41.

(a) Explain the role of pancreas in digestion of various food materials.

(b) Briefly describe the stages in clotting of blood.

(c) Define: (i) Reparative regeneration (ii) Capacitation (iii) Menarche.

(a) Digestion of carbohydrates : Pancreatic juice contains pancreatic amylase which converts starch, dextrin and glycogen to diglycerides like maltose and isomaltose and limit dextrins.

Digestion of Proteins : It contains three inactive proteases – trypsinogen , chymotrypsinogen and procarboxypeptidase.

1. Trypsinogen — This proenzyme is first activated to an enzyme trypsin by an enzyme enterokinase trypsin breaks more proteins into proteoses and peptones (peptides).

2. Chymotrypsinogen — Chymotrypsinogen is converted to the active form called  chymotrypsin by trypsin. The activated enzyme splits proteins into peptides.

3. Procarboxypeptidases — are converted to active enzymes carboxypeptidases by trypin which produces amino acids and dipeptides.

(i) Digestion of fats : Pancreatic lipase present in pancreatic juice digests triglycerides (fats) and splits it into fatty acid and glycerol.

Digestion of Nucleic acids: Pancreatic juice contains deoxyribonuclease and ribonuclease .
(i) Deoxyribonuclease hydrolyses DNA into deoxyribonucleotides.

(b) Coagulation is brought about by the hydrolysis of soluble fibrinogen of the plasma and its conversion to the insoluble fibrin. The reaction is catalysed by an enzyme, thrombin. Fibrin precipitates as a mesh of fibres. This mesh traps both erythrocytes and leucocytes to form a solid mass, the blood clot. The clot seals the wound to stop bleeding.

Thrombin is present in the blood as a precursor called prothrombin. It is converted into active form, thrombin, in the presence of ions and thromboplastin released into blood from clumped platelets and damaged tissues at the site of the injury.

(c) (i) Reparative regeneration : In this organism has the power only to repair certain damaged cells of the body, eg liver.

(ii) Capacitation : Spermatozoa acquire ability to fertilize ovum only after they have been in female genital tract for sometime. This final step in their maturation is called Capacitation.

(iii) Menarche : Appearance of first menstrual flow in the life of a girl.