Tag: transport across membrane

Questions Related to transport across membrane

When a plasmolysed cell is placed in a hypotonic solution then water will move inside the cell. Which force causes this?

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. DPD

  2. OP

  3. WP

  4. None of these

Show answer
Correct Option: A
Explanation:
The DPD or diffusion pressure deficit represents the water absorbing capacity of a cell. It is given by, DPD = osmotic pressure (OP)- turgor pressure (TP). Since turgor pressure is negative in a plasmolysed cell the DPD will be high (maximum). This will cause water to enter into the cell when it is placed in a hypotonic solution. The entry of water will stop only when the cell is fully turgid. In such condition, the OP and Tp will be equal and hence DPD will be 0. Therefore, DPD determines the ability of the cell to absorb water. So, the correct option is ' DPD'.

Which of the following statements is correct?

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. Bacteria do not survive in salted pickles because they get plasmolyzed in hypertonic medium.

  2. Osmotic potential is numerically equal to the osmotic pressure but is negative in sign.

  3. Kneading of wheat flour is accompanied by release of heat as a result of water being imbibed by the protein in the flour

  4. All of these

Show answer
Correct Option: D
Explanation:

A- Salting is used because most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment, due to the hypertonic nature of salt. Any living cell in such an environment will become dehydrated through osmosis and die or become temporarily inactivated.

B- The modern plant physiologists have substituted the term osmotic pressure (O.P.) by osmotic potential. However, it is to be noted here that osmotic potential is numerically equal to the osmotic pressure but is negative in sign and it (osmotic potential) is denoted by ψ(psi). Thus
O.P = – ψ or ψ = –O.P.

So, the correct option is  'Option D'.

Which of the following statements does not apply to reverse osmosis?

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. It is used for water purification

  2. In this technique, pressure greater than osmotic pressure is applied to the system

  3. It is a passive process

  4. It is an active process

Show answer
Correct Option: C
Explanation:

Osmosis is passive transport where water follows down the gradient across a semi-permeable membrane from a higher concentration to a  lower concentration. Reverse osmosis simply means that the cumulative pressure gradients cause the flow of water molecules to go against the osmotic pressure gradient from a lower concentration to the higher concentration. 
As the process of reverse osmosis requires energy for transporting molecules against the concentration gradient, it is an active process.

The concentration of solute in four cells is $0.4\,M$. They are placed in four separate containers I, II, III and IV, filled with saline water of concentration $0.1\,M$, $0.4\,M$, $2\,M$ and $3\,M$ respectively. In which container will the cell swell?

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. $I$

  2. $II$

  3. $III$

  4. $IV$

Show answer
Correct Option: A
Explanation:

Concentration of container-I with respect to the cell is hypotonic, therefore, endosmosis occurs and water will move from its higher concentration towards its lower concentration(i.e., from container to cell), as a result of which cell in container-I will swell.

The maximum pressure developed in a solution when separated from pure water by a semipermeable membrane is called

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. Turgor pressure

  2. Wall pressure

  3. Osmotic pressure

  4. DPD

Show answer
Correct Option: C
Explanation:

Osmotic pressure refers to the maximum amount of pressure, which gets developed in a solution after separating from a pure solvent with the help of a semipermeable membrane. In other words, osmotic pressure is the maximum pressure required to prevent the flow of pure water into a given solution through osmosis.

A plant cell placed in pure water will

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. expand until the osmotic potential or solute potential reaches that of water

  2. becomes more turgid until the pressure potential of cell reaches its osmotic potential

  3. become more turgid until the osmotic potential reaches that of pure water.

  4. becomes less turgid until the osmotic potential reaches that of pure water.

Show answer
Correct Option: B
Explanation:

Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution, it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting. The plant cell is said to have become "turgid" i.e. swollen and hard. The pressure inside the cell rises until this internal pressure is equal to the pressure outside. This liquid or hydrostatic pressure called the turgor pressure prevents further net intake of water. 

So the correct answer is 'becomes more turgid until the pressure potential of the cell reaches its osmotic potential'.

If a red blood cell (interior concentration of 0.9% salt) was placed into a test tube of 10% salt, what would happen to the red blood cell?

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. It would fill with water and burst

  2. Nothing, the solution is isotonic to the interior of the red blood cell

  3. The red blood cell would shrink as it loses water to the salt solution in the test tube

  4. None of these

Show answer
Correct Option: C
Explanation:

In this case, the concentration of solution outside the blood cell is more and is thus called as hypertonic. It infers that the cell will shrink, as the water inside the cell moves outside making the cell flaccid. This process is called exosmosis. It happens because of the variation in the concentration gradient.

So, the correct answer is option C.

What will happen if a plant and animal cell is put in a hypotonic solution?

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. Cell swells

  2. Cell shrinks

  3. Cell bursts

  4. None of these

Show answer
Correct Option: A
Explanation:

Hypotonic solution is a solution which, contains lesser solute concentration. If animal and plant cells are kept in a hypotonic solution then endosmosis will occur. Endosmosis is a process in which the water molecules move from outside of the cell of lower solute concentration to the inside of the cell of higher solute concentration through the cell membrane or cell wall. Due to endosmosis, both animal and plant cells will swell. So, the correct answer is option A.

What will be observed when a plant or animal cell is put in a hypertonic solution?

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. Cell swells

  2. Cell shrinks

  3. Cell bursts

  4. None of these

Show answer
Correct Option: B
Explanation:

A Hypertonic solution is a solution, which contains higher solute concentration. If animal and plant cells are kept in hypertonic solution then exosmosis will occur. Exosmosis is a process in which the water molecules move from inside of the cell of lower solute concentration to the outside of the cell of higher solute concentration through the cell membrane. Due to exosmosis, both animal and plant cells will shrink. 

So, the correct answer is option B.

If cells of onion peel and RBC are separately kept in hypotonic solution, what among the following will take place? 

bio-chemistry absorption by roots - the processes involved osmotic relations of plant cells transport across membrane imbibition and its importance

  1. Both the cells will swell

  2. RBC will burst easily while cells of onion peel will resist the bursting to some extent

  3. Both A and B

  4. RBC and onion peel cells will behave similarly

Show answer
Correct Option: C
Explanation:

Hypotonic solution is a solution which contains lesser solute concentration. If RBC is kept in hypotonic solution, then the water molecules will move from hypotonic solution to RBC. This process is called as endosmosis in which the water molecules move from lower solute concentration to higher solute concentration through the membrane of RBC. Due to this, the cell membrane of RBC will not be able to tolerate the pressure and it will burst eventually. If onion peel is kept in hypotonic solution, then endosmosis will occur. As onion cell possess cell wall along with the cell membrane the onion cell will take a longer time to burst than RBC, but it will burst eventually.

So, the correct answer is option C.