` NH_(4)^(+)` is used to synthesise amino acids in plants. For it there are 2 main ways -
(i) `alpha-"Ketoglutaric acid"+NH_(4)^(+) +"NADPH" underset("Dehydrogenase")overset("glutamate ")to "glutamate"+H_(2)O+ "NADP"`
(ii) `R_(1)-underset(NH_(3)^(+))underset(|)overset(H)overset(|)C-COO^(-)+R_(2)-underset(O)underset(||)C-COO^(-) hArr R_(1)-underset(O)underset(||)C-COO^(-)+R_(2)-underset(NH_(3)^(+))underset(|)overset(H)overset(|)C-COO^(-)`

Options

A. Both (i) and (ii) are reductive amination
B. Both (i) and (ii) are transamination
C. (i) is transamination and (ii) is reductive amination
D. (i) is reductive amination and (ii) is transamination

Answer

To solve the question regarding the synthesis of amino acids in plants using the ammonium ion (`NH4+`), we will analyze the two main pathways described in the question.

### Step-by-Step Solution:

1. **Understanding the First Reaction**:
- The first reaction involves `alpha-Ketoglutaric acid`, `NH4+`, and `NADPH` in the presence of the enzyme `glutamate dehydrogenase`.
- The products of this reaction are `glutamate`, `H2O`, and `NADP`.
- This reaction is known as **reductive amination** because it involves the addition of an amine group (from `NH4+`) to a keto acid (`alpha-Ketoglutaric acid`), resulting in the formation of an amino acid (`glutamate`).

2. **Understanding the Second Reaction**:
- The second reaction involves an amino acid and a keto acid where the amino group is transferred.
- This process can be represented as the transfer of the amino group from one amino acid (e.g., `R1-NH3+`) to a keto acid (e.g., `R2-COO-`), resulting in a new amino acid and a new keto acid.
- This reaction is known as **transamination** because it involves the transfer of an amino group from one amino acid to another keto acid, forming a new amino acid.

3. **Identifying the Types of Reactions**:
- From the analysis above, we conclude that:
- The first reaction is **reductive amination**.
- The second reaction is **transamination**.

4. **Choosing the Correct Option**:
- Based on the identification of the reactions:
- Option 1 states both are reductive amination (incorrect).
- Option 2 states both are transamination (incorrect).
- Option 3 states the first is transamination and the second is reductive amination (incorrect).
- Option 4 states the first is reductive amination and the second is transamination (correct).

Thus, the correct answer to the question is **Option 4**.