Enzymes act as catalysts in living organisms. What type of macromolecules are enzymes?

A. Carbohydrates
Incorrect. Carbohydrates serve as a major energy source in the diet of animals.

B. Nucleotides
Incorrect. Nucleotides form the basic constituent of DNA and RNA.

C. Proteins
Correct!

D. Lipids
Incorrect. Lipids serve as an energy source and constitute one of the principal structural materials of living cells.

Living organisms require enzymes for most of their metabolic processes. Which of the following characteristics about enzymes is not true?

A. Enzymes are non-reusable
Correct! Enzymes are not used up in the reactions they catalyze and can be used over and over.

B. Enzymes are catalysts
Incorrect. Enzymes catalyze chemical reactions.

C. Enzymes are proteins
Incorrect. Enzymes are made up of proteins.

D. Enzymes contain an active site.
Incorrect. Enzymes contain an active site to which the substrate attaches.

The diagram below represents the steps in the hydrolysis of a molecule of sucrose.

In this diagram, structure X represents the —

A. the substrate
Incorrect. The substrate is what is changed by the enzyme.

B. the inhibitor
Incorrect. An inhibitor slows or stops a reaction.

C. the enzyme
Correct!

D. the product
Incorrect. The product is what results from the chemical reaction.

Lactose is a complex sugar made up of the simpler sugars Glucose and Galactose. What enzyme would catalyze the hydrolysis reaction that produces Glucose and Galactose?

A. Maltase
Incorrect. Maltase breaks down maltose.

B. Protease
Incorrect. Protease breaks down proteins.

C. Lactase
Correct!

D. Lipase
Incorrect. Lipase breaks down lipids.