Question 16

Osmosis requires a selectively permeable membrane to produce a concentration gradient of solute.

A selectively permeable membrane allows only certain molecules to pass through while restricting others, which is essential for establishing the concentration gradient necessary for osmosis.

A) It prevents water from moving across it

This option is incorrect because a selectively permeable membrane does not prevent water from moving; rather, it permits the movement of water while restricting certain solutes. The key aspect of osmosis is that water moves toward a higher concentration of solute through the membrane.

B) It prevents osmotic pressure from increasing

This option is misleading. A selectively permeable membrane does not prevent osmotic pressure from increasing; instead, it allows for the development of osmotic pressure by enabling water to move in response to solute concentration differences. Thus, this choice does not accurately reflect the role of the membrane in osmosis.

C) It is necessary to produce a concentration gradient of solute

This option is correct because a selectively permeable membrane is crucial for creating and maintaining a concentration gradient. This gradient is what drives the movement of water during osmosis, as water moves from an area of lower solute concentration to an area of higher solute concentration.

D) It prevents hydrostatic pressure from increasing

This option is incorrect. The selectively permeable membrane does not inherently prevent hydrostatic pressure from increasing. Instead, the membrane facilitates the movement of water, which can actually lead to changes in hydrostatic pressure depending on the osmotic conditions.

Conclusion

The necessity of a selectively permeable membrane in osmosis lies in its role in establishing a concentration gradient of solute, which drives the movement of water. Options A, B, and D fail to capture the essence of this function, while C accurately describes the membrane's critical role in the osmosis process.