All living organisms are composed of cells. The structure of a cell relates directly to the function of that cell. In order for a dissolved substance to enter or leave a cell it needs to cross the cell membrane.
By the end of this section you should understand:
- how the structure of a cell relates to it function
Cells and cell structure
Nearly all animal and plant cells contain the following parts:
Nucleus – controls the activities that occur in the cell.
Cytoplasm – the substance in which most chemical reactions take place.
Cell Membrane – the barrier which holds the cell parts together and controls what enters and leaves the cell.
Mitochondria – where the majority of energy is produced through respiration.
Ribosomes – where protein synthesis takes place.
Plant and algal cells sometimes also contain a few of other parts:
Cell Wall – strengthens the cell
Chloroplast – absorbs light energy and produces food by photosynthesis
Vacuoles – are filled with cell sap to keep the cell turgid (or rigid)
Not all cells follow this structure, however. A bacterium is a single-celled organism. It consists of cell wall which contains a membrane and cytoplasm. It does contain genetic material but not in the form of a nucleus.
Yeast is also a single-celled organism. This also consists of cytoplasm and a membrane surrounded by a cell wall but they do contain a nucleus.