Name: Cell Membrane Transport
Uploaded: 2019-07-19
Duration: 10 min 50 s
Description: Substances move in and out of a cell through several different processes called membrane transport. Passive and active transport are two types of membrane transport.

Question

Describe fully what will occur if a plant cell is placed in a solution that has a higher water potential than the cell.

Use the following terms in your answer:
(cell wall, freely permeable, partially permeable, cell surface membrane, vacuole, tonoplast, cytoplasm, water potential, turgid, osmosis, protoplast, equilibrium)

Accepted Answer

Plant cells are surrounded by cell walls, primarily composed of cellulose. The cell wall is freely permeable as it allows a free exchange of water in and out of the cell. The cell wall is located just outside the plasma membrane. The plasma membrane of the plant is made up of a lipid bilayer. The plasma membrane or cell surface membrane in a plant cell is a partially or selectively permeable membrane as it regulates the exchange of specific molecules in and out of the cell.

A specific cell organelle in the plant called a vacuole is a large compartment that occupies a significant volume (up to 90%) of plant cells. The vacuole is enclosed by a membrane called tonoplast. Out of various other functions, one function of the vacuole is to maintain an internal acidic pH.

Water potential refers to the potential energy of water per unit volume relative to pure water in reference conditions. A solution with a higher water potential means it has a low solute concentration. We know that water moves from a solution having higher water potential than lower. Suppose a plant cell is placed in a solution that has a higher water potential than the cell. In that case, water will rush inside the cell cytoplasm through the freely permeable cell wall and partially permeable cell membrane by a process called osmosis.

Then water will diffuse inside the vacuole making its volume high. As the size of the vacuole increases, it pushes the content of the cell cytoplasm against the cellular membrane and places pressure (turgor pressure) on the cell wall. In a plant cell, the cell wall will resist the expansion of the protoplast (living part of the cell inside the plasma membrane), which causes the building up of pressure inside the cell. This pressure increases the water potential of the cell until the equilibrium is reached with the outside solution. The building up of the turgor pressure inside the cell makes it turgid.

Important Questions on Cell Membranes and Transport

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