Protein which transports glucose into cells is

Options

A. Trypsin
B. Keratin
C. Haemoglobin
D. GLUT-4

Explanation

To determine the protein that transports glucose into cells, we can analyze the given options one by one:

1. **Trypsin**: This is an enzyme that plays a crucial role in the digestion of proteins. It helps break down proteins into smaller peptides in the digestive system. Therefore, it is not involved in glucose transport.

2. **Keratin**: This is a structural protein found in hair, nails, and skin. It provides strength and protection but does not have any role in transporting glucose into cells.

3. **Hemoglobin**: This is a protein found in red blood cells (RBCs) that is primarily responsible for transporting oxygen from the lungs to the rest of the body. While it is an important protein, it does not transport glucose.

4. **GLUT4**: This is a glucose transporter protein that plays a significant role in the uptake of glucose into cells, especially in muscle and fat tissues. GLUT4 is regulated by insulin, which facilitates its translocation to the cell membrane, allowing glucose to enter the cells.

Based on the analysis of the options, the correct answer is **GLUT4**, as it is the protein specifically responsible for transporting glucose into cells.

### Step-by-Step Solution:
1. Identify the options provided: Trypsin, Keratin, Hemoglobin, GLUT4.
2. Analyze each option:
- Trypsin: Enzyme for protein digestion, not glucose transport.
- Keratin: Structural protein, not involved in glucose transport.
- Hemoglobin: Oxygen transport protein, not involved in glucose transport.
- GLUT4: Glucose transporter, responsible for glucose transport into cells.
3. Conclude that the protein which transports glucose into cells is **GLUT4**.