down

Question 4

Anabolic reaction

Answer 4

Enzymes build things up

Question 5

Metabolism

Answer 5

Series of enzyme reactions (catabolic and anabolic)

Question 6

Lock and key hypothesis

Answer 6

Enzyme = lock, active site = key hole, substrate = key
Substrate shape is complimentary to fit active site shape, successful collision between substrate and enzyme’s active site results in enzyme-substrate complex

Question 7

Induced fit hypothesis

Answer 7

Active site shape will change for substrate to fit

E.g Lysozyme (breaks down bacterial cell walls)

Question 8

Enzymes - temperature

Answer 8

As temp increases, rate of reaction increases. Once optimum temp is exceeded, enzyme denatures

Question 9

Enzyme is a protein

Answer 9

Has a tertiary structure - 3D globular structure held by disulphide bonds

Question 10

Factors that affect enzymes

Answer 10

Temperature, pH, enzyme concentration, substrate concentration

Question 11

Enzymes - pH

Answer 11

Small changes from optimum in pH causes inactivation (enzyme doesn’t work as well because H bonds disrupted)

Question 12

Enzymes - substrate concentration

Answer 12

Increasing concentration doesn’t affect reaction rate once point of saturation is reached
Increased concentration increased likelihood of successful collisions

Question 13

Enzyme - enzyme concentration

Answer 13

Increased enzyme concentration, increased rate (until all substrates saturated) - rate keep increasing if substrate in excess

Question 14

Enzyme inhibition

Answer 14

Inhibitors slow down enzyme rates of reaction/stop enzymes working completely

Question 15

Reversible reaction

Answer 15

Can be reversed, enzymes can function properly again

Question 16

Types of reversible reactions

Answer 16

Competitive and non-competitive

Question 17

Competitive e.g. Malonic acid

Answer 17

Competition for active site from substrate and inhibitor

Inhibitor blocks active site so no reaction can take place, when it leaves, active site is free to function

Question 18

Non-competitive e.g. Cyanide

Answer 18

Bonds with enzyme anywhere but active site

Inhibitor changes shape of active site

Question 19

Irreversible reaction

Answer 19

Enzyme destroyed and stopped from working e.g. Heavy metals

Question 20

Immobilised enzyme

Answer 20

Fixed in place (can’t move!)

Question 21

Advantages to using immobilised enzymes

Answer 21

• economically viable, enzymes reused easily
• easier to separate product at end
• easier to control rate of reaction
• enzyme less likely to denature (can use higher temperatures for faster rate)
• use a mixture of enzymes that wouldn’t normally work together

Question 22

Examples where immobilised enzymes are used in industry and medicine

Answer 22

To make lactose free milk

To make a ‘biosensor’ for blood/glucose or glucose oxidase

Question 23

How does a biosensor work?

Answer 23

Uses enzymes to detect specific molecules at low concentrations