Enzymes Rate Of Reaction

Question 1

How does enzymes concentration affect the rate of reaction?

Answer 1

As the concentration of the enzyme increases, the rate of reaction increases.
—> more enzymes-substrate complexes form as more enzymes are added
—> reaction eventually stops as substrate is used up

Question 2

How does substrate concentration affect the rate of reaction?

Answer 2

1. Rate of reaction is limited by the substrate concentration
   —> more substrate is added, more ES complexes form, so rate of reaction increases
2. Rate slows down to a constant rate
   —> fixed number of active sites are fully saturated by substrate molecules, so enzyme concentration is now the limiting factor

Question 3

How does temperature affect the rate of reaction?

Answer 3

1. As the temperature increases, the rate of reaction increases
   —> more kinetic energy, so more collisions, forming more ES complexes
2. At the optimum temp, molecules have max kinetic energy so fastest rate of reaction
   —> highest collisions, so most ES complexes form
3. As the temperature rises above the optimum, the rate of reaction decreases
   —> enzymes begin to denature, increasing kinetic energy breaks R-groups, so specific tertiary shape changes, so is no longer complementary to the substrate, so no ES complexes form

Question 4

How does pH affect the rate of reaction?

Answer 4

1. The more H+ ions, the more the shape changes, the lower the rate of reaction
   —> low pH causes enzyme to denature, so no ES complexes form
2. At the optimum pH, the rate of reaction is the fastest
   —> enzymes has a complementary shape, so most ES complexes form
3. High pH causes a low rate of reaction
   —> enzymes denature as active site shape changes, so no ES complexes form

Question 5

How do competitive inhibitors affect the rate of reaction?

Answer 5

• inhibitor molecule is similar in shape to the substrate
• compete with the substrate for the active site
• inhibitor binds to the active site and prevent substrate from binding
• so some ES complexes will form but at a much slower rate

—> inhibition can be reduced by increasing substrate concentration as substrate is more likely to bind to the active site rather than the inhibitor

Question 6

How do non-competitive inhibitors affect the rate of reaction?

Answer 6

• inhibitor is different shape than the substrate
• binds to an allosteric site on the enzyme molecules
• breakers hydrogen and ionic bonds in the enzymes tertiary structure
• tertiary structure and active site changes shape
• substrate is no longer complementary to the active site so does not bind
• ES complexes can no longer form

—> enzymes are permanently denatured

Question 7

What is a non-competitive activator?

Answer 7

• bind to allosteric site on the enzyme
• changes the tertiary structure
• active site becomes more complementary

—> increases rate of reaction