Ministry of Higher Education

and Scientific Research

Tishk International University

Faculty of Education

Department of Biology

Lab. 4

4th Grade (2021 –

2022)

Permeability and Imbibition

By: Zanyar Othman

Zanyar.Osman@tiu.edu.iq

Objectives :

• What is the permeability ?

• The factors which affects permeability.

• What is the imbibition in the plants?

• Factors affecting imbibition.

Permeability

• Capable of being permeated or passed through, used especially of substances where fluids can penetrate or pass through. Supplement. For example, wood is permeable to oil.

Permeability

• The cell membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively-permeable to ions and organic molecules and controls the movement of substances in and out of cells.

• It consists of the phospholipid bilayer with embedded proteins.

Factors Affecting the Rate of Permeability in a Cell Membrane:

1. Molecular size and weight of the solute as the permeability mostly decreases

with increasing size and weight.

2. Lipid solubility’s permeability usually increases with increasing fat or oil

solubility.

3. The degree of ionization as permeability mostly decreases with increased

ionization.

When you heat something you give it energy. Molecules start to spin and vibrate faster. The water will expand too. This will have a disruptive effect on any membrane in its way. Lipids become more fluid as temperature goes up ,so the membranes become more fragile (weak). Proteins formed of coiled and folded strings of amino-acids, held together by hydrogen bonds and disulphide bridges. If you heat them too much, they will desaturated and break apart (vibrations again). When this happens to the proteins spanning a lipid membrane, they will form holes that will destroy the delicate structure.

The freezing degrees of temperatures leads to frosting of water molecules inside the cell and in the intercellular spaces between the cells, which lead to rupture the plasma membrane, thus the movement of molecules will be un-controlled.

4. The effect of temperature:

6. The effect of pH:

If you change the cell’s pH, this can make the proteins to change their shape, as their shape changes this will create holes in the membrane.

7. The effect of poisonous and toxic materials:

These materials act to dissolve some of the cytoplasm components like lipids, also they act to decreases the tension or cohesive force between the cytoplasm and the solution which put in, this affect the structure of the cell membrane and lost its selectively-permeable character.

Practical part:The effect of temperature, pH, salt solutions, and poisonous and toxic substances on the permeability of red beet protoplasmic membrane.

The red pigment contained in beetroots is called beta lain (anthocyanin) this is what gives the beetroot its dark color. Release the dermal layer of the red beets and cut it to small size cubs with thickness 0.2cm approximately.Rinse the cubs very well with tap water, to eliminate the pigment which gets out during cutting.Weight each 2g of the red beet cubs for nine groups.put each the weighted cubs in a test tube, and add 5ml for each tube as the following:Test tube (1): distilled water, and put it at Lab. Temperature.Test tube (2): cold water put it in refrigerator till freezing. Test tube (3): boiled water put it in a beaker containing boiled water.Test tube (4): HCl at concentration (0.1N, pH=1).Test tube (5): NaOH at concentration (0.1N, pH=13)Test tube (6): NaCl at concentration 5%.Test tube (7): CaCl2 at concentration 5%.Test tube (8): NaCl 5% + CaCl2 5%.Test tube (9): Ether or Chloroform.

Imbibition

• The phenomenon of adsorption of water or any other liquid by hydrophilic colloidal materials accompanied with their swelling

• During imbibition, water molecules get tightly attached (adsorbed) on the surface of colloidal particles and become immobilized. They lost most of their kinetic energy in the form of heat. It is called heat of hydration, thus the soaked seeds are warm.

Factors affecting imbibition

I. Increase in temperature brings about an increase in imbibition.

II.The rate of imbibition decreases with increasing in the concentration of solutes in the medium.

III. Imbibition is also affected by acidity and alkalinity.

❖Imbibition is the initial step in the absorption

of water by root hairs.

❖Seed germination.

❖Young un-vacuolated meristematic cells of stem tips get

their water requirements due to imbibition of water

from lower mature cells.

❖The water moves into ovules which are ripening into

seeds by the process of imbibition.

Significance of imbibition in plants

1. The imbibition needs a surface for imbibing liquids, while it’s not in need in diffusion.

2. In imbibition only the solvent transported, but indiffusion the solute and solvent are transported.

Differences between diffusion and imbibition:

Similarities between osmosis and imbibition:

1. In osmosis a semi permeable membrane must be present, while an adsorbent

surface necessary for imbibition.

2. In both of them the solvent transported.

3. The osmotic pressure resembles to imbibition pressure.

Exp. (1): the change of weight and volume after

imbibition's:

• Weight (20) dry seeds of wheat or bean.

• Soak the seeds 1n a beaker containing distilled

water, and mark the volume of the water after

putting the seeds.

• Left it to the end of the lesson, compares the

volume and weight before and after soaking, and

discusses the results.

https://www.youtube.com/watch?v=tPMjVVGLEZM