Eukaryotic cells contain organelles like a nucleus or mitochondria. Prokaryotic cells include things like bacteria that do not have separate structures within them – that is why they are so much smaller.
Signals are carried around the body by nerve cells (more properly known as neurones or neurons). The myelin sheath accelerates the impulse (the signal can jump from node to node). The one above, known as a motor neurone, carries nerve impulses to muscles. This is an example of a specialised animal cell. It still has a nucleus, cell membrane and cytoplasm but also some additional structures to help it do its job. Other examples of specialised cells include muscle cells, sperm cells and red blood cells.
The cell diagram below is a little more complex but it does give you some idea of the number of distinct structures that there are within a typical cell.
Questions…
- Name a structure you would find in a plant cell but never in an animal cell.
- Suggest a type of molecule that you would expect to find dissolved in the cytoplasm.
- What job do mitochondria perform?
- Proteins are built from amino acids. What structures tell the cell what amino acids to link together to build a specific protein?
- In the diagram of the blood cells and blood vessel, what type of vessel is shown? How can you tell?
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