You place cells in a solution of glucose and measure the rate at which glucose enters the cells. As you increase the concentration of glucose solution, the rate at which glucose enters the cells increases. However when the glucose concentration of the solution is increased above 10M, the rate at which glucose enters no longer increases. Which of the following is the most likely mechanism for glucose transport in the cells?

Options

A. Facilitated diffusion via a carrier protein
B. Facilitated diffusion without carrier protein
C. Active transport
D. Symport

Answer

To solve the question regarding the mechanism of glucose transport in cells, we can break it down into a series of steps:

### Step-by-Step Solution:

1. **Understanding the Experiment**:
- You place cells in a glucose solution and measure the rate of glucose entry into the cells as the concentration of glucose increases.

2. **Observing the Trend**:
- Initially, as the glucose concentration increases, the rate of glucose entry into the cells also increases. This indicates that the transport mechanism is responsive to changes in concentration.

3. **Identifying the Saturation Point**:
- When the glucose concentration exceeds 10M, the rate of glucose entry into the cells no longer increases. This plateau indicates that the transport mechanism has reached its maximum capacity.

4. **Analyzing Transport Mechanisms**:
- The increase in transport rate with concentration suggests a facilitated diffusion mechanism, where transport proteins (carrier proteins) help move glucose across the cell membrane.
- The saturation point indicates that all available carrier proteins are occupied at high concentrations, which is characteristic of facilitated diffusion.

5. **Eliminating Other Options**:
- Active transport would require energy and typically does not exhibit saturation in the same manner as facilitated diffusion.
- Simple diffusion does not involve carrier proteins and would not show saturation at high concentrations.
- Symport mechanisms involve the transport of two molecules together, which is not applicable here as only glucose is being transported.

6. **Conclusion**:
- The most likely mechanism for glucose transport in the cells, given the observed saturation at high concentrations, is facilitated diffusion via carrier proteins.

### Final Answer:
The most likely mechanism for glucose transport in the cells is **facilitated diffusion via carrier proteins**.

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