Energy:
The capacity to do any work is energy. Energy is required for doing any sort of work and all sort of work physically as well as for all the processes that take place within the body all the time. So, energy is basically needed for:
1. All the voluntary and involuntary work – voluntary includes all the physical work that we do and involuntary work includes all the various processes of our body like respiration, circulation, digestion, excretion, etc.
2. Maintaining the body temperature.
3. The synthesis and renewal of new tissues.
Sources of Energy:
The source of energy for human beings is through the food that we eat. However the main source of energy is sunlight. We are completely dependent on plants for the source of energy, either directly or indirectly through the action of chlorophyll with sunlight by the process is known as photosynthesis.
Forms of Energy:
Potential energy is continuously available in the body from the small amounts of glycogen in muscles and liver, the fat deposits and the cellular mass itself. The potential energy is transformed to other forms for various functions of the body, for example:
1. Mechanical Energy for muscle construction
2. Osmotic Energy to maintain the transport of fluids and nutrients.
3. Electrical Energy for the transmission of nerve impulses.
4. Chemical Energy for the synthesis of new compounds
5. Thermal Energy for heat regulation
The formation of ATP occurs in the metabolic pathways. Initially these nutrients are oxidized interdependently to the common denominators, namely pyruvic acid, accetyle coenzyme A and alpha Ketoglutaric acid. These common denominators enter the Tri-carboxylic acid (TCA), which is the common pathway for the oxidation of glucose, fatty acids and amino acids. About 90% of the energy liberated from food occurs by the pathway. Oxidative phosphorylation is the mechanism whereby the hydrogen’s yielded by the TCA cycle are passed along the respiratory chain and energy is trapped as ATP below figure: