Normal and sickled red blood cells

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How are cells specialised for their roles?

Each cell type is specialised for its role; specific characteristics range from making key proteins to general properties like shape. Red blood cells, for example, are small biconcave discs. This shape gives a large surface area, helping the cells to transport oxygen from the lungs to the tissues, and a little carbon dioxide the other way.

The shape also gives flexibility, helping the cells squeeze through the smallest capillaries. Developing red blood cells begin with a nucleus and organelles but lose them before they start work, which in effect reduces the cells to bags full of haemoglobin (the protein that carries oxygen and carbon dioxide). If their shape is distorted, disease can result. For example, in the inherited disease sickle-cell anaemia, some red blood cells become sickle shaped owing to abnormal haemoglobin molecules clumping together.

Organs often contain subpopulations of cells. The pancreas, for instance, makes a range of hormones and digestive enzymes. Small regions of the pancreas known as the islets of Langerhans contain four different cell types, which each make different hormones. The most common cells are beta cells, which make insulin.

How do cells specialise? A stem cell will receive signals from its surroundings that trigger a change in the pattern of genes that are turned on and off, directing the cell towards a more specialised state through the synthesis of specific proteins. Having a detailed understanding of these changes and how they are triggered may allow us to control them.

Lead image:

Sickled and normal red blood cells.

EM Unit, UCL Medical School, Royal Free Campus/Wellcome Images

Further reading

About this resource

This resource was first published in ‘The Cell’ in February 2011 and reviewed and updated in September 2015.

Cell biology, Medicine, Health, infection and disease
The Cell
Education levels:
16–19, Continuing professional development