Uncontrolled Cell Division (Edexcel GCSE Biology)

Uncontrolled Cell Division

• Cells in the body divide by mitosis to produce more cells - this is essential for growth and to repair damaged cells

  • For example, the cells of the intestines are constantly dividing to replace those that are shed as food moves through the digestive system

• Mitosis is just one part of the cell cycle which is regulated by many different genes to ensure that cells divide only when they need to and stop when required

• Cancer is caused as a result of mutations in the DNA of cells that lead to uncontrolled cell growth and division - this can result in the formation of a tumour (a mass of cells)

  • Usually, tumours form as a result of loss of control of the cell cycle

Types of Tumour

• There are two main types of tumour:

  • Benign tumours

  • Malignant tumours

• Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane

  • Crucially, benign tumours do not invade other parts of the body

  • This means these tumours are not considered cancerous

• Malignant tumours are cancerous – the cells of these tumours invade neighbouring tissues and spread to different parts of the body via the blood and lymphatic system where they form secondary tumours

  • Malignant tumours are more likely to disrupt the functioning of the organ they originate in (as they invade healthy tissue) and the organs they spread to – this is why they are dangerous and how they lead to death