5. enzymes

Question 1

describe the term ‘catalyst’

Answer 1

substance that increases the rate of a chemical reaction and is not changed by the reaction

Question 2

describe the term ‘enzyme’

Answer 2

proteins that function as biological catalysts and are involved in all metabolic reactions

Question 3

explain enzyme action

Answer 3

substrate binds with the enzyme at the active site to form an enzyme-substrate complex (lock and key hypothesis) then reaction takes place at the active site to form the product, which separates from the enzyme, letting it catalyse another reaction

Question 4

explain the specificity of enzymes

Answer 4

• they are specialized proteins
• speed up chemical reaction
• remain chemically unchanged in the reactions so they can be used over and over again
• specific in action so they react with one type of substrate only
• they catalyze reversible reactions

Question 5

describe the effects of temperature on enzyme activity

Answer 5

increasing temperature up to optimum will increase the kinetic energy of enzyme and substrate molecules so that they move faster and collide more frequently therefore making products form more rapidly, if temperature is increased above optimum the kinetic energy increases so much that it breaks the hydrogen bonds, breaking the shape of the active site and the enzyme is said to be denatured

Question 6

describe the effects of pH on enzyme activity

Answer 6

when the pH fluctuates above or below the optimum, enzyme activity decreases. extreme changes in pH from the optimum break the bonds and the enzyme is said to be denatured

Question 7

what is the optimum pH in pepsin (stomach)

Answer 7

1-2 acidic

Question 8

what is the optimum pH in lipase (duodenum)

Answer 8

8-9 alkaline

Question 9

what is the optimum pH in salivary amylase (mouth)

Answer 9

7 neutral