Which statement about the binding of enzymes and substrates is correct?
a. substrate molecules bind to the active site of the enzyme only by weak bonds, such as hydrogen bonds or hydrophobic attraction.
b. substrate molecules fit into the active site of an enzyme like a key fits into a lock.
c. when substrate molecules bind to the active site of the enzyme, the enzyme undergoes a slight change in shape.

Answers a. and c. should be correct.

Explanation:

Enzymes help increase the rate in which a chemical reaction occurs. The interactions between the enzyme and the substrate induced conformational changes in the enzyme that facilitate and strengthen the binding with its substrate. That is called the induced fit model. Before this model, scientists explain the binding of enzyme and substrate as a “lock-and-key”. There are four type of weak interactions by which enzymes and substrates bind each other: 1) hydrogen bonds, 2) electrostatic interactions, 3) hydrophobic interactions and 4) van der Waals interactions. The strong binding between the enzyme and its substrate is the addition of several weak interactions working together.