Biology
A candidate in order to study the process of osmosis has taken 3 potato cubes and put them in 3 different beakers containing 3 different solutions. After 24 hours, in the first beaker the potato cube increased in size, in the second beaker the potato cube decreased in size and in the third beaker, there was no change in the size of the potato cube. The following diagram shows the result of the same experiment.
(a) Give the technical terms of the solutions used in the beakers 1, 2 and 3.
(b) In beaker 3, the size of the potato cube remains the same. Explain the reason in brief.
(c) Write the specific features of the cell sap of root hairs which helps in absorption of water.
(d) What is osmosis?
(e) How does a cell wall and a cell membrane differ in their permeability?
Roots Absorption
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Answer
(a) Solution 1 → Hypotonic solution
Solution 2 → Hypertonic solution
Solution 3 → Isotonic solution
(b) In beaker 3, the solution present is an isotonic solution, i.e. the relative concentration of water molecules and solutes is the 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 potato cube remains the same.
(c) The cell sap of root hair has a higher concentration of salts as compared to the outside soil water.
(d) Osmosis is the movement of water molecules from their region of higher concentration (dilute solution or with a lower solute concentration) to their region of lower concentration (concentrated solution or with a higher solute concentration) through a semi permeable membrane.
(e) The cell wall is freely permeable. It allows the movement of water molecules and dissolved substances freely in and out of the cell. The cell membrane is semi permeable. It allows water molecules to pass through but not the larger molecules of the dissolved salts.
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Related Questions
Three cylinders of potato were carefully dried on a blotting paper and weighed. Each piece weighed 3 grams. Each one was placed in the beaker as shown below:
Answer the following questions:
(a) After 48 hours, which potato cylinder would be the heaviest?
(b) The movement of which substance is mainly responsible for the weight change in the potato cylinders?
(c) Name and define the process which is responsible for the movement of substance mentioned in answer (b).
(d) Write specific names of the processes which occur in beakers B and C [kinds of processes defined in answer (c)].
(e) Would there be any difference in the weight of the potato cylinder in beaker A after 48 hours? Give reason.
The figure given below is a diagrammatic representation of a part of the cross-section of the root in the root hair zone. Study the same and then answer the questions that follow:
(a) The parts labelled as 1, 2, 3 and 4 are :
- Root hair, Xylem vessel, Soil particles, Cortex respectively.
- Xylem vessel, Soil particles, Root hair, Cortex respectively.
- Root hair, Xylem vessel, Cortex, Soil particles respectively.
- Cortex, Soil particles, Xylem vessel, Root hair respectively.
(b) The process that enables the passage of water from soil into the root hair is :
- Diffusion
- Active transport
- Osmosis
- Passive absorption
(c) The kind of force which exists between a liquid and any surface is called as :
- Cohesive force
- Adhesive force
- Capillarity
- Suction force
(d) The kind of force between the same kind of liquid molecules is :
- Capillary force
- Transpirational pull
- Adhesive force
- Cohesive force
(e) Sometimes exudation of water occurs from the margin of the leaves in early morning or night. It is termed as :
- Transpiration
- Bleeding
- Guttation
- Osmosis
Study the experimental setup in the figure and then answer the questions that follow.
(a) What phenomenon is being studied by this setup?
(b) Explain the phenomenon mentioned in (a) above.
(c) What is meant by 'semipermeable membrane'?
(d) What will you observe in the setup after about half an hour? Give a reason for your answer.
Given below is the figure of a plant cell showing different kinds of pressure acting upon it. Study the figure and answer the questions that follow:
(a) In the figure, 1, 2 and 3 represent :
- Cytoplasm, Nucleus, Vacuole respectively
- Vacuole, Cytoplasm, Cell wall respectively.
- Cytoplasm, Cell membrane and vacuole respectively.
- Cytoplasm, Cell wall and Vacuole respectively.
(b) B in the figure represents :
- Osmotic pressure
- Turgor pressure
- Wall pressure
- Diffusion pressure
(c) A in the figure represents :
- Imbibition pressure
- Wall pressure
- Turgor pressure
- Osmotic pressure
(d) C in the figure represents :
- Turgor pressure
- Osmotic pressure
- Wall pressure
- Imbibition pressure
(e) Draw a neat and labelled diagram of a plasmolysed plant cell.