2.5 Enzymes

Question 1

Enzyme

Answer 1

a globular protein which acts as a biological catalyst by speeding up the rate of a chemical reaction

Question 2

Active site

Answer 2

the region on the surface of the enzyme which binds to the substrate molecule

Question 3

Where do enzyme reactions often occur?

Answer 3

aqueous solutions

Question 4

Describe the process of enzyme catalysis

Answer 4

1. a substrate binds to the enzyme’s active site forming the enzyme-substrate complex
2. the enzyme catalyses the conversion of the substrate into a product, creating a enzyme-product complex
3. the enzyme and product dissociate
4. the enzyme then continues to catalyses further reactions

Question 5

How to increase the frequency of collisions in enzyme catalysis?

Answer 5

increase the molecular motion of the particles (thermal energy to increase kinetic energy)
increase the concentration of particles

Question 6

What modifies enzyme structure?

Answer 6

temperature

pH

Question 7

How can an enzyme structure be affected?

Answer 7

high temperatures and extreme pH disrupt chemical bonds that maintain the tertiary structure of the enzyme
changes the active site (denaturation) can prevent the enzyme’s capacity to bind the substrate

Question 8

What factors may affect rate of activity of enzymes?

Answer 8

temperature
pH
substrate concentration

Question 9

How does temperature affect rate of enzyme activity?

Answer 9

low temperatures - insufficient thermal energy for the activation of an enzyme-catalysed reaction to preceed
higher temperatures - increase the speed and motion of both enzyme and substrate -> higher enzyme activity
optimal temp - highest rate of reaction
higher temperatures - enzyme’s hydrogen bonds are disrupted and thus denaturation

Question 10

How does pH affect rate of enzyme activity?

Answer 10

charge of enzyme will be altered, which will alter protein solubility and overall shape
change the shape or charge of active site will diminish its ability to bind the substrate
optimal pH - moving outside of this will diminish enzyme activity

Question 11

How does substrate concentration affect rate of enzyme activity?

Answer 11

more substrates = increased chance of enzyme and reacting within a given period
after a certain point, the rate of activity will cease to rise regardless of any further increases in substrate levels

Question 12

What are the factors to test the effect of factors affecting enzyme activity?

Answer 12

which factor to investigate (temp/concentration/pH)
which enzyme/substrate to use
how to measure enzyme activity

Question 13

What are independent variables that can be chosen from?

Answer 13

temperature
pH
substrate concentration
presence of inhibitor

Question 14

Examples of common enzyme-catalysed reactions:

Answer 14

1. catalase - hydrogen peroxide - oxygen + water
2. pepsin - protein - short polypeptides
3. diastase - starch - maltose

Question 15

What are ways to measure enzyme activity?

Answer 15

gas production
digestion of a solid
digestion of a liquid
colour change

Question 16

Ways to measure gas production

Answer 16

count bubbles
gas syringe with increasing volume of gas
pressure change in sealed environment (data logger)

Question 17

Ways to measure digestion of a solid

Answer 17

calculate % weight change
change in diameter
volume of liquid produced

Question 18

Ways to measure digestion of a liquid

Answer 18

diffusion out of dialysis tube

Question 19

Ways to measure colour change

Answer 19

starch reacts with iodine (purple colour)
peptide bonds are stained via the Biuret test
reducing vs non reducing sugars

Question 20

What are immobilised enzymes used for?

Answer 20

biofuels
medicine
biotechnology
food production
textiles
paper

Question 21

How is lactose-free milk produced?

Answer 21

the enzyme lactase is purified from yeast or bacteria and then bound to an inert substance
milk is then repeatedly passed over this immobilised enzyme, becoming lactose-free

Question 22

What are some advantages of lactose-free dairy products?

Answer 22

a source of dairy for lactose-intolerant individuals
increase sweetness in the absence of artificial sweeteners
reduce crystallisation of ice creams
reducing production time for cheeses and yogurts