The average, non-specialised body cell can be broken down into certain common biochemical constituent molecules:
- DNA: the genetic cell template
- water:
- the largest component: occupies more than two thirds of cell
- provides a fluid environment for chemical reaction
- gives cell volume and support
- a substrate for vital metabolic reactions
- electrolytes; much different to the concentrations in the extracellular fluid:
- potassium is key intracellular ion
- sodium at relatively low concentration
- minute concentrations of magnesium, bicarbonate, phosphate, chloride and sulphate
- calcium concentration is normally relatively low in relation to extracellular fluid: this permits its use as an intracellular signalling molecule; signals transducted across the cell membrane cause a rapid rise in calcium levels
- calcium also acts as a co-factor for a number of specialised proteins
- trace ions e.g. manganese, zinc, iron, copper and selenium all combine with proteins, usually enzymes, to act as co-factors
proteins:
þþ structural proteins e.g. cytoskeletal tubulin
- enzymes:
- present in cytoplasm and membrane
- vital role in all cell metabolism, the transduction of signals to and from their environment, and special functions dependent on the cell, e.g. striated muscle contractility through actin and myosin
- carbohydrate: many roles including alteration of proteins and glycogen energy source
- lipids: acts as vital membrane constituent and energy store