All living things are made up of tiny cells.

You can think of cells as the building blocks of living things

Every living organism has at least one cell in it.

Some very tiny animals or plants which usually live in water or in the soil have only one cell.
(see micro-organisms)
Most animals and plants have millions of cells.

If you looked at a cell though a microscope this is what you might see:

cell1
A cell from a human cheek (x 1000)
cell2
PLANT CELL (Leaf cell x 400)


What the words mean

Cell membrane: The living outer layer to the cell.

Nucleus: Controls what is happening in the cell.

Cytoplasm: The liquid inside the cell.

Chloroplasts: These are the things that make plant cells look green. Where photosynthesis is carried out and each one is a tiny food factory.

Large vacuole: The area in a plant cell which contains sap. It helps keep the cell rigid.

Cell wall: The outside layer of a plant cell is called the Cell Wall and helps the plant cell keep its shape.


Organisation of cells

TISSUE: A group of similar cells is called tissue.
For example a piece of skin would be called skin tissue
(the cells are like bricks in a wall…. the wall being the skin)

ORGAN: A group of tissues that have a single use is called an organ. Each organ has a particular job to do. For example the heart is an organ.

ORGANISM: An organism is any complete living thing. For example a human is an an organism and so is a fly. Even a germ is an organism.

Most large animals are made up of many ORGANS.

In order of size:  CELLS  ——>   TISSUE  —–>  ORGAN  ——–>  ORGANISM

[Of course some tiny animals, like the amoeba, do not have organs as they are only a single cell to start with]

cells3 Examples of some cells in a humanA: Sperm cell
B: Nerve cell
C: Muscle cells