Most of the processes taking place in cells need energy to make them happen. Examples of energy-consuming processes in living organisms are:
- The contraction of muscle cells – to create movement of the organism, or peristalsis to move food along the alimentary canal, or contraction of the uterus wall during childbirth.
- Building up proteins from amino acids.
- The process of cell division to create more cells,more replace damaged or worn out cells, or to make reproductive cells.
- The process of active transport, involving the movement of molecules across a cell membrane against a concentration gradient.
- Growth of an organism through the formation of new cells or a permanent increase in cell size.
- The conduction of electrical impulses by nerve cells
- Maintaining a constant body temperature in homoiothermic (warm-blooded) animals to ensure that vital chemical reactions continue at a predictable rate and do not slow down or speed up as the surrounding temperature varies.
Respiration is a chemical process that takes place in cells and involves the action of enzymes.
Can sometimes be called cellular respiration, internal respiration or tissue respiration.