Glucagon produced by `alpha`-cells of islets of Langerhans

Options

A. Converts glucose to glycogen
B. Converts glycogen to glucose
C. Decreaseds concentration of glucose in blood
D. None of these

Answer

**Step-by-Step Solution:**

1. **Identify the Source of Glucagon**: Glucagon is produced by the alpha cells of the islets of Langerhans, which are located in the pancreas.

2. **Understand the Function of Glucagon**: The primary function of glucagon is to increase blood glucose levels. It does this by promoting the conversion of glycogen (stored glucose) into glucose.

3. **Explain the Process**: When glucagon is released into the bloodstream, it signals the liver to convert glycogen into glucose through a process called glycogenolysis. This process increases the concentration of glucose in the blood, leading to a state known as hyperglycemia.

4. **Evaluate the Options**:
- **Option 1**: Converts glucose to glycose - Incorrect, as glucagon does not convert glucose to glycose.
- **Option 2**: Converts glycogen to glucose - Correct, as this is the primary function of glucagon.
- **Option 3**: Decrease concentration of glucose in blood - Incorrect, as glucagon increases glucose levels.
- **Option 4**: None of these - Incorrect, since option 2 is correct.

5. **Conclusion**: The correct answer is that glucagon produced by alpha cells converts glycogen to glucose, leading to an increase in blood glucose concentration.