AGF SciencePot: Cells

Animals and plants are made of cells. Cells form the basic "building blocks" for living things. Some cells have specialised functions.
Tissues are made from cells of a similar type. Organs are made from tissues, and systems are made from several organs working together.

Cells are very small. They are the basic building blocks of all animals and plants. These photographs show cells seen through a microscope.

Cheek cells

These are cheek cells, seen through a microscope:

Onion cells

These are onion cells, seen through a microscope:

Animal cells usually have an irregular shape, and plant cells usually have a regular shape
Cells are made up of different parts. It is easier to explain what these parts are by using diagrams like the ones below.

Animal and plant cells both have a cell membrane, cytoplasm, and a nucleus. Plant cells also have chloroplasts, a vacuole and a cell wall.

Animal cells and plant cells both contain:

cell membrane, cytoplasm, nucleus

Plant cells also contain these parts, not found in animal cells:

chloroplasts, vacuole, cell wall

The table summarises the functions of these parts.

Part	Function	Found in
Cell membrane	Controls what substances can get into and out of the cell.	Plant and animal cells
Cytoplasm	Jelly-like substance, where chemical reactions happen. In plant cells there's a thin lining, whereas in animal cells most of the cell is cytoplasm.	Plant and animal cells
Nucleus	Controls what happens inside the cell. Carries genetic information. In exams don't call the nucleus the 'brain' of the cell. That is not a good description and will not get you marks.	Plant and animal cells
Chloroplast	Where photosynthesis happens – chloroplasts contain a green substance called chlorophyll.	Plant cells only
Vacuole	Contains a liquid called cell sap, which keeps the cell firm.	Plant cells only
Cell wall	Made of a tough substance called cellulose, which supports the cell.	Plant cells only

Humans are multi-cellular animals. That means we are made of lots of cells, not just one cell. The cells in many multi-cellular animals and plants are specialised, so that they can share out the processes of life. They work together like a team to support the different processes in an organism.

Specialised cells

You should be able to work out special features of a cell from a drawing, if you are told what the cell can do. The tables below show examples of some specialised animal and plant cells, with their functions and special features.

Type of animal cell	Function	Special features
Red blood cells	To carry oxygen	Large surface area, for oxygen to pass through Contains haemoglobin, which joins with oxygen
Nerve cells	To carry nerve impulses to different parts of the body	Long Connections at each end Can carry electrical signals
Female reproductive cell (egg cell)	To join with male cell, and then to provide food for the new cell that's been formed	Large Contains lots of cytoplasm
Male reproductive cell (sperm cell)	To reach female cell, and join with it	Long tail for swimming Head for getting into the female cell

Type of plant cell	Function	Special features
Root hair cell	To absorb water and minerals	Large surface area
Leaf cell	To absorb sunlight for photosynthesis	Large surface area Lots of chloroplasts

Tissues

Animal cells and plant cells can form tissues, like muscle tissue. A living tissue is made from a group of cells with a similar structure and function, which all work together to do a particular job. Here are some examples of tissues: