Standard Answers For Enzyme Questions

Question 1

Rate of enzyme reactions at low temperatures?

Answer 1

— There is little kinetic energy
— The enzyme and substrate molecules move slowly
— There are few collisions between the enzyme and the substrate
— Few enzyme-substrate complexes form
— The rate of reaction is slow

Question 2

Rate of enzyme reactions when temperature is raised from low to medium?

Answer 2

— There is more kinetic energy
— The enzyme and substrate molecules move faster
— There are more collisions between the enzyme and substrate
— more enzyme-substrate complexes are formed
— The rate of reaction is faster

Question 3

Rate of enzyme reactions when the temperature is lowered from medium to low?

Answer 3

— There is less kinetic energy
— Enzyme and substrate molecules move slower
— There are less collisions between the enzyme and the substrate
— Less enzyme-substrate complexes are formed
— The rate of reaction is slow

Question 4

Rate of an enzyme reaction when the enzyme is kept at a high temperature (or raised from medium to high)?

Answer 4

— With time more hydrogen and ionic bonds break
— These bonds hold the tertiary structure of the enzyme
— So the enzyme changes shape/denatures with time
— The shape of the active site changes
— The substrate no longer fits into the active site
— Fewer enzyme-substrate complexes can form
— The rate of reaction is slower

Question 5

Rate of an enzyme reaction when the pH is too low or too high (different from optimum pH)

Answer 5

— The charge of the amino acids is changed
— This breaks hydrogen and ionic bonds
— These bonds hold the tertiary structure of the enzyme
— So the enzyme changes shape/denatures
— This changes the shape of the active site
— So the substrate can no longer fit/bind
— There are fewer enzyme-substrate complexes forming
— The rate of reactions is slower

Question 6

Rate of an enzyme reaction when the concentration of a substrate is increased?

Answer 6

— There are more collisions between the enzyme and the substrate
— There are more enzyme-substrate complexes forming
—The rate of reaction becomes faster

Question 7

Rate of an enzyme reaction when the concentration of substrate is saturating (very high)?

Answer 7

— All the active sites of the enzyme are occupied
— Adding more substrate will not increase the rate of reaction because there are no free active sites left to which the extra substrate can bind to
— The doesn’t increase any further

Question 8

Change in product concentrations as time goes by?

Answer 8

— The amount of product formed will level off over time
— Because the substrate is being used up
— So there are fewer/no collisions between the enzyme and the substrate
— So there are fewer/ no enzyme-substrate complexes formed

Question 9

Rate of an enzyme reactions when a competitive inhibitor is added?

Answer 9

— The inhibitor has a shape similar to the shape of the substrate
— The inhibitor will bind to the active site
— The inhibitor will prevent the substrate from binding (blocks the active site)
— There will be fewer enzyme-substrate complexes formed
— The rate of reaction will be lower

Question 10

Rate of an enzyme reaction when a non-competitive inhibitor is added?

Answer 10

— The inhibitor has a shape that is different from the shape of the substrate
— The inhibitor binds to the enzyme at a site away from the active site
— The binding of the inhibitor changes the shape of the active site
— The substrate no longer fits into the active site
— There will be fewer enzyme-substrate complexes
— The rate of reaction will be lower

Question 11

How does an enzyme speed up any reaction?

Answer 11

— Substrate binds to the active site
— Because it has a shape that is complementary to the shape of the active site
— Substrate binds to form the enzyme-substrate complexes
—The enzyme lowers the activation energy
— The chemical reaction occurs (i.e. substrate changes to product)
— The product no longer fits into the active site and is released