Which is a coenzyme

Options

A. Protein
B. `NAD^(+)`
C. Zinc
D. Copper.

Answer

To determine which option is a coenzyme, let's analyze each option step by step:

### Step 1: Understand what a coenzyme is
Coenzymes are organic non-protein molecules that assist enzymes in catalyzing biochemical reactions. They are often derived from vitamins and play a crucial role in metabolic processes.

**Hint:** Remember that coenzymes are not proteins; they are organic molecules that help enzymes.

### Step 2: Evaluate the first option - Protein
Proteins are large, complex molecules made up of amino acids. They serve various functions in the body, including acting as enzymes, but they are not coenzymes.

**Hint:** Coenzymes are not proteins; they are distinct from enzymes.

### Step 3: Evaluate the second option - NAD+
NAD+ (Nicotinamide adenine dinucleotide) is indeed a coenzyme. It is derived from niacin (vitamin B3) and plays a significant role in oxidation-reduction reactions in cellular metabolism.

**Hint:** Look for organic molecules that assist enzymes and are derived from vitamins.

### Step 4: Evaluate the third option - Zinc
Zinc is a metal ion and is classified as a cofactor, not a coenzyme. Cofactors can be metal ions or organic molecules that assist enzymes but are not classified as coenzymes.

**Hint:** Remember that metal ions are not coenzymes; they are cofactors.

### Step 5: Evaluate the fourth option - Copper
Like zinc, copper is also a metal ion and serves as a cofactor. It does not fit the definition of a coenzyme.

**Hint:** Again, metal ions do not qualify as coenzymes.

### Conclusion
Based on the evaluations, the only option that fits the definition of a coenzyme is NAD+. Therefore, the correct answer is:

**Correct Answer:** Option 2 - NAD+