Consider the following:
1. Succinate 2. Succinyl CoA
3. `NADH + H^+` 4. `CO_2`
When `alpha`-ketoglutarate dehydrogenase enzyme acts on `alpha`-ketoglutarate, which of the above are produced?

Options

A. 1 and 2 only
B. 1 and 3 only
C. 1, 3 and 4
D. 2, 3 and 4

Answer

To solve the question regarding the products formed when the enzyme alpha-ketoglutarate dehydrogenase acts on alpha-ketoglutarate, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction**: The reaction in question occurs in the citric acid cycle (Krebs cycle), where alpha-ketoglutarate is converted into succinyl CoA.

2. **Enzyme Involved**: The enzyme that catalyzes this reaction is alpha-ketoglutarate dehydrogenase.

3. **Reactants and Products**:
- The substrate (reactant) is alpha-ketoglutarate.
- The products of this reaction include:
- Succinyl CoA
- NADH + H⁺ (reduced form of NAD⁺)
- CO₂ (carbon dioxide)

4. **Analyzing the Options**:
- **Succinate**: This is not produced in this step of the cycle.
- **Succinyl CoA**: This is produced.
- **NADH + H⁺**: This is produced as NAD⁺ is reduced.
- **CO₂**: This is released as a byproduct of the decarboxylation process.

5. **Conclusion**: The products formed when alpha-ketoglutarate dehydrogenase acts on alpha-ketoglutarate are:
- Succinyl CoA (2)
- NADH + H⁺ (3)
- CO₂ (4)

Thus, the correct answer is options 2, 3, and 4.

### Final Answer:
The products formed are:
- Succinyl CoA (2)
- NADH + H⁺ (3)
- CO₂ (4)