Question
A contractile vacuole is an organelle that pumps excess water out of many bacterial cells. A bacterium was placed in solution A and observed to form contractile vacuoles at a rate of 11 per minute. The same bacteria was then placed in solution B and observed to form contractile vacuoles at a rate of 4 per minute. Based on this information, which of the following statements is correct?
Solution A is hyperosmotic to solution B
Solutions A and B are isosmotic.
Solution B is hyperosmotic to solution A.
Solutions A and B are isosmotic to a bacterial cell.
Solution A is hyperosmotic to solution B
Solutions A and B are isosmotic.
Solution B is hyperosmotic to solution A.
Solutions A and B are isosmotic to a bacterial cell.
Answers
GPT-4o mini
To determine the relationship between solutions A and B regarding their osmotic pressures, we need to analyze the rates at which the contractile vacuoles are forming in each solution.
In solution A, the bacterium forms contractile vacuoles at a rate of 11 per minute, indicating that it is pumping out excess water at a higher rate because it is likely in a hypotonic environment, where there is more water outside the cell than inside.
In solution B, the rate decreases to 4 per minute, suggesting that the osmotic pressure difference between the inside of the bacterium and the solution is less pronounced than in solution A. The lower rate indicates that there is still some excess water that needs to be expelled, but not as much as in solution A, which suggests solution B is either isotonic with the bacterial cell or is less hypotonic than solution A.
Given this information:
- If solution A is more hypotonic (more water outside), the bacterium would need to pump out more water (11 vacuoles/min).
- If solution B is less hypotonic or isotonic (less water outside), the bacterium would pump out less water (4 vacuoles/min).
Based on this reasoning, the following conclusions can be drawn:
1. **Solution A is hyperosmotic to solution B** - This is incorrect because a hyperosmotic solution would draw water into the bacterium, not cause it to pump more out.
2. **Solutions A and B are isosmotic** - This is also incorrect because the different rates of vacuole formation indicate different osmotic pressures.
3. **Solution B is hyperosmotic to solution A** - This is incorrect as well since that would imply solution A would have less water than solution B, resulting in the bacterium gaining water in solution B.
4. **Solutions A and B are isosmotic to a bacterial cell** - This is incorrect because the varying rates of contractile vacuoles suggest different osmotic environments.
From this analysis, the correct statement is:
**Solution A is hypotonic compared to solution B.**
However, this option is not explicitly presented in your choices. Thus, if insisting strictly on the provided choices without additional changes, none of the statements given in the question are correct.
In solution A, the bacterium forms contractile vacuoles at a rate of 11 per minute, indicating that it is pumping out excess water at a higher rate because it is likely in a hypotonic environment, where there is more water outside the cell than inside.
In solution B, the rate decreases to 4 per minute, suggesting that the osmotic pressure difference between the inside of the bacterium and the solution is less pronounced than in solution A. The lower rate indicates that there is still some excess water that needs to be expelled, but not as much as in solution A, which suggests solution B is either isotonic with the bacterial cell or is less hypotonic than solution A.
Given this information:
- If solution A is more hypotonic (more water outside), the bacterium would need to pump out more water (11 vacuoles/min).
- If solution B is less hypotonic or isotonic (less water outside), the bacterium would pump out less water (4 vacuoles/min).
Based on this reasoning, the following conclusions can be drawn:
1. **Solution A is hyperosmotic to solution B** - This is incorrect because a hyperosmotic solution would draw water into the bacterium, not cause it to pump more out.
2. **Solutions A and B are isosmotic** - This is also incorrect because the different rates of vacuole formation indicate different osmotic pressures.
3. **Solution B is hyperosmotic to solution A** - This is incorrect as well since that would imply solution A would have less water than solution B, resulting in the bacterium gaining water in solution B.
4. **Solutions A and B are isosmotic to a bacterial cell** - This is incorrect because the varying rates of contractile vacuoles suggest different osmotic environments.
From this analysis, the correct statement is:
**Solution A is hypotonic compared to solution B.**
However, this option is not explicitly presented in your choices. Thus, if insisting strictly on the provided choices without additional changes, none of the statements given in the question are correct.