Revision guides: Cell biology

Cells are microscopic building blocks of unicellular and multicellular living organisms. Animal, plant, fungal and bacterial cells are different in terms of structure but also have many similarities.

All cells are enclosed by a cell membrane, which is selectively permeable. Molecules can move into or out of cells by diffusion and active transport. Cells can gain or lose water by osmosis.

DNA carries the genetic information in the cells of all living organisms. It contains codes for the assembly of amino acids into all the proteins required in the body.

Proteins consist of combinations of amino acids. Body proteins include structural proteins, enzymes, hormones and antibodies. The shape of an enzyme allows it to speed up a biological reaction.

Bacteria exchange DNA using plasmids; viruses invade cells by first inserting their genetic material. Genetic engineering is the transfer of DNA between organisms using biotechnology.

Most cell activity requires chemical energy. Respiration is the cellular process of releasing energy from food and storing it as ATP.