CCEA GCSE Biology

## Animal cells An animal cell is bounded by a **cell membrane**, which controls what enters and leaves. Inside it the **cytoplasm** is the watery jelly where most chemical reactions of the cell take place. The **nucleus**, itself surrounded by a nuclear membrane, contains the chromosomes that carry the cell's genetic information and controls the activities of the cell. **Mitochondria** are the site of aerobic respiration, which releases the energy the cell uses, so cells that do a lot of work, such as muscle cells, have many of them. ## Plant cells A plant cell has all of those structures and three more that an animal cell lacks: - a **cell wall** made of cellulose, which is outside the cell membrane, supports the cell and stops it bursting when water enters; - a large **permanent vacuole** filled with cell sap, which keeps the cell firm and stores dissolved substances; - **chloroplasts**, which contain chlorophyll and are where photosynthesis takes place. Only the green parts of a plant have them, so a root cell has none. ## Bacterial cells A bacterial cell is much smaller than a plant or animal cell and has a simpler structure. Its cell wall is not made of cellulose. It has no nucleus: its genetic material lies free in the cytoplasm, and as well as this main loop of DNA it often carries one or more small rings of DNA called **plasmids**. Plasmids can be passed from one bacterium to another, and they are the structures used in genetic engineering. | Feature | Animal cell…