In a Human Cell

Question

In a human cell,
A)one enzyme usually catalyzes no more than five different chemical reactions.
B)nearly all chemical reactions are catalyzed by enzymes.
C)enzymes have to be constantly replaced as they are used up in the reactions that they catalyze.
D)some enzymes are specialized to store activation energy.

Accepted Answer

Enzymes are proteins that catalyze chemical reactions in cells, and nearly all chemical reactions in a human cell are catalyzed by enzymes. It is estimated that there are thousands of different enzymes in a single human cell, each catalyzing a specific reaction. Enzymes themselves are not used up in the reactions they catalyze, and do not have to be constantly replaced, although their activity can be regulated. There are no enzymes specialized for storing activation energy. The statement in option A is false, as some enzymes can catalyze many different reactions.