Terminology check: the active form of an enzyme that includes its protein part and any required cofactor is called the:

Introduction / Context:
Many enzymes require non-protein components to function. These may be metal ions or organic coenzymes. The combined active complex has a specific name that distinguishes it from the protein portion alone.

Given Data / Assumptions:

• A protein portion (apoenzyme) may be inactive by itself.
• Cofactors can be metal ions or organic molecules (coenzymes or prosthetic groups).
• The active catalytic entity includes both parts.

Concept / Approach:
The holoenzyme is the complete, catalytically active enzyme comprising the apoenzyme plus its necessary cofactor(s). The apoenzyme alone lacks full catalytic activity. A coenzyme is the organic cofactor component and is not the complete catalytic complex by itself.

Step-by-Step Solution:

Verification / Alternative check:
Enzyme assays often show no activity until cofactors are supplied, confirming that only the holoenzyme is catalytically competent.

Why Other Options Are Wrong:
Apoenzyme: Protein alone, typically inactive. Coenzyme: Organic cofactor only, not the full catalytic entity. None of these: Incorrect because the proper term exists.

Common Pitfalls:
Using “coenzyme” and “cofactor” interchangeably with “holoenzyme”; remember holoenzyme refers to the complete active complex.

Final Answer:
holoenzyme