Water in cells and its importance of maintaining narrow range for optimal function
Water in cells should be maintained in narrow range of concentration for optimal function.
What happens if water concentration of a cell increases beyond the range?
If we put a cell in a hypotonic solution… (Solution with less salt concentration)
Osmosis is the net movement of water molecules from a region of high concentration to a region of their low concentration through a selectively permeable membrane.
Therefore water molecules move from external watery environment to the cell. This is known as endosmosis.
If a plant cell has low water potential than the narrow range, water molecules move towards the cell until the concentration of cell reaches the narrow range. Therefore the cell will absorb water until it reaches the maximum volume. Rigid cell wall controls the volume of cell. This state is known as turgid.
If animal cell has lower water potential than its limit the cell will absorb water from external environment. Animal cells do not have cell wall. Therefore there is no limitation for absorption of water. Cell will burst when their volume exceed than maximum level. This can be seen if we place a red blood cell (erythrocyte) in distilled water on a microscopic slide and observe under the microscope. Red blood cell soon begins to inflate and burst like an inflated balloon.
What happens if water concentration in cell decrease below its range?
If we put a cell in a hypertonic solution… (Solution with high salt concentration)
The cell start to shrink due to water in cell moves out side the cell. This is known as exosmosis.
In Plant cell the cytoplasm is attached with cell wall due to shrinkage the cytoplasm will shrink and detached from the cell. This shrinkage is known as plasmolysis. Eventually cell will die due to loss of water.
In animal cell will start to shrink without any limitations causing the cell to die due to loss of water (dehydration).
Importance in plants
Cells can be expanding only up to 10% of original size. If the cell expands beyond the limit the functional abilities of the cell lose due to permanent changes in the cell wall & plasma membrane. Cell need certain amount of turgidity to main its shape. If water concentration decrease beyond the limit the cell looses its shape and becomes flaccid. Therefore the concentration in cell should be with in the limit. Root pressure is essential for absorption and conduction of water. If water concentration decrease below the normal range plant cannot support transport. Dehydration occurs resulting in death of plant. Therefore water concentration should be maintained to have a constat root pressure.
Plants are important in food chain because they are the producers. Photosynthesis is the process by which plant produce simple sugars. The dark reaction is part of photosynthesis. It occurs in aqueous medium, which is known as stroma found in chloroplast. Therefore water concentration should be maintained in with in a narrow range to maintain steady internal environment of the chloroplast.
Importance in animals
The concentration of water is important for aquatic animals such as fish. There are fresh water fish, hyper saline water fish, and seawater fish. Their internal concentration ion concentration differs according to their environment. If fish environment change there internal environment change dramatically and end up in death.
Urea and nitrogenous wastes continuously added into internal environment. This will change the internal environmental composition. Ammonia and other nitrogenous wastes can be toxic if they exceed a certain level. Therefore periodically nitrogenous waste products have to be regulated. Water concentration should be maintained to prevent ammonia and other nitrogenous compounds are toxic.
Importance in both Animals and plants
Active transport is transport method by which substances move across a concentration gradient, an area of low concentration to high concentration with the expenditure of energy. Active transport occurs by the translocation and hydrolysis of ATP. Sodium ions and potassium ions are essential for translocation and hydrolysis of ATP. Ion concentration will change if the cellular water concentration change. Therefore cellular water concentration should be controlled to maintain constant ion concentration.
Active transport in small intestine
Mineral Abortion in root hair
Respiration takes place in mitochondria. Respiration is essential for production of energy ATP molecule from Glucose. Mitochondrion internal environment should be maintained to have normal respiration.
Components of cell membrane are bi lipid layer of phospholipids, protein molecules and carbohydrates