19. Enzymes

Match each model with correct descriptions: (a) Induced fit model, (b) Lock and key model.

________ Active site undergoes changes in shape during reaction.

________ Enzyme is specific only to one substrate.

________ Shape of active site is similar to that of substrate. 

________ Enzyme model that more accurately describes substrate-enzyme interactions.

What is the difference between the lock-and-key model of enzyme action and the induced-fit model?

Why is the induced-fit model a more likely model than the lock-and-key model?

Match the terms (1) active site, (2) lock-and-key model, and (3) induced-fit model with each of the following:

a. the portion of an enzyme where catalytic activity occurs

A patient arrives in an emergency department complaining of chest pains. What enzymes would you test for in the blood serum?

How would the lock-and-key model explain that sucrase hydrolyzes sucrose, but not lactose? (16.4)

If a blood test indicates a high level of ALT, what could be the cause? (16.4)

b. How is the active site different from the whole enzyme structure?

b. After the products have formed, what happens to the enzyme?

What are isoenzymes?

How is the LDH isoenzyme in the heart different from the LDH isoenzyme in the liver?

What kind of interaction attracts the cofactor Mg²⁺ and ATP to each other? (Hint: Look at the structure of the phosphate group.)

Match the terms (1) active site, (2) lock-and-key model, and (3) induced-fit model with the following descriptions:

a. the portion of an enzyme where catalytic activity occurs

b. the active site adapts to the shape of a substrate

c. the active site has a rigid shape

Do the amino acids that are in the active site of an enzyme have to be near each other in the enzyme’s primary structure? If no, explain.

ALlied Health The enzyme trypsin catalyzes the breakdown of many structurally diverse proteins in foods. Does the induced-fit or lock-and-key model explain the action of trypsin better? Explain.

ALlied Health The enzyme sucrase catalyzes the hydrolysis of the disaccharide sucrose but not the disaccharide lactose. Does the induced-fit or lock-and-key model explain the action of sucrase better? Explain.