Osmotic relations of plant cells - class-XII

Plant cells typically have large central vacuoles, which are essential for maintaining turgor pressure and storage. Therefore, the statement that vacuoles are absent in plant cells is incorrect.

• Water potential is the energy potential of water compared to pure water in a system when both temperature and pressure are same .
•  When the contents of the the cell moves out then then the wall pressure or turgour pressure will decrease .
  

Crenation is defined as the process by which a blood cell shrinks when it is exposed to a hypotonic solution.

Cell wall is the outermost, rigid, protective, non living and supportive layer found in all the plant cells. Due to its rigid nature it prevent the cell from bursting. It is not found in animal cells. An animal cell placed in pure water will swell up and burst, because of endosmosis.

When a grape is placed in a solution of concentrated sugar solution, it will show the process of exosmosis and lose water. When a cell is kept in hypertonic solution, it readily crosses the cell wall and fills the space between the cell wall and cell membrane. This hypertonic solution in direct contact with the cell membrane causes plasmolysis and extracts water from the cytoplasm of the cell.

The cell wall is nonliving and cannot regulate the entry and exit of solute or solvent molecules. When a cell is kept in hypertonic solution, it readily crosses the cell wall and fills the space between the cell wall and cell membrane. This hypertonic solution in direct contact with the cell membrane causes plasmolysis and extracts water from the cytoplasm of the cell.

Because halophytes are the plants of saline habitat.

An osmometer is a device for measuring the osmotic strength of a solution.
Photometer is an instrument for measuring the intensity of light.

Suberin and cutin are complex macromolecules which mainly function as a barrier to movement of water and solutes. Thus if a higher plant cell is covered with cutin and suberin and placed in water then there will not be any change in the size of the cell as cutin and suberin are hard and water repulsive substances. There will not be any exosmosis or endosmosis in such type of cell.

Here O.P. stands for osmotic pressure, D.P.D. stands for diffusion pressure deficit and T.P. stands for turgor pressure. 

A concentrated NaCl solution is hypertonic to the plant cell. Water leaves the cell via osmosis, causing the cytoplasm to shrink away from the cell wall, a process known as plasmolysis.

(A) Endosmosis is the movement of solution from outside of the cell to inside the cell.

• Osmosis occurs only through the semi-permeable membrane. Osmosis is a gradient dependent process, osmosis is different from diffusion as it is characterized by a semi-permeable membrane.
  
• Net direction and rate of osmosis depend on both pressure gradient and concentration gradient.

The hypertonic solution involves the movement of a solute particle from low concentration to high concentration. The water will move from a higher concentration to a lower concentration. The cell will swell up.

Osmotic pressure is generated when solutes are added to water. It depends on the concentration of a solution.

The solute potential is always negative as it reduces osmotic pressure.

Vacuoles are the organelles that store all the extra water and salts that are the basis of creating osmotic pressure in the cell. The vacuole takes up a huge central place in the cell. The solution outside the cell is hypertonic, hypotonic or isotonic with respect to the contents inside the vacuole. Plastids are the centres for photosynthesis, Ribosomes are small granule-like structures that help in protein synthesis whereas mitochondria generate energy for the cell by utilising sugars. 

RBCs placed in distilled water will burst because distilled water is extremely hypotonic to the cytoplasm of the cell. This will involve the intake of enormous amounts of water and the cells will burst.

When a cell is placed in an hypertonic solution water is transported out of the cell and the cell shrinks or shrivels or plasmolysed. On contrary when the cell is placed in hypotonic solution the water flows into the cell causing the cells to swell and finally leading to their lysis. However, when the cells are placed in isotonic solutions there will be continuous flow of water in and out of the cell and the cell is said to be in flaccid condition. Thus, the correct option of C.

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.

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.

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.

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. 

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.

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.

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. 

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.

A Hypertonic solution is a solution, which contains higher solute concentration. If mammalian liver cells are kept in hypertonic solution then exosmosis will occur. Exosmosis is a process in which outward movement of water molecules takes place from inside of lower solute concentration to the outside of higher solute concentration through the cell membrane. Due to exosmosis, mammalian liver cells will shrink. So, the correct answer is option B.

Grapes were put in sugar solution i.e., in hypertonic solution. Due to which exosmosis occurs in which outward movement of the water molecules from the lower solute concentration to higher solute concentration takes place through grapes covering. It results in shrinking of grapes. Therefore, option D is correct.

If amoeba is kept in hypertonic solution then exosmosis occurs in which the water molecules move outward from cell of lower solute concentration to surrounding medium of higher solute concentration through the cell membrane. Due to exosmosis, amoeba will shrink. 

The lower the concentration of the salt solution, the higher will be the water potential of that solution. The higher the water potential, the greater is the tendency for water to enter the cell by osmosis. If there is more water entering by osmosis, then the contractile vacuole will have to fill up and empty more frequently. 

Water passing from a xylem vessel element to xylem vessel element above it due to the transpiration pull exerted by the mesophyll cells. However, the transfer of water from the soil to the root is due to osmosis.

Manometer is a device that is used to measure pressure. Photometer is a device that is used to the intensity of light. Calorimeter is a device that is used to measure the amount of heat involved in a reaction. Osmotic pressure is the pressure that must be applied in order to prevent the passage of solvent due to osmosis. The OP of a cell can be measured by plasmolysis. The OP of a cell is equal to the OP of a solution that results in the incipient plasmolysis in the cell.

(A) Diffusion is the movement of the water molecule from higher concentration to lower concentration.

DPD is the difference between Osmotic pressure and Turgor pressure. 

Colligative properties are the characteristics of solutions which depend on the ratio of the number of solute particles to the number of solvent molecules in a solution. It does not depend on the quality of the chemical species present.

Distilled water is a hypotonic solution contained within the red blood cell membranes that is why distilled water will diffuse into the red blood cells and cause them to burst.

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 osmosis in which the water molecules move from lower solute concentration to higher solute concentration through cell membrane 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 the water molecules will move from hypotonic solution to onion cells. This process is called as osmosis in which the water molecules move from lower solute concentration to higher solute concentration through the cell wall of onion. 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 B.

When the cells are kept in a hypotonic solution, endosmosis occur, i.e., inward movement of water. This results in the swelling up of the cells. The RBCs burst easily because they are animal cells and do not have cell wall. The onion peel possess cell wall which makes it resistant to bursting due to swelling caused by endosmosis. Therefore, option D is correct.

When RBCs are kept in concentrated saline solution then such solution is said to be hypertonic. Hence, exosmosis i.e., water will move from inside to outside of RBC through its cell membrane due to this, RBCs will shrink.

Wall pressure is equal and opposite to the turgor pressure.

Endocytosis is the process in which cells absorb molecules by engulfing them. The cell membrane engulfs food and other materials by endocytosis. The plasma membrane creates a small deformation inward, called as an invagination, in which the substance to be transported is captured. The deformation then pinches off from the membrane on the inside of the cell, creating a vesicle containing the captured substance. Endocytosis is a pathway for internalizing solid particles, small molecules and ions and macromolecules. Endocytosis requires energy and is thus, a form of active transport.

Imbibition is a special type of diffusion when water is absorbed by solids- colloids causing an enormous increase in volume. Examples include the absorption of water by seeds and dry wood.

Following are the correct statements: 

Imbibition is the initial step in the germination of the seeds. When mature seeds are sown in soil they imbibe water and swell. The water is imbibed first by seed coat and then by other tissues of embryo and endosperm. The process of imbibition is important ot initiate the seed germination. the pressure that an imbibant develops when submerged in pure imbibing liquid is called imbibition pressure.

Imbibition pressure generated during germination of seeds and spores is so enormous that it can break asphalt roads and concrete pavements. In older times, the imbibition pressure was used in breaking the rocks and stones. Dry wooden stakes, if driven into a small crack in a rock and then soaked, can develop enough pressure to split the rock.

When the two solutions having different osmotic concentrations are separated by means of a semipermeable membrane, the molecules of solvent or water move from the region of their higher diffusion pressure (or free energy) to the region of their lower diffusion (or free energy). This movement of water or solvent is called osmosis.

Imbibition is the process of absorption of water by hydrophilic solid particles. It is a special type of diffusion as the water moves along its concentration gradient. The classical example includes the absorption of water by seeds. This process plays an important role in the germination of seed, rupturing of the seed coat, and the emergence of seedlings is due to imbibition pressure developed by the seed kernel.

Coffee and tea tastes uniformly sweet due to the diffusion of solvent from the high concentration to the lower concentration. There is no membrane and it is not the case of osmosis and permeability.

A semi-permeable membrane doesn't allow larger molecules. It will allow dissolved molecules and water to pass through according to the concentration gradient and the chemical nature of the substances.