5. Enzymes

Question 1

Describe Catalyst

Answer 1

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

Question 2

Describe Enzymes

Answer 2

Proteins that are involved in all metabolic reactions, where they function as biological catalysts

Question 3

Describe why enzymes are important in all living organisms in terms of a reaction rate necessary to sustain life

Answer 3

Maintains reaction speeds of all metabolic reactions (all the reactions that keep an organism alive) at a rate that can sustain life

Question 4

Describe the enzyme action

Answer 4

They’re specific to one particular substrate(s) as the enzyme is a complementary shape to the substrate

Question 5

Explain enzyme action with reference to: active site, enzyme-substrate complex, substrate and product

Answer 5

1. Enzymes and substrates randomly move about in solution
2. When an enzyme and its complementary substrate randomly collide and fit, an enzyme-substrate complex forms, and the reaction occurs.
3. A product (or products) forms from the substrate(s) which are then released from the active site. The enzyme is unchanged and will go on to catalyse further reactions.

Question 6

Explain the specificity of enzymes in terms of the complementary shape and fit of the active site with the substrate

Answer 6

• Specific as the active site of the enzyme is a complementary shape to the substrate (since its a protein with specific 3-D shape)
• Substrate moves into the enzyme’s active site -> Enzyme-substrate complex
• After the reaction has occurred: Products leave the enzyme’s active site and is free to take up another substrate

Question 7

Explain the effect of changes in temperature on enzyme activity in terms of kinetic energy, shape and fit, frequency of effective collisions and denaturation

Answer 7

• Increase of kinetic energy speeds up the molecules → frequency of collisions b/w the enzymes and substrates also increases
• Since more reactions occurs, more products are formed
• When the kinetic energy is higher than the optimum temperature, the enzyme goes through denaturation

Question 8

Explain the effect of changes in pH on
enzyme activity in terms of shape and fit and denaturation

Answer 8

• When the pH is too high or too low than the normal pH, the bonds break and therefore results to denaturation
• The active site of the enzyme loses its shape and so reduces the rate of enzyme activity