Cell shapes and structure varies due to function. Each cell is specialised to carry out a specific function. This means some cells won’t have all of the organelle of a generalised cell and sometimes have extra organelles.
A red blood cells primary function is to carry oxygen from the lungs to every cell in the body for respiration. Any organelles that are not helpful for this function are missing. Looking at diagram 2 of a RBC we can see that the red blood cell has very few organelle including no nucleus. With all these missing organelle there’s more space for more haemoglobin, the substance carries oxygen. With more haemoglobin the cell can carry more oxygen at once and be more efficient at its job. Its biconcave disc shape that gives it a greater surface area, which means there is more space to carry more oxygen. They also have flexible membranes so they can bend easily to pass through the tiniest blood vessels without breaking. (Roberts, 1986)
Another specialised cell is a white blood cell. A white blood cells function is to fight infection and destroy foreign bodies. To do this job the cell has a flexible membrane, which gives it an irregular shape. This flexi membrane enables the cell to surround the bacteria before it releases its many lysosomes to digest the toxins. A white blood cell has a nucleus so it can reproduce itself and increase their numbers to fight off infection more quickly. In order to get to the bacteria quickly the cell needs energy, so the cell has mitochondria to produce this.
A sperm cell is another cell specialised to do a task, to fertilise the egg cell. A sperm cell is a very small and has very few organelles. Only containing what’s essential to carry out its task and to reduce energy demand. (See diagram 4). It has a predominant head shape, being the nucleus, which carries the fathers DNA to be passed onto the unfertilised egg. Unlike a generalised cell it has a flagellum (a tail)
to enable the sperm to swim to the egg. The distance to the egg is a long journey
for such a small cell that has to power its movement itself. In order to do so there is a need for many more mitochondria, which are situated in the mid section of the cell. At the front of the cell is the acrosome. This contains an enzyme, which breaks down the egg wall in order for the sperm to enter and fertilise the egg.
(Vander, Sherman, Luciano, l994)
Probably the most complex specialised cell is a motor neurone. Diagram 5 shows the structure of a motor neurone .The function of a motor neurone is to transmit nervous impulses to different parts of the body. Like a standard cell there is a cell body (soma), which is like the factory of the neurone, it contains the same organelle as a generalised cell and performs in the same way. However attached to this cell body is lots of little dendrites. These dendrites act as ‘antennae’ to receive signals from other connected nerves cells.
The axon is the conduction part of the neurone. It’s a long fibre that transmits the impulse from the cell body as electrical signals that may split to several branches to transmit messages to different organs or muscles. Around the axon is myelin sheath that protects the axon and stops interference with other axons.
At junctions with other nerve cells and the target are end plates. These are the sites where the synapses are formed.
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