METABOLISM
Definition : It is defined as biochemical changes occurring in a living system which facilitate energy changes or transfer of biomolecules. Normal physiological events like respiration, digestion and excretion involve transformation of biomolecules one form to another. These changes involve either release or consumption of energy.
Metabolism involves two opposite processes. They are Catabolism and Anabolism.
Importance of metabolism : Energy is required by a living organism for maintaining it's life. Energy is provided by food which consists of carbohydrates, proteins and lipids. The metabolism of these compounds liberates ATP (adenosine triphosphate) which is a high energy compound. ATP provides the energy required for normal metabolic functions.
Bio genetics is a field of biochemistry which is concerned with the transformation and use of energy by living cells.
Almost all biochemical reactions are mediated through enzymes. Deficiency of the concerned enzyme leads to a metabolic error. This results in abnormal metabolism.
Catabolism : It is a degradative or breakdown process. In this process, macro molecules like carbohydrates, proteins and lipids are broken down. These macro molecules are present in food or stored in the body. These macro molecules are degraded by stepwise reactions into smaller and simpler substances. These reactions are always accompanied by the release of free energy.
Anabolism : It is the opposite of catabolism. Anabolism is a constructive or building up process. In this process, food which is absorbed is used for the synthesis of macro molecules like proteins, lipids and nucleic acids. The synthesis of these macro molecules requires energy, which is supplied by ATP generated during catabolism.
Anabolism and catabolism may occur simultaneously in cells. But these reactions are regulated independently. In health, there is a balance between anabolism and catabolism.
This helps in maintaining weight and health.
Abnormal metabolism : Most of the metabolic reactions are catalysed by enzymes. Deficiency of an enzyme leads to disturbance in metabolism. Enzyme deficiency may be due to -
Dietary deficiency
Diseases
Genetic defects
Dietary deficiency : Deficiency of iron in diet leads to decreased hemoglobin synthesis. This inturn leads to iron deficiency anaemia. Deficiency of iodine leads to defective synthesis of thyroid hormone. It results in hypothyroidism.
Diseases : Metabolism is disturbed in certain diseases. In liver disease, there is decreased synthesis of drug metabolising enzymes. So drugs are poorly metabolised. So drugs may produce toxic effects in liver diseases.
Genetic defects : Some enzyme deficiencies occur due to genetic defects. These defects are called as inborn errors of metabolism. For example, diseases like fructosuria and galactosaemia occur due to inborn errors of carbohydrate metabolism.
