Functions of Life
- Unicellular (single-celled) and multicellular (many cells) organisms must carry out the following functions to stay alive:
- Metabolism - all the enzyme-catalysed reactions occurring in a cell, including cell respiration
- Reproduction - the production of offspring. It may be sexual or asexual
- Homeostasis - the ability to maintain and regulate internal conditions within tolerable limits, including temperature
- Growth - the permanent increase in size
- Response - (or sensitivity), the ability to respond to external or internal changes (stimuli) in their environment. Thus improving their chance of survival
- Excretion - the disposal of metabolic waste products, including carbon dioxide from respiration
- Nutrition - the acquisition of energy and nutrients for growth and development, either by, absorbing organic matter or by synthesising organic molecules (e.g. photosynthesis)
- Unicellular organisms have adapted unique ways to carry out these functions compared to multicellular organisms
- Mitochondria are present to provide energy through respiration
- The cell membrane controls movement of materials in and out of the cell to maintain homeostasis
- Ribosomes are present to produce proteins for growth and repair, in addition enzymes for vital cell functions
- Vacuoles are used for digestion purposes and also to store waste substance
- Cilia or flagella are used for movement of the organism in response to changes in the environment