Biology BIOMOLECULES

Water :

(1) It is a best solvent in nature, it forms the fluid matrix of protoplasm. All other constituents of protoplasm are its solutes.

(2) Being an ideal dispersion medium, it causes Brownian movement of colloid particles, resulting into their collision and mutual bombardment. This facilitates reactivity between the various compounds necessary for maintaining protoplasm in live state.

(3) It causes streaming or cyclosis in protoplasm transportation of solutes from one part to the others.

(4) It itself participates in certain types of chemical reactions, particularly in the hydrolytic breakdown of complex
compounds.

(5) Having a high specific heat, it minimises temperature variations and thus protects protoplasm against ill effects of sudden rise or fall of temperature in the environment.

(6) Of total water, 95% water is free water and 5% water occurs as bound water.

(7) Water in human body- 65-70% of total body weight.

(8) Human body ` approx 40` litre :
`55%` (22 litre) - intracellular fluid
` 45%` (18 litre) - extracellular fluid
(9) In animal kingdom - Hardest material : Enamel
(10) In plant kingdom - Hardest material : Sporopollenin

Salts :

(1) Salts in protoplasm occur in ionised form. These ions are responsible for electric conductivity, rendering protoplasm
irritable and response to environmental changes.

(2) These provides linkage or chemical bonds in many chemical reactions. Such type of linkage called "Salt linkage".

(3) Some metallic and other ions such as Mg, Fe, Zn, Mo, Mn etc. act as cofactors in enzymatic activities.

(4) These regulate the osmotic pressure and chemical exchange of protoplasm from its environment.

(5) Some ions also act as co-factor :
`Zn^(+2) ` - Carbonic anhydrase
` Cu^(+2)` - Tyrosinase [CBSE 20041
`Fe^(+2)` - Aconitase, catalase
`Mo` - Nitrogenase
`Mg^(+2)` - Co-factor of many respiratory enzymes like Kinase, Enolase. Dehydrogenase
`Ni `- Urease enzyme

(6) Some other functions of ions :
`Na^(+) , K^(+)` ions- Nerve induction
`Ca^(+2) , Mg^(+2)` ions- Muscle contraction, Reduce more excitability of nerves and muscle.
`Ca^(+2)` ion -Blood clotting, Bone formation
- Most abundant mineral element in animal body

`Na^(+) , K^(+)` ions- Main component of ringer solution.
`K^(+)` ion- Helpful in seismonastic movement, stomatal opening and closing.

Acids and Bases :

These prevent pH variations by forming a buffer system in protoplasm, for e.g. carbonic acid-Bicarbonate
buffer system.