Human Health and Disease — BIOLOGY STD 12 Science — Question

(i) Contact inhibition : In our body, cell growth and differentiation is highly controlled and regulated. In cancer cells, there is breakdown of these regulatory mechanisms. Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth.
(ii) Difference between benign tumors and malignant tumors :

S.No.	Benign Tumors	Malignant Tumors
1	It is a non-cancerous tumor.	Whereas it is a cancerous tumor.
2	They normal remain confined to their original location.	Whereas it is not confined to its original location.
3	Metastasis property is not found.	Metastasis property is found in these.
4	Cause little damage to body.	Cause more damage to body.

(iii) Cause of cancer : The chemical carcinogens present in tobacco smoke have been idetified as a major cause of lung cancer.