Q1.
How do cancer cells grow and spread?
Answer
They grow because they have lost the controls that stop normal cell division, and they spread by invading nearby tissues and travelling to other parts of the body.
normal cell: grow → work → age → die → replaced, all under control
cancer cell: control system breaks down
→ divides uncontrollably, ignores contact inhibition
→ mass of abnormal cells = tumour (benign or malignant)
→ malignant tumour invades nearby tissues
→ cells travel and form new tumours elsewhere
cancer cell: control system breaks down
→ divides uncontrollably, ignores contact inhibition
→ mass of abnormal cells = tumour (benign or malignant)
→ malignant tumour invades nearby tissues
→ cells travel and form new tumours elsewhere
| Benign tumour | Malignant (cancerous) tumour | |
|---|---|---|
| Growth | Stays as one local mass | Invades the surrounding tissue |
| Spread to other organs | No | Yes — forms new tumours elsewhere |
| Danger | Usually low, unless it presses on an organ | High |
Why it happens: in many animal cells, division normally stops when a cell comes into contact with its neighbours — contact inhibition. A cancer cell no longer obeys that signal, so it keeps dividing even when there is no room. It also escapes the normal instruction to die at the end of its life span. The result is a growing mass which takes food and oxygen away from healthy tissue, and, if malignant, breaks through the boundaries between tissues and is carried to distant organs. Plant cells, by contrast, do not show contact inhibition at all — their rigid cell walls hold them in place and they follow a different pattern of growth, which is why the question of a spreading tumour does not arise in plants in the same way.