Bioenergetics is the study of energy transformation in a biological system.
Energy may be defined as the capacity to do work. All living organisms are regarded as working machines which require a continuous supply of energy to keep working and to stay alive.
Living organisms are not able to create energy because according to the law of conservation of energy ( Energy can neither be created nor destroyed but can only be changed from one form to another.
It may occur in various forms such as light, Chemical, heat, electrical, mechanical and sound energy.
Living organisms are able to use chemical form of energy.
Some common examples of use of energy in living organisms are.
1 Synthesis of substances for growth and repair.
2 Active transport of materials
3 Phagocytosis, Pinocytosis and Exocytosis etc
4 Electrical transmission of nerve impulses
Mechanical contraction of muscles and beating of cilia and flagella
5 Heat energy released from respiration used to maintain a constant body temperature in mammals and birds.
Despite energy exists in different forms only two are suitable as energy sources for living organisms, namely light energy and chemical energy, But no organism can make use direct energy of sunlight as a source of energy for metabolism. All living organisms use chemical energy in food molecules such as carbohydrates, proteins and lipids etc.
Photosynthesis and respiration are two main processes involving energy transformation in living organisms. The stored chemical energy in organic compounds is transformed into mechanical energy and heat energy during respiration, this energy is then available to the cell for performing functions.
Photosynthesis act as energy storing while respiration as an energy releasing process.
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