Std 12th Biology Board Practical Expt 1
HSC Std 12th Subject Biology Maharashtra State Board Syllabus
Practical Experiment No 01Study of osmosis by potato osmoscope with
ansewers pdf MCQs
Std 12th Biology State Board Practical with Answer
Experiment No 01
1 . Study of osmosis by potato osmoscope.
Date- / /
Aim : - To study the process of osmosis using potato osmoscope.
Requirements -
A fresh Potato, peeler or scalpel, Petri dishes/ bowls/ trough/ shallow glass
beakers, pins, concentrated sugar solution, coloured water, etc.
Principle -
When twosolutionsof different concentrations arcseparated by scmipcrmeahle membrane,
the floss of solvent is front the region of weaker solution (having low solute concentration ) to the region of stronger solution (having high solute concentration) till the equilibrium is reached so that the osmotic pressures an: balanced.Osmosis is of two types viz. endosmosis and exosmosis.
Procedure:-
1.
Take a fresh potato tuber and peel off the skin with the help of scalpel.
2.
Cut the potato from one side in such a way that it will make a flat base.
3.
Scoop the peeled tuber properly so as to make a hollow block (well) in potato
with thin intact base bottom and care should be taken that it will not rupture
at base.
4.
Now add concentrated sugar solution in that cavity and mark its level by
inserting a pin in the cavity wall.
5.
Place this potato osmoscope in a petri dish/ bowl or glass beaker, tilled with
coloured water.
6. Mark the initial level with pin. After some time mark the level of sugar solution in the potato osmoscope.
Observations
After
few hours the level of sugar solution in the potatoosmoscope rises and the solution
becomes coloured.
Inferences
1.The rise in the sugar solution is due to osmosis
2.The membrane of the living cells of potato tuber
functions as a semipermeable membrane.
3. Water from outside (hypotonic) enters the cavity
filled with concentrated sugar solution (hypretonic) thus, demonstrating
osmosis.
Questions
Que 1.
Potato is used to prepare an osmoscope-justify.
Answer
- Peeled potato represents a living system to demonstrate the process of
osmosis.The cell membranes of potato act as the semipermeable membranes and
allowthe passage of water from hypotonic solution to hyperonic solution.
Que
2. Define permeability.
Answer - Permeability is defined as the property of membranes to allow passive diffusion of molecules.
Que
3. Define osmotic pressure.
Answer - Osmotic pressure is equivalent to the pressure which must be exerted upon the solution to prevent the flow of solvent across a semi-permeable membrane.
Que
4. Do you find any role of osmosis in water purification?
Ans - In water purification, reverse osmosis is used. It is the reverse movement of water through a semi permeable membrane from a more concentrated solution to a more dilute solution by applying external pressure on the more concentrated solution. It is used for removing salts from saline water.
5.
Osmosis plays important role in stomatal movement. Explain.
Ans
- Stomatal movement depends on the turgidity of guard cells. Guard cells become
turgid due to endosmosis and the stoma gets open. Guard cells become flaccid
due to exosmosis and the stoma closes.
Multiple Choice Questions MCQs
I In living
cells, an osmosis specifically refers to the movement
a. diffusion
of solvent
b. diffusion of
solute
c. diffusion
of water
d. diffusion of
solute and solvent both
Ans - c. diffusion of water
2 The direction and rate of osmosis is controlled by
a. nature of property of
membrane
b. nature of solvent
c. pressure gradient and concentration gradient
d cell structure
and composition of cytoplasm
Ans - c. pressure gradient and concentration gradient
3. The structure that contributes to the solute potential of a cell is
a. vacuolar sap
b. cell sap
c. water
d. solute particles
Ans - d. solute particles
4. Osmotic
potential refers to
a movement of water molecules from hypotonic solution
to hypertonic
solution
b movement of water molecules from hypertonic solution
to hypotonic
solution
c. pressure potential
d. movement
of water molecules from hypotonic to isotonic solution
Ans - a movement of water molecules from hypotonic solution
to hypertonic
solution
5. Which of the following
is not semiperineable?
a. Parchment
paper
b . Ligg membrane
c. Bladder
membrane
d . C'ell wall
Ans - c.
Bladder membrane
6. Which acid is used to extract egg membrane? .
a. Acetic acid
b. Dilute HCL
c. Concentrated HCL
d. Dilute H2SO4
Ans - a. Acetic acid
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