Chemistry 2 Marks Questions

Due to the physical changes like change in temperature, pressure, or chemical change like change in pH, hydrogen bonds are disturbed. Because of this protein globules unfold and helix gets uncoiled and protein loses its biological activity. This is called denaturation of protein. Denaturation of protein is an irreversible process.
Example : The coagulation of egg white on boiling.

(i) Glucose does not react with iodine solution whereas starch gives blue colour with iodine solution.
(ii) Glucose does not undergo hydrolysis whereas hydrolysis of starch gives glucose.
(iii) Glucose gives red precipitate with Fehling's solution but starch does not give this test.

Aldose whose configuration of carbon atom C 2 differs are called epimers of each other and the process of conversion of one epimer into another epimer is called epimerization. Example: Glucose and mannose. In glucose the - OH group on C 2 is on the right hand side while in mannose it is on the left side.

Carbohydrates are classified as follows:

Reducing sugars have reducing properties, hence they reduce Fehling's solution and Tollens' reagent, like- all monosaccharides, maltose and lactose. Non-reducing sugars do not have reducing properties, hence they do not reduce Fehling's solution and Tollens' reagent. Example : Sucrose.

Nucleic acids are long chain polymers of nucleotides, which are made up of a base, a pentose sugar and a phosphate. They are the biomolecules, which combined with proteins to form chromosomes. Nucleic acids are responsible for the transmission of inherent characters from one generation to the next.
Functions of nucleic acid : There are two important functions of nucleic acid :
(1) Self-replication,
(2) Control protein synthesis.

Deficiency of vitamin A causes diseases like night blindness and xerophthalmia (hardening of cornea of eye) and deficiency of vitamin C causes scurvy (bleeding gums) and dental caries (cavity). Therefore, vitamin A and vitamin C are necessary for us.
Sources of vitamin A : Carrot, spinach, butter, milk, fish liver oil and egg yolk.
Sources of vitamin C : Citrus fruits (lemon, orange, sweet lime), amla, green leafy vegetables, guava, tomato and plum.

(i) In fibrous proteins, the polypeptide chains run parallel and are held together by hydrogen and disulphide bonds to form a fibre like structure, whereas in globular proteins, the polypeptide chains form a coil to give a spherical shape.
(ii) Fibrous proteins are insoluble in water while globular protiens are soluble in water.
(iii) Examples of fibrous proteins are keratin (present in hair, wool, silk) and myosin (present in muscles) and examples of globular proteins are insulin and albumins.

Proteins with specific three dimensional structure and biological activity, found in biological systems are called native (natural) proteins. When native proteins are subjected to physical or chemical changes like change in pH or temperature the arrangement of their hydrogen bonds gets disturbed. Because of this, globules of the protein unfold and helix gets uncoiled and protein loses its biological activity. This is called denaturation of protein. The coagulation of egg white on boiling is an example of denaturation of protein. During denaturation, its primary structures remains unaffected but secondary and tertiary structure are destroyed.
Example : Curding of milk which is caused due to the formation of lactic acid by the bacteria present in milk. Denaturation of protein can be of two types-reversible denaturation and irreversible denaturation.