Specialised cells
Specialised cells
- Unit 1: Cells
- Unit 2: Organisms
- Unit 3: Microorganisms
- Unit 4: Digestion and excretion
- Unit 5: Respiration
- Unit 6: Circulatory System
- Unit 7: Nervous System
- Unit 8: Senses
- Unit 9: Musculoskeletal
Some specialised animal cells
Not all of the cells in your body are the same. There are many different kinds of cell in your body. Each kind of cell has a particular function. The function of a cell is the job that it does, or the role that it plays.
Each cell is specialised to carry out its function. This means that it has a structure that helps it to do its function really well. The cell is adapted to carry out its function.
The diagrams show three kinds of specialised cell in the human body.
Red blood cells are smaller than most other cells in the body. This allows them to get through tiny blood capillaries, so they can deliver oxygen to every part of the body.
The cytoplasm contains a red pigment (colour) called haemoglobin. This carries oxygen around the body.
The cell has no nucleus. This leaves more space for haemoglobin.
Neurones carry electrical signals from one part of the body to another. They help all the different parts of the body to communicate with each other. For example, they can carry signals from the brain to muscles, to make the muscles move.
The axon is a very long strand of cytoplasm. Electrical signals can travel along this very quickly.
Dendrites are short strands of cytoplasm that collect electrical signals from other nearby nerve cells.
Ciliated cells have tiny threads along one edge, like microscopic hairs. These are called cilia. The cilia can move.
One place in the body that contains ciliated cells is the lining of the tubes leading from your mouth to your lungs.
Other cells in this lining make a sticky substance called mucus. When you breathe in, the mucus traps dust and bacteria in the air, to stop them going into your lungs. The cilia sweep the mucus up to the back of your mouth and you swallow it.
Questions
List two things that red blood cells, neurones and ciliated cells have in common.
Show Answer
All three cells have a cell membrane and cytoplasm. These are features common to animal cells.
How can you tell that all of these three cells are animal cells, not plant cells?
Show Answer
They do not have a cell wall or chloroplasts, which are found in plant cells. Their shapes are also more flexible or irregular, typical of animal cells.
Some specialised plant cells
Plants also contain specialised cells. Here are two examples.
Root hair cells are found on the outside of plant roots.
Their function is to absorb (soak up) water from the soil.
Each cell has a long, thin extension that allows water to move easily from the soil into the cell.
Palisade cells are found in the leaves of plants. Their function is to make food by photosynthesis.
They have a lot of chloroplasts containing chlorophyll.
The chlorophyll absorbs energy from sunlight, which is used to help the plant make food.
Questions
Suggest why root hair cells do not contain chloroplasts.
Show Answer
Root hair cells are underground and do not receive sunlight, so they do not need chloroplasts, which are used for photosynthesis.
Water moves through several parts of the root hair cell, as it goes from the soil into the sap vacuole. List these parts, in order.
Show Answer
Cell wall → cell membrane → cytoplasm → large vacuole with cell sap.