Cancer, Drugs and Alcohol Abuse: Quick Revision

A brief note on Cancer, Drugs and Alcohol Abuse. Read it before a test. Try each question at the end before you open its answer.

Cancer

• Contact inhibition: normal cells stop dividing on contact. Cancer cells lose it and form a tumour.
• Benign tumour: stays at its site and does little damage. Malignant tumour: invades, and its cells spread by metastasis.
• Carcinogens: physical (X-rays, gamma rays, UV), chemical (tobacco smoke, the main cause of lung cancer) and biological (oncogenic viruses with viral oncogenes).
• Proto-oncogenes are normal genes. They become oncogenes when activated.
• Detection: biopsy and histopathology, blood and bone marrow tests, X-rays, CT, MRI, antibodies and molecular tests.
• Treatment: surgery, radiation therapy, chemotherapy (hair loss and anaemia), immunotherapy (α-interferon).

Drugs and tobacco

• Opioids: morphine from the latex of Papaver somniferum. Heroin, made by acetylation, is a depressant. They act on opioid receptors.
• Cannabinoids: Cannabis sativa: marijuana, hashish, charas, ganja. They act on cannabinoid receptors in the brain.
• Cocaine: Erythroxylum coca, a stimulant that interferes with the transport of dopamine.
• Tobacco: nicotine raises the blood pressure and the heart rate through adrenaline and noradrenaline. Carbon monoxide lowers the oxygen carried. The smoke causes cancers of the lung, urinary bladder and throat, and chewing causes oral cancer.

Addiction and prevention

• Reasons: curiosity, adventure, peer pressure, stress and family history.
• Addiction: a psychological attachment. Dependence: the withdrawal syndrome if the dose is stopped.
• Alcohol: damages the nervous system and the liver. Sharing needles spreads AIDS and hepatitis B.
• Prevention: avoid peer pressure, education and counselling, help from parents and peers, danger signs, professional help.

A worked example

100 mL of blood holds 15 g of haemoglobin. How much oxygen can it carry, at 1.34 mL for each gram, if 10 per cent of the haemoglobin holds carbon monoxide?

1. The full capacity is $1.34 \times 15 = 20.1$ mL.
2. The free share is 90 per cent, so the capacity is $0.90 \times 20.1 = 18.1$ mL.

Practice with new numbers

A program to try

The program finds how many doublings take one cell to a billion cells.

Mistakes to avoid

• Saying that every tumour is cancer. A benign tumour is not.
• Saying that cocaine comes from the poppy. It comes from the coca plant.
• Mixing up addiction and dependence. Dependence means that withdrawal signs appear when the dose is stopped.
• Saying that chewing tobacco causes lung cancer. It raises the risk of cancer of the oral cavity.

Check yourself

1. What is metastasis?

2. Which hormones does nicotine release?

3. How is heroin made from morphine?

4. Name one danger sign in an adolescent.

Sources

• World Health Organization (2024). Fact sheets: Cancer; Tobacco.
• NCERT (2023). Biology, Textbook for Class XII, chapter 7.