Animal and plant cellsSpec 1.1
Animal and plant cells are eukaryotic cells. Their genetic material is enclosed in a nucleus. Each structure inside a cell, called a sub-cellular structure, has a job, and you need to link each structure to its function.
| Structure | Function | Animal cell | Plant cell |
|---|---|---|---|
| Nucleus | Contains the genetic material (DNA) and controls the activities of the cell | Yes | Yes |
| Cell membrane | Controls the movement of substances into and out of the cell | Yes | Yes |
| Mitochondria | Where aerobic respiration takes place, releasing energy for the cell | Yes | Yes |
| Ribosomes | Where proteins are made (protein synthesis) | Yes | Yes |
| Cell wall | Made of cellulose. Strengthens the cell and supports it | No | Yes |
| Chloroplasts | Contain chlorophyll, which absorbs light for photosynthesis | No | Yes |
| Vacuole | Contains cell sap, a solution of sugars and salts, and helps keep the cell firm | No | Yes |
Plant cells have three structures that animal cells do not: a cell wall, chloroplasts and a vacuole. Chloroplasts are only found in the green parts of a plant that photosynthesise, such as leaf cells.
Tap to enlargeBacterial cellsSpec 1.1
Bacteria are prokaryotic cells. They do not have a nucleus. Their genetic material is found free in the cytoplasm.
- Chromosomal DNA
- A single loop of DNA found free in the cytoplasm, not enclosed in a nucleus.
- Plasmid DNA
- Small rings of extra DNA, separate from the chromosomal DNA.
- Cell membrane
- Controls the movement of substances into and out of the cell.
- Ribosomes
- Where proteins are made.
- Flagellum
- A long, whip-like structure that moves to make the bacterium swim. Some bacteria have one or more flagella.
| Feature | Eukaryotic cell (animal, plant) | Prokaryotic cell (bacterium) |
|---|---|---|
| Nucleus | Present, contains the DNA | Absent |
| Where the DNA is | Inside the nucleus | Free in the cytoplasm |
| Plasmids | Not present | Often present |
| Mitochondria | Present | Absent |
| Flagella | Not present | Present in some |
Tap to enlargeSpecialised cellsSpec 1.2
A specialised cell has features, called adaptations, that help it do its job. You need to describe how sperm cells, egg cells and ciliated epithelial cells are adapted.
Sperm cells
The job of a sperm cell is to reach an egg cell and fuse with it at fertilisation.
| Adaptation | How it helps |
|---|---|
| Acrosome | Contains digestive enzymes that break down the outer layers of the egg cell so the sperm can get in |
| Haploid nucleus | Contains half the number of chromosomes of a normal body cell, so fertilisation restores the full number |
| Many mitochondria | Release energy by aerobic respiration for the tail to move |
| Tail | Moves from side to side to push the sperm along, so it can swim to the egg |
Egg cells
| Adaptation | How it helps |
|---|---|
| Nutrients in the cytoplasm | A food store that supplies the early embryo with nutrients and energy to grow |
| Haploid nucleus | Contains half the number of chromosomes, which join with the sperm nucleus at fertilisation |
| Changes in the cell membrane after fertilisation | The membrane changes straight after a sperm enters, so no more sperm can get in |
Ciliated epithelial cells
These cells line parts of the airways. Their surface has cilia, tiny hair-like projections. The cilia beat together and move mucus, which has trapped dust and microorganisms, away from the lungs.
Tap to enlargeQuick check
Name the three structures found in plant cells but not in animal cells.
Show answer
Cell wall, chloroplasts and vacuole.
Where is the DNA in a bacterial cell?
Show answer
Free in the cytoplasm, as chromosomal DNA and plasmid DNA. There is no nucleus.
What is the function of the acrosome?
Show answer
It contains enzymes that digest the outer layers of the egg.
Why does a sperm cell have a haploid nucleus?
Show answer
It has half the chromosomes, so fusing with the egg nucleus gives the full number.
What do the cilia on ciliated epithelial cells do?
Show answer
They move mucus containing trapped dust and microorganisms away from the lungs.