Biology 2016 JAMB Past Questions - Question 14: Fibrinogen and prothrombin play important roles in the

Correct Answer

B

Explanation

Clotting of blood is carried out the platelets orthrombocytes which are cytoplasmic bodies produced by the red& bone marrow of long bones of mammals. When platelets are exposed to air, they release substance/enzyme called thrombokinase. This enzyme in the presence of calciumions and vitamin K converts soluble plasma protein called prothrombin into an enzyme called thrombin. The thrombincbnverts another soluble blood plasma protein called fibrinogen into aninsoluble form called fibnn which cluster at the site of the injury to form adense mesh that traps red biood cells to form a clot that prevents further lossof blood. Options A, C and D are functions of the liver. The liver deaminates or breaks down excess amino acids in the body into urea and glycogen, it detoxicates or converts harmful substances such as toxins or poisons produced by bacteria in our body, additives in the food we ear, drugs, etc into harmless substances for the kidney to excrete them. St also stores certain vitamins eg vitamin B12.