2.9.1 Enzyme Action: The Induced-Fit Model

Question 1

catalysts

Answer 1

• Enzymes are proteins that serve as catalysts. Catalysts speed up or slow down reactions, but remain unchanged

Question 2

induced-fit model

Answer 2

• a model for enzyme action

Question 3

The mechanism for enzymatic action helps to explain the characteristics of enzymes:

Answer 3

• Enzymes work better as the temperature increases because molecules move faster. The enzyme quits working if the temperature gets too high because the enzyme denatures, or loses its conformational shape.
• The pH can affect the enzyme by causing the active site of the enzyme to change shape.
• Certain chemicals enhance the action of enzymes. Cofactors are molecules that an enzyme requires to work. Many vitamins are cofactors.
• Some chemicals slow down or inhibit enzymes:
- A competitive inhibitor can compete with the substrate for the active site.
- A noncompetitive inhibitor can bind to a different part of the enzyme permanently and stop enzyme function.

Question 4

active site

Answer 4

• the place where the substrate (the reactant molecule)

fits

Question 5

induced-fit hypothesis

Answer 5

• The substrate comes into contact with the active site, and the active site induces a fit around the substrate

Question 6

catalytic cycle

Answer 6

• the enzyme mechanism. The substrate fits into the active site of the enzyme. The bond is broken, the
  products are released, and the enzyme remains intact.

Question 7

Enzyme specificity appears to be a function of the enzyme’s

Answer 7

• active site

Question 8

Enzymes bind to particular substrates because

Answer 8

• the shape and charge of the active site is complementary to the substrate

Question 9

True or false?

The active site is a rigid pocket in the enzyme that is perfectly shaped to match the shape of the substrate molecule.

Answer 9

• false

Question 10

Non-enzymatic molecules that are close in shape to the enzyme substrate, but are non-reactive, are

Answer 10

• competitive inhibitors

Question 11

The specificity of the active site of an enzyme is determined by the

Answer 11

• amino acid sequence