When blood clots, an enzyme is activated to change a protein from one form into another. Describe the process of blood-clotting.

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Process of blood-clotting

The mechanism to prevent excessive loss of blood from the body is called blood clotting.

Steps in blood clotting:At the site of cut, damaged cells and platelets release thromboplastin.This thromboplastin with the help of calcium ions,converts prothrombin into thrombin.In the presence of calcium ions,thrombin reacts with soluble fibrinogen and converts it into insoluble fibrin.Fibrin is a solid substance which forms threads and a meshwork at the site of cut.Blood cells trapped in the network of fibrin.The blood shrinks and squeezes out the rest of plasma in the form of clear liquid.The solid mass which is left behind is called clot.

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B.) nitrogen fixationnitrogen fixation is the process of nitrogen molecules seeping into the soil and inside plant roots and bacteria. it gives more "life" to plants