Biology [3 marks Question Answer]

(a) A cell in normal turgid condition
(b) - (d) Successive stages in shrinkage of protoplasm from the cell well after being placed in a hypertonic solution. Diagrammatic representation of plasmolysis in a cell

(i) Water is major component of protoplasm.
(ii) It is an important raw material for photosynthesis.
(iii) Most metabolic and enzymatic reactions take place in the presence of water.

(i) The root hair represents a large surface area in contact with the soil particle.
(ii) The minute root hair can penetrate between the soil particles and when it comes in contact with soil water, the cell membrane allows efficient entry of water into the root.
(iii) The cytoplasm and the vacuoles also help in this water absorption by osmosis.

(1) The process is called osmosis.
(ii) This process occurs in the root hair cells of plants.
(iii) The solution placed inside the dialysis tubing is generally strong sugar solution or salt solution.
(iv) The level of the solution in the capillary tube rises above the original level.
(v) Osmosis is a physiological process where the water molecules or solvent molecules move through a semi-permeable membrane from a solution having a higher concentration of solvent molecules to the solution having a lower concentration of water or solvent molecules.

(i) Put the cell back into the drop of water for sometime. Deplasmolysis occurs.
(ii) Plasmolysis.
(iii) Plasmolysed cell.

(i) The process of osmosis.
(ii) Osmosis is a special type of diffusion of solvent molecules through a semi-permeable membrane from a region of their higher concentration to the lower concentration region, but not vice versa.
(iii) The level of water in column A will rise along with the passage of time and will ultimately stop when the concentration of water molecules are equal on both sides of the membrane.
(iv) (a) Parchment paper, (b) Egg membrane.
(v) Solution A.
(vi) It permits the movement of only water molecules to pass through it.

(i) 1. Nucleus
2. Vacuole
3. Cell wall
4. Cell membrane
(ii) Part 4 is the cell membrane. It is semi-permeable. It allows only water molecules to pass through it.
(iii) Because it is an extension of epiblema cell.
(iv) By the addition of fertilizer, root hair becomes flaccid, because water will move out of it as soil water becomes hypertonic.

(i) 1. Vacuole (containing cell sap)
2. Soil particles
3. Xylem vessel
4. Cortex cells
5. Vacuole in cortical cells
(ii) Root hair cell is unicellular
(iii) See diagram alongside.
(iv) Osmosis
(v) Osmotic pressure
(vi) This pressure is set up due to the difference in osmotic gradient.

(i) Flaccid.
(ii) Plasma membrane.
(iii) If the cell had been placed in distilled water it remains in a fully distended condition. Its plasma membrane remains in close contact with the cell wall and presses against it.
(iv) Chloroplast will be present in the protoplasm outside the vacuole.
(v) Cell wall.

(i) Plasmolysis
(ii) Hypertonic solution
(iii) (1) Nucleus, (2) Sugar drops, (3) Small vacuole, (4) Large vacuole.
(iv) Plant cell (1) Presence of cell wall, (2) Presence of large vacuole.
(v) It has to be placed in a hypotonic solution.

(i) 1-Nucleus. 2-Cell wall. 3-Cytoplasm of the root hair cell.
(ii) 1. Water: Carries minerals to the plant.
2. Minerals: They are needed for healthy plant growth.
(iii) Osmosis.
(iv) In the Fig. A, the root hair has to pass through the soil particles, and as such, they are not straight. In the Fig. B, the root hair has no obstruction in water, and as such it grows straight.

(i) The phloem has been removed in the part of the ring. The food prepared by leaves comes down through phloem, but since the phloem is cut off, the food gets collected in the upper part of the ring and hence the swelling appears.
(ii) The food prepared by leaves is not able to pass on downward as the phloem has been removed, resulted in the shrinking of the bark.
(iii) Phloem.
(iv) Xylem.
(v) Bark protects the attack of fungi and insects, against loss of water by evaporation and against variation of external temperature and loss of water due to evaporation.

(i) The size of the holes in the membrane is large enough to allow only the solvent particles to pass through it. But solute particle cannot pass through it. Thus, the membrane acts as the semi-permeable.
(ii) Solvent molecules will pass through the membrane in both directions. Since solvent molecules are present on both the sides they will strike the semi-permeable membrane and pass through the same.
(iii) There is a net movement of solvent molecules from the place of its higher chemical potential to the place of its lower chemical potential, i.e., from right to left.

(i) To demonstrate the role of xylem and phloem in flowering plants.
(ii) In the shoot, A phloem tissue has been removed. In shoot B central xylem tissue has been removed.
(iii) Plant A gets water and minerals and synthesizes its food and remains healthy. Plant B due to lack of xylem does not get its supply of water and minerals. The leaves are seen drooping and will dry.

(i) Exosmosis (exit of water) has resulted in the shrinkage of the protoplasm of cell B.
(ii) Plasmolysis and deplasmolysis.
(iii) When plant cells are kept in a hypertonic solution, exosmosis takes place. This process is called plasmolysis.
(iv) Hypertonic solution.
(v) The cell in B can be brought back to its original condition by placing it in a drop of distilled water.
(vi) 1. Cell wall, 2. Plasma membrane, 3. Chloroplast.

(i)
Solution 1 – Hypotonic solution
Solution 2 – Hypertonic solution
Solution 3 – Isotonic solution
(ii) In beaker three, the solution present is an isotonic solution, i.e. the relative concentration of water molecules and solutes is same in the solution as well as inside the cell. There is no movement of water molecules across the cell membrane. Hence, the size of the potato cubes remains same.
(iii) The cell sap of root hairs has higher concentration of solute than the surrounding water.
(iv) Osmosis is the diffusion of water molecules across the semi-permeable membrane from the region of dilute solution (i.e. a lower solute concentration) to the region of concentrated solution (i.e. a higher solute concentration).
(v) The cell wall is freely permeable to all the substances, while the cell membrane is selectively permeable and allows only certain substances to enter or exit the cell.

(i) Osmosis.
(ii) Transfer of water or solvent molecules from a solution of lower concentration to a solution of higher concentration through a semi-permeable membrane is called osmosis.
(iii) The level of sugar solution rises in the stem of thistle funnel, whereas the water level in the beaker falls.
(iv) A non-permeable membrane can be used in place of parchment paper for a control experiment.
(v) (1) Root hair cell sap corresponds to concentrated sugar solution.
(2) Cell membrane of root hair cell corresponds to parchment paper.
(3) Soil solution corresponds to water in the beaker.
(vi) Goat’s bladder or pig’s bladder.
(vii) (1) Helps in water absorption.
(2) Helps in stomatal opening and closing thus facilitating gaseous exchange.