Living organisms perform numerous chemical reactions every second to maintain life. These chemical reactions are necessary for growth, movement, reproduction, repair, and maintenance of the body. The sum total of all biochemical reactions occurring in a living organism is called metabolism. Therefore, the metabolic basis for living refers to the various metabolic reactions that sustain life.
Metabolism is the total of all chemical reactions taking place inside the cells of living organisms. These reactions help organisms obtain energy, synthesise essential substances, and maintain normal body functions.
Types of Metabolism
Metabolism includes two major types of reactions:
1. Catabolism
Catabolism is the process of breaking down complex molecules into simpler substances with the release of energy. These reactions are degradative and energy-producing. Cellular respiration is one of the most important catabolic processes.
- Releases energy required for life processes
- Produces ATP
- Provides smaller molecules for anabolic reactions
Equation of Catabolism
The equation for aerobic respiration is:
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Examples of Catabolism
- Breakdown of glucose during respiration
- Digestion of proteins into amino acids
- Breakdown of fats into fatty acids and glycerol
2. Anabolism
Anabolism is the process in which simple molecules combine to form complex substances. These reactions require energy and are constructive in nature. Photosynthesis is an important anabolic process.
- Helps in growth and tissue repair
- Stores energy in chemical bonds
- Forms cellular components
Equation of Anabolism
The equation for photosynthesis is:
6CO2 + 6H2O + Light Energy → C6H12O6 + 6O2
Examples of Anabolism
- Protein synthesis from amino acids
- Formation of glycogen from glucose
- Photosynthesis in plants
- DNA and RNA synthesis
ATP: Energy Currency of the Cell
The energy released during metabolic reactions is stored in ATP (Adenosine Triphosphate). ATP provides energy for various cellular activities. ATP is required for muscle contraction, active transport, biosynthesis, and nerve impulse transmission.
The breakdown of ATP releases energy:
ATP + H₂O → ADP + Pi + Energy
Role of Enzymes in Metabolism
Enzymes are biological catalysts that regulate metabolic reactions. They increase the speed of biochemical reactions by lowering activation energy. Without enzymes, metabolic reactions would occur too slowly to support life.
- Protein in nature
- Highly specific
- Effective in small amounts
- Work best at optimum temperature and pH
Importance of Metabolism
- Metabolism is extremely important for the survival and proper functioning of all living organisms because it controls all the chemical reactions taking place inside the body.
- It helps in the production of energy required for performing various life processes such as movement, growth, respiration, circulation, and active transport.
- Through metabolic activities, food substances are broken down to release energy, which is stored in the form of ATP and utilised by cells for carrying out different biological functions.
- Metabolism also plays a major role in the growth and development of organisms by helping in the synthesis of proteins, nucleic acids, lipids, carbohydrates, and other cellular components required for the formation of new cells and tissues.
- It is essential for the repair and replacement of damaged or worn-out tissues, thereby maintaining the normal structure and function of the body.
- In addition, metabolism helps maintain body functions such as digestion, respiration, excretion, temperature regulation, hormonal balance, and nerve coordination.
- Metabolic reactions also help in the removal of toxic substances and waste products formed during cellular activities. Furthermore, metabolism is necessary for reproduction, adaptation, defence mechanisms, and the overall survival of organisms.