Biology Kenya
Cell Physiology
Cell Physiology
Cell Physiology
Meaning of cell physiology
Structure and properties of cell membrane (Theories of membrane structure not required)
Physiological processes - diffusion, osmosis and active transport
Life processes in organisms take place at the cell level. Therefore, it is necessary for substances to move in and out of the cells. There are two ways through which substances can move across the membrane. Materials in living organisms move by diffusion, osmosis and mass flow.DiffusionThis is the movement of materials from a region of higher concentration to a region of lower concentration until equilibrium of two sides is maintained. Diffusion can also be defined as the movement of ions or molecules from the region of higher concentration to the region of lower concentration, without involving any permeable membrane. A difference in concentration of a substance between two regions is known as concentration gradient.Diagram showing diffusion
Role of diffusion, osmosis and active transport in lving organisms
Materials are transported in the body system of living things from the area where they are abundant to areas where they are less abundant, and this process or mechanism of transportation in these animals is termed as diffusion. Diffusion occurs in exchange of gases like oxygen or carbon dioxide during respiration in animals and plants. Also, diffusion takes place during distribution of nutrients and digested foods in living organisms.
- Through the process of osmosis, nutrients get transported to cells and waste materials get moved out of them.
- The pressure within and outside each cell is maintained by osmosis as this process ensures a balance of fluid volume on both sides of the cell wall. If fluid volume within a cell is more than the fluid volume outside it, such pressure could lead the cell to become turgid and explode. On the contrary, if fluid volume outside the cell is more than the fluid volume within, such pressure could lead the cell to cave in. Both cases would be detrimental to normal and healthy cellular function.
- It is via osmosis only that roots of plants are able to absorb moisture from the soil and transport it upwards, towards the leaves to carry out photosynthesis. Plants wouldn't exist without osmosis; and without plants, no other life could exist as they are a vital link of the entire food chain of the planet.
- Without osmosis, it would be impossible for our bodies to separate and expel toxic wastes and keep the bloodstream free from impurities. The process of blood purification is carried out by the kidneys which isolate the impurities in the form of urine.
- Therefore, the role of osmosis is to fold: it helps maintain a stable internal environment in a living organism by keeping the pressure of intercellular and intracellular fluids balanced. It also allows the absorption of nutrients and expulsion of waste from various bodily organs on the cellular level. These are two of the most essential functions that a living organism cannot do without.
Water relations in plant and animal cells: turgor, plasmolysis, wilting and haemolysis
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