Cell Theory and Cell Structure

Cell theory tells us that all living organisms are made up of at least one cell.

Some organisms exist as single cells, that is are unicellular. This means that each cell has to carry out all the activities necessary for life.

Other organisms can exist a single cells, or as large complexes of single cells in which the tasks necessary to maintain life get shared out.

Animals, and most plants are multicellular, with groups of cells having different tasks being organised into tissues e.g. muscle tissue in animals.
Cells in these organisms have shapes that suit their particular task. This is is known as differentiation.

All cells have some common features, with variations depending on to which of
the five kingdoms of organisms they belong.

You can find out more about the different kinds of cells by

  • visiting the XSIQ pages and looking at the sections on plant and animal cells
  • Continuing on this website
When you have viewed all the information, try this little game.