There is no such thing as the convenient term ‘a typical cell’ would suggest BUT all living cells have many chemical reactions and physical features in common.
Chemical reactions taking place within and around living cells follow all the established laws of chemistry and physics.
The commonality of these features in animal and plant cells the world over is a very important concept. It is thought that most of the features have been conserved over millions of years; many from the ‘ancestral cell’ 3 billion years ago.
About 99% of the mass of living cells is composed of the elements carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur. The remaining 1% includes small amounts of the elements calcium iron, zinc, sodium, potassium, chlorine, selenium and iodine, and very small amounts of molybdenum, manganese fluorine and chromium.
Hydrogen and oxygen as water accounts for approximately 70% of the mass of a cell.
In addition to water the elements present are mainly built into four main chemical groups: carbohydrates, proteins, fats and nucleotides (nucleotides are important molecules used in the construction of RNA, DNA and energy transfer molecules such as ATP).
These four main groups can form other biologically important chemical groups.
- Carbohydrates can link with proteins to form glycoproteins (glyco from Greek, glykis, meaning sweet). – Glycoproteins are found extensively in animals and plants where they help cells adhere to one another through a material called extra cellular matrix. In animals glycoproteins are closely associated with the very important collagen fibres.
- Carbohydrates can link with fats or lipids to form glycolipids – glycolipids are closely associated with membranes of the brain and nerve cells
- Fats or lipids can link with protein to form lipoprotein– these molecules are used in the construction of many biological membranes and in the transport of dietary fat.
- Nucleotides can link with proteins to form nucleoproteins. – Viruses, a ribosome (a cell organelle) and chromatin are largely nucleoprotein. Chromatin is DNA linked to a protein called histone.
- All livings cells the world over have many chemical and physical features in common. Most of these features have been conserved over millions of years.
- Chemical reactions within cells follow all the established laws of chemistry and physics.
- Most of the chemicals in cells are carbohydrates, proteins, fats or nucleotides or combinations or derivatives of them.