Defining Life
Life is the characteristic that distinguishes objects that are organisms (have signalling and self-sustaining processes) from those that are not.
All life depends on a series of complex chemical exchanges.
Fundamental Characteristics (Exhibit all/most)
- Reproduction
- Creating offspring
- Growth
- Anabolism > Catabolism (i.e. more molecules are constructed than destructed)
- Adaptation
- Changing over time in response to the environment
- Metabolism
- Converting chemicals and energy into cellular components (i.e. they have anabolism and also catabolism - they decompose things).
- Response to Stimuli
- Any kind of reaction brought on by an external change - sunlight or a chemical change in the environment. The reaction can be movement, contraction, releasing a toxin, etc.
- Organisation
- Being structurally composed of cell(s).
- Homeostasis
- Regulating the internal environment to maintain a constant state. (E.g sweating for temperature regulation).
Possess Chemicals of Life
- Usually due to having cells (hence explained over there), but viruses have these without them)
- Carbohydrates
- Store and transport energy and structural components
- Composed of Carbon chains with water molecules
- Monosaccharides are the basic unit, but they can combine
- Proteins
- Polymers formed from linked amino acids
- Joined with peptide bonds
- Lipids
- Different kinds of fats. E.g.
- Fat-soluble Vitamins
- Waxes
- Cholesterol
- Monoglycerides
- Hydrophobic
- Energy Storage and Structural composition of the cell membrane
- Different kinds of fats. E.g.
- Nucleic Acids
- Genetic Material
- Storage and transfer of genetic information
- DNA Nucleotides:
- Purines: Adenine, Guanine
- Pyrimidines: Cytose, Thymine
- 3 components to nucleotide:
- pentose sugar
- phosphate grou
- nitrogenous base
- Polymers = links of various nucleotides
page revision: 2, last edited: 17 Mar 2013 00:10