Question

The diagram given below represents a plant cell after being placed in a strong sugar solution. Study the diagram and answer the questions that follow:

(I) What is the state of the cell shown in the diagram?

(ii) Name the structure that acts as a selectively permeable membrane.

(iii) Label the parts numbered 1 to 4 in the diagram.

(iv) How can the above cell be brought back to its original condition? Mention the scientific term for the recovery of the cell.

Answer 1

(i) State of the cell shown in the diagram:

The state of the cell shown in the diagram is called plasmolysis or plasmolyzed cell.

Plasmolysis:

1. Plasmolysis is the withdrawal of the protoplasm of a plant cell from the wall due to the loss of water from the central vacuole by osmosis.
2. This occurs when the cells are placed in a hypertonic solution.
3. In the first instance when water loss begins from the cytoplasm and central vacuole, the protoplasm stops pressing the cell wall as turgor pressure becomes zero.
4. With the further loss of water, the contracting protoplasm first withdraws from the cell wall at the corners (incipient plasmolysis) and then shrinks from the cell wall except at one or more points. It is called evident or complete plasmolysis.
5. A cell cannot remain alive for long in this stage as protoplasm loses its functional efficiency. It leads to the death of the cells.
6. However, a freshly plasmolyzed cell placed in the hypotonic solution can regain its original form.

(ii) Selectively permeable membrane:

1. Selectively permeable membrane refers to a membrane that selectively allows different substances across the cell.
2. The cell membrane is the structure of the cell that acts as a selectively permeable membrane.

(iii) Labeling of Part 1-4:

1. Part 1: Cell wall- It is a completely permeable structure that is present only in plant cells.
2. Part 2: Hypertonic sugar solution- As the cell is placed in a hypertonic sugar solution, the exosmosis results in moving out of water and entry of the sugar solution inside the cell filling the empty space of the cell except for the shrunken protoplasm.
3. Part 3: Cell membrane- It is a selectively permeable membrane that allows only selective substances inside the cell.
4. Part 4: Nucleus- It is the cell organelle that contains genetic material.

(iv) Way to bring back the cell in its original condition:

1. We should place the cell in a hypotonic solution.
2. Then, water will enter the cell as now the osmotic concentration of the cell is higher than the surrounding.
3. So, the cell will again swell by the process of deplasmolysis.

Deplasmolysis:

1. It is the swelling of the protoplast of a plasmolyzed cell so that it comes in contact with the cell wall.
2. The cell regains its original volume.
3. Deplasmolysis can occur only if the freshly plasmolyzed cell is immediately placed in pure water or hypotonic solution.