Final answer:
A protein cofactor is required for holoenzyme function. Coenzymes like coenzyme A (CoA), NADH, and ATP play a vital role in enzyme activation.
Step-by-step explanation:
The correct answer is Option B) a protein cofactor
A protein cofactor is required for holoenzyme function. A holoenzyme is formed when a cofactor or coenzyme binds to the enzyme's active site, activating the enzyme.
For example, some cofactors and coenzymes like coenzyme A (CoA) bind to the enzyme's active site, aiding in the chemistry of the transition of a substrate to a product. NADH and ATP are also examples of commonly used coenzymes that provide high-energy electrons or phosphate groups, respectively, which bind to enzymes, thereby activating them.