Suppose an enzyme and its substrate obey the lock and key model of enzyme catalysis. Which of the following would be true of the enzyme? a. only one substrate could be converted to product by the enzyme
b. the active site of the enzyme must be rigid
c. the entire enzyme must be rigid
d. the active site of the enzyme must be flexible
e. the enzyme could bind different substrates if the substrates shared a common motif somewhere in their structures

only one substrate could be converted to product by the enzyme

Explanation:

If an enzyme obeys the lock and key model, it then follows that the design of the enzyme is unique to a particular substrate.

Just as only the correct key can effectively fit into a lock, only the appropriate substrate whose design matches that of the enzyme can fit into the enzyme.

Owing to the lock and key model of enzyme activity, only one enzyme could interact with a substrate to yield particular product.