Roles of Water in Biological Systems:

Cellular Hydration:

Water comprises approximately 75% of most cells, maintaining their structural integrity. Cells require adequate water content to function optimally, and a significant decrease in water levels can lead to cellular damage or death.

Solvent Properties:

Water serves as an excellent solvent, facilitating the movement of various substances within cells. Many essential cellular components and molecules are transported in watery solutions.

Participation in Chemical Reactions:

Water molecules actively participate in vital chemical reactions. For instance, in green plants, water combines with carbon dioxide during photosynthesis to produce glucose. In animals, water aids in the breakdown and dissolution of food molecules during digestion.

Blood Plasma Composition:

Blood consists of cells suspended in plasma, which is primarily composed of water (approximately 92%). Plasma acts as a medium for transporting dissolved substances such as carbon dioxide, urea, digested food, and hormones. Blood cells are transported throughout the body within the plasma.

Transport in Plants:

Water serves as a medium for transporting materials within plants. Xylem vessels transport water and dissolved mineral ions from the roots to the leaves, while phloem vessels transport dissolved sugars and amino acids from the leaves to other parts of the plant.

Excretory Function in Animals:

Water plays a crucial role in the excretory process in animals. It acts as a solvent for excretory materials, including nitrogenous molecules like urea, mineral ions, used hormones, and drugs. By diluting these substances, water helps reduce their toxicity, making them less harmful to the organism.

Diffusion of Water:

When a dilute solution and a concentrated solution are separated by a partially permeable membrane, water molecules undergo a process known as osmosis.

Osmosis Process:

Osmosis is the movement of water molecules across a partially permeable membrane from a region of lower solute concentration (dilute solution) to a region of higher solute concentration (concentrated solution).

The partially permeable membrane allows water to pass through more readily than dissolved substances, resulting in the selective movement of water molecules.

Concentration is the amount of substance present in a particular space. For example, we have 10g of salt present in 200cm3  so the concentration will be regarded as Concentration = Mass/ Grams, concentration will be

Concentration is regarded as the ratio of solute to solvent present in a solution. 

Concentration Gradient:

The dilute solution effectively contains more water molecules than the concentrated solution, creating a concentration gradient that encourages the passage of water from the dilute solution to the concentrated solution.

Water Potential is regarded as the ability to lose water. If you are a dilute solution, your ability to lose water is higher and hence you will lose more water.

Turgor Pressure is the pressure due to water in the cell. It can be regarded as hydrostatic pressure.