Cell Structure and Function — AQA GCSE Biology
Cells are the basic units of all living things. This topic covers the parts of animal and plant cells and what each one does.
Eukaryotic and prokaryotic cells
- Eukaryotic cells (animals, plants, fungi) have a nucleus enclosing the genetic material.
- Prokaryotic cells (bacteria) are much smaller and have no nucleus — their DNA is a single loop, sometimes with extra small rings called plasmids.
Sub-cellular structures
Animal cells contain:
- Nucleus — controls the cell and holds the DNA.
- Cytoplasm — where most chemical reactions occur.
- Cell membrane — controls what enters and leaves.
- Mitochondria — site of aerobic respiration (release energy).
- Ribosomes — site of protein synthesis.
Plant cells contain all of the above, plus:
- Cell wall (made of cellulose) — strengthens the cell.
- Permanent vacuole — contains cell sap, keeps the cell rigid.
- Chloroplasts — contain chlorophyll, site of photosynthesis.
Bacterial cells contain: cytoplasm, cell membrane, cell wall, a single DNA loop and plasmids — but no nucleus, mitochondria or chloroplasts.
Linking structure to function
The structures present tell you what a cell can do — for example, a cell with many mitochondria is very active (lots of respiration), and a cell with chloroplasts can photosynthesise.
Exam tips
- Learn which structures are found in animal, plant and bacterial cells — comparison questions are common.
- Give the function of each structure, not just its name.
- Remember plant cells have everything an animal cell has plus a cell wall, vacuole and chloroplasts.
- Bacteria are prokaryotic (no nucleus); plants and animals are eukaryotic.