Question

a. Hydrogen bonding

b. Unique properties of water. How are these properties of water crucial for life? Why do they occur?

c. How do molecules dissolve in water?

d. What is pH? Why is this important in biology?

Answer 1

a) Hydrogen bonding occurs when hydrogen forms covalent bond with large electronegetive atoms such as oxygen or nitrogen. It is a weak bond. Example: In H₂O, Two hydrogens bond with one oxygen atom by hydrogen bonding.

b) Unique properties of water are: It is a universal sovent and dissolves a wide range of solutes. This makes water a very useful sovent. Water is a good solvent due to its ability to form hydrogen bonds with solute molecules. Water has a high surface tension that makes insects and other organisms to stay on the surface and not sink to thebottom. The high specific heat capacity of water makes it resistant to changes in temperature and helps in regulation of earth's climate. Water has a high boiling point and low freezing point which keeps it in the most desirable state under the earth's climatic conditions.

c) Molecules dissolve in water as they readily form bonds with water molecules. In case of sugar, weak bonds are formed between water molecules and sucrose molecules. Similarly in case of NaCl, Water being a polar sovent, offers a negetive part to bond with positively charged sodium ion and Chlorine ion bonds with the positive part of water.

d) pH is the measure of the acidity and basicity of a solution. A solution with pH 7 is neutral, 0 to 6 is acidic and 8 to 14 is basic. Mathematically, pH is the negetive logarithm of hydrogen concentration in a solution.

Ideal pH is important for the functioning of enzymes. Enzymes are responsible for carrying our vital processes in a living cell and their functionality is pH sensitive. For example, pepsin that helps to digest protein in our stomach can only work in an acidic medium. Various buffer systems are also present in living organisms to maintain ideal pH for the working of the enzymes.

Protein structure is affected by pH due to protonation or deprotonation of amino acids.