Which of the following element is present in insulin ?

Options

A. Sodium
B. Zinc
C. Lithium
D. Iron

Explanation

To determine which element is present in insulin, we will analyze each of the provided options: sodium, zinc, lithium, and iron.

### Step-by-Step Solution:

1. **Understanding Insulin**: Insulin is a peptide hormone produced by the pancreas that regulates glucose levels in the blood. It is important to know the components and elements that are involved in its structure and function.

2. **Analyzing the Options**:
- **Sodium (Na)**: Sodium is primarily involved in maintaining fluid balance and is not a component of insulin.
- **Zinc (Zn)**: Zinc plays a crucial role in the stabilization of insulin. It is known to be involved in the storage of insulin in the pancreas and helps in the formation of insulin hexamers, which are essential for its proper function.
- **Lithium (Li)**: Lithium is used as a medication for mood disorders and does not have a role in insulin.
- **Iron (Fe)**: Iron is essential for the production of hemoglobin in red blood cells and is not a component of insulin.

3. **Conclusion**: Among the given options, zinc is the only element that is present in insulin. It is important for the stabilization and storage of insulin in the pancreas.

### Final Answer:
The element present in insulin is **Zinc (Zn)**.