BRAINCAKEThe Blood Clotting Cascade
The clot that seals a wound is made in a cascade: a series of reactions in which each step produces an enzyme that catalyses the next step. Because each enzyme molecule converts many substrate molecules, the response is greatly amplified and a clot forms within minutes.
Step 1. Damaged tissue and platelets at the site of injury release an enzyme called thromboplastin.
Step 2. Thromboplastin catalyses the conversion of the soluble plasma protein prothrombin into the enzyme thrombin. This step needs calcium ions (Ca2+) in the plasma as a cofactor. Prothrombin is made in the liver, and the liver needs vitamin K to make it.
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Key terms in this lesson
- cofactor
- A non-protein substance, such as a metal ion, needed by an enzyme for it to function correctly.
More in Circulatory Systems
- Fetal Haemoglobin
- Myoglobin
- Transport of Carbon Dioxide
- Blood Clotting
- Blood Vessels
- Arteries
- Arterioles
- Capillaries
All 33 lessons in Circulatory Systems · All Edexcel AS-level Biology topics