AP BIOLOGY

Detailed explanation-1: -Unlike normal cells, cancer cells don’t stop growing and dividing when there are enough of them. So the cells keep doubling, forming a lump (tumour) that grows in size.

Detailed explanation-2: -For instance, cancer cells: grow in the absence of signals telling them to grow. Normal cells only grow when they receive such signals. ignore signals that normally tell cells to stop dividing or to die (a process known as programmed cell death, or apoptosis).

Detailed explanation-3: -Most cancer cells are less adhesive than normal cells, often as a result of reduced expression of cell surface adhesion molecules. For example, loss of E-cadherin, the principal adhesion molecule of epithelial cells, is important in the development of carcinomas (epithelial cancers).

Detailed explanation-4: -The scientists studied biological changes that cells usually undergo as cancer develops. The most typical of these is the degradation of the epithelial adhesion molecule E-cadherin. In other words: the cells become less “sticky".

Detailed explanation-5: -As the tumour grows, cancer cells may fail to attach to each other, spreading through the body where they may form secondary tumours. This process is called metastasis. The diagram shows how cancer cells can invade surrounding tissue: Cancer cells are undifferentiated – they do not carry out their normal function.