During a laboratory experiment, a student immerses epidermal leaf peel in a hypertonic solution. After some time, the student examined the cells under a microscope and observed that:
- A.the cells swelled.
- B.the cells were plasmolysed.
- C.the cells built up turgor pressure.
- D.the cells size was unaffected.
Correct answer
Explanation
The correct answer is B, the cells were plasmolysed. A hypertonic solution has a higher solute concentration than the cell sap, so water leaves the cells by osmosis and the protoplast shrinks away from the cell wall. This shrinking of the living contents away from the wall is called plasmolysis, and it is easy to see in the coloured cells of a leaf peel such as Rhoeo. The rigid cell wall keeps its shape, so the gap between wall and membrane fills with the outside solution. If the peel is moved to water soon enough, water re-enters and the cells recover, a process called deplasmolysis. Option A is wrong because cells swell only in a hypotonic solution, when water moves in. Option C is wrong because turgor pressure falls, not rises, when a cell loses water. Option D is wrong because size stays the same only in an isotonic solution, where no net water moves. Exam tip: hypertonic = plasmolysis; hypotonic = turgid; isotonic = no change.
Practice Questions
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- A.Ammonium nitrate
- B.Ammonium sulphide
- C.Ammonium phosphate
- D.Ammonium sulphate
Show answer
Ammonium sulphide is an unstable, foul-smelling compound that breaks down to release ammonia and toxic hydrogen sulphide, so it is not used as a fertiliser.
Read the full explanation →The focal length of the objective lens of a telescope is 50 cm. If the magnification of the telescope is 25, then the focal length of the eye-piece is
- A.12.5 cm
- B.5 cm
- C.2 cm
- D.10 cm
Show answer
For an astronomical telescope in normal adjustment the magnifying power equals the focal length of the objective divided by that of the eyepiece, so the eyepiece focal length is 50 ÷ 25 = 2 cm.
Read the full explanation →The major source of vitamins and minerals for vegetarians is
- A.black gram and wheat.
- B.rice and mustard.
- C.vegetables and fruits.
- D.soya bean and milk.
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Vegetables and fruits supply most of the vitamins and minerals in a vegetarian diet, which is why they are called protective foods.
Read the full explanation →Which one of the following compounds is used in black and white photography?
- A.AgF
- B.AgBr
- C.AgCl
- D.Ag2SO4
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Silver bromide is the light-sensitive compound coated on black and white photographic film and paper, because light breaks it down into tiny grains of silver metal.
Read the full explanation →Which one of the following statements about speed and velocity is correct?
- A.Speed and velocity both are vector quantities.
- B.Speed and velocity both are scalar quantities.
- C.Speed is vector quantity and velocity is scalar quantity.
- D.Speed is scalar quantity and velocity is vector quantity.
Show answer
Speed tells only how fast a body moves, while velocity also tells the direction of motion, and a quantity with both magnitude and direction is a vector.
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