Question

Briefly explain your observations in terms of osmosis and what you know about the structure of plant cells. Address the following points explicitly: • in comparing the Tap Water and Salt Water treatments to each other and to the No Treatment condition, whether there is an apparent change in the size of the cells, and why or why not • the net direction of water flow for each treatment • the net direction of solute flow for each treatment • the tonicity of Tap Water and Salt Water treatments

Answer 1

Answer 2

In this observation, we are likely looking at the effects of osmosis on plant cells. Osmosis is the movement of water across a semi-permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

1. Tap Water Treatment:

• Change in cell size: In the Tap Water treatment, the plant cells are likely to absorb water through osmosis, causing them to increase in size and become turgid. This is because the solute concentration outside the cells is lower than inside the cells, leading to a net movement of water into the cells.

• Net direction of water flow: Water flows into the cells from the surrounding Tap Water.

• Net direction of solute flow: There may be a small movement of solutes from the water into the cells, but it would be relatively negligible.

• Tonicity: The Tap Water treatment is hypotonic to the plant cells, as the solute concentration of the water is lower than that of the cell's cytoplasm.

2. Salt Water Treatment:

• Change in cell size: In the Salt Water treatment, the plant cells are likely to lose water through osmosis, causing them to shrink and become plasmolyzed. The saltwater has a higher solute concentration than the cells, leading to a net movement of water out of the cells.

• Net direction of water flow: Water flows out of the cells into the surrounding Salt Water.

• Net direction of solute flow: Some solutes from the plant cells may move into the surrounding Salt Water to balance the concentrations, but the primary effect is water loss from the cells.

• Tonicity: The Salt Water treatment is hypertonic to the plant cells, as the solute concentration of the water is higher than that of the cell's cytoplasm.

3. No Treatment (Control) Condition:

• Change in cell size: In the No Treatment condition, the plant cells are likely to maintain their normal size and shape. There should be no significant change in cell size.

• Net direction of water flow: Water may move in and out of the cells due to natural osmotic processes, but overall, there should be no net movement of water.

• Net direction of solute flow: Solute movement may occur to maintain equilibrium, but there should be no significant net solute flow.

• Tonicity: The No Treatment condition is isotonic to the plant cells, as the solute concentration is balanced, resulting in no net water movement.

In summary, osmosis plays a crucial role in the observed changes in cell size, water flow, solute flow, and tonicity of the plant cells under different treatments. The movement of water and solutes across the cell membrane is driven by differences in solute concentrations, leading to turgidity or plasmolysis of the cells in the Tap Water and Salt Water treatments, respectively. The No Treatment condition maintains cell size and shape due to the balanced tonicity.