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This chapter section is short, factual and easy to lose marks on, because practice-question options often swap plant names, receptors and effects between the three drug groups. This post sets out the facts exactly as NCERT gives them, checks one of them with a formula, and separates two words examiners like to confuse: addiction and dependence. It is a study guide, not medical advice.
Where is it in the NEET syllabus and NCERT?
The NEET (UG) 2026 syllabus lists "Adolescence, drug and alcohol abuse. Tobacco abuse" under Biology and Human Welfare. The text is section 7.5 of the NCERT Class 12 chapter Human Health and Disease (2026-27 reprint). NCERT says the drugs most commonly abused are opioids, cannabinoids and coca alkaloids, mostly obtained from flowering plants and some from fungi.
What does NCERT say about each group?
Opioids
Bind to opioid receptors in the central nervous system and gastrointestinal tract.
Heroin, called smack, is diacetylmorphine: a white, odourless, bitter crystalline compound made by acetylating morphine.
Morphine comes from the latex of the poppy, *Papaver somniferum*.
Heroin is usually snorted or injected and is a depressant that slows body functions.
Cannabinoids
Interact with cannabinoid receptors, mainly in the brain.
Come from the inflorescences of *Cannabis sativa*; flower tops, leaves and resin give marijuana, hashish, charas and ganja.
Taken by inhalation or by mouth; known for effects on the cardiovascular system.
Coca alkaloids
Cocaine comes from *Erythroxylum coca*, native to South America.
It interferes with the transport of the neurotransmitter dopamine, and is usually snorted.
It is a potent stimulant of the central nervous system; excessive doses cause hallucinations.
The US National Institute on Drug Abuse explains the dopamine point in more detail: cocaine binds to the dopamine transporter, blocking removal of dopamine from the synapse so that it accumulates.
Worked example: does "diacetylmorphine" add up?
NCERT says heroin is made by acetylating morphine. Check it with formulas from PubChem: morphine is C₁₇H₁₉NO₃ (285.34 g/mol) and heroin is C₂₁H₂₃NO₅ (369.4 g/mol).
Each acetyl group (COCH₃) replaces the H of an –OH group, so each one adds C₂H₂O.
Two of them add C₄H₄O₂: C₁₇H₁₉NO₃ + C₄H₄O₂ = C₂₁H₂₃NO₅. The formula matches.
Mass: C₂H₂O is 2(12.011) + 2(1.008) + 15.999 = 42.04, so 285.34 + 2 × 42.04 = 369.42, which agrees with 369.4.
"Di" means two, and the arithmetic confirms two acetyl groups.
What other substances does NCERT list?
*Atropa belladonna* and *Datura*: plants with hallucinogenic properties.
Barbiturates, amphetamines and benzodiazepines: medicines for conditions such as depression and insomnia that are often abused.
Tobacco: nicotine stimulates the adrenal gland to release adrenaline and noradrenaline, raising blood pressure and heart rate; smoking raises carbon monoxide in blood and reduces haem-bound oxygen.
How is addiction different from dependence?
NCERT defines addiction as a psychological attachment to effects such as euphoria and a temporary feeling of well-being. Dependence is the tendency of the body to show a characteristic, unpleasant withdrawal syndrome if regular use stops suddenly, with anxiety, shakiness, nausea and sweating. NCERT also explains tolerance: with repeated use, receptors respond only to higher doses.
Which swaps appear in options?
Heroin called a stimulant. It is a depressant; cocaine is the stimulant.
Cocaine said to come from *Papaver*. It comes from *Erythroxylum coca*.
Cannabinoids said to act on opioid receptors. They act on cannabinoid receptors.
Morphine called harmful only. NCERT also calls it a very effective sedative and painkiller for patients after surgery.
What if this topic is more than an exam topic for you?
NCERT notes that stress from pressure to excel in examinations has pushed some young people towards alcohol and drugs, and that parents and teachers have a special role in prevention. If you or a friend is struggling, talk to someone you trust. Tele MANAS, the Ministry of Health's tele-mental health service, can be reached on 14416 or 1-800-891-4416.
A practice routine
Make three cards, one per drug group, with source plant, part used, receptor or target and effect.
Test yourself by covering one column at a time.
Write the addiction and dependence definitions from memory, then compare with NCERT.
Revise the rest of the chapter with our guide to human health, disease and immunity.
If one idea, such as how a neurotransmitter crosses a synapse, is still unclear, the Fermi Concept Library covers every concept in biology with its own lesson.
Tonight, fill in the three cards from memory and check every line against NCERT section 7.5.
