Drugs of abuse appear in NEET as terminology-heavy recall questions. The trap is not calculation — it is confusing the drug category, the source plant/chemical, and the pharmacological effect. Get the classification grid right and these are free marks.
Three drug categories NCERT emphasises (Class 12 Biology, Chapter 7, page 142):
Opioids bind to opioid receptors in the CNS, producing sedation, pain relief, and euphoria. Heroin (diacetylmorphine, chemically derived from morphine extracted from Papaver somniferum — the opium poppy) is the most commonly tested opioid. It is smoked or injected intravenously. Morphine itself is a medically used analgesic that becomes an abuse substance when taken without prescription.
Cannabinoids interact with cannabinoid receptors in the brain. The source is Cannabis sativa — the plant yields marijuana (flower tops), hashish (resin from flower tops), and charas. These affect cardiovascular system function and are generally taken by inhalation or oral ingestion.
Coca alkaloids (cocaine) are obtained from Erythroxylum coca. Cocaine stimulates the CNS by interfering with dopamine transporter function, producing intense euphoria followed by depression. It is typically snorted; it can also be injected. NCERT lists it alongside the category of stimulants that includes amphetamines and caffeine — but cocaine's plant source is the high-frequency NEET ask.
Addiction mechanism — the NEET-relevant summary: Repeated use → tolerance (need higher dose for same effect) → psychological and physical dependence → withdrawal symptoms on cessation. NCERT stresses that adolescents are vulnerable due to peer pressure, curiosity, and the perception of enhanced academic or athletic performance.
Watch-out: NEET distractors swap source plants across categories — Papaver offered for cocaine, Erythroxylum offered for opioids. Lock the grid: opium poppy → opioids, cannabis → cannabinoids, coca plant → cocaine.
Select an option to see the explanation. Wrong answers show why your choice was tempting — and name the exact trap it exploits.
Heroin (diacetylmorphine) is chemically derived from which natural substance?
Answer: B. Heroin is diacetylmorphine — an acetylated derivative of morphine, which is extracted from the latex of Papaver somniferum (NCERT Class 12 Biology Chapter 7, page 142).
Why A is wrong: A is wrong because cannabinol is a cannabinoid compound from Cannabis sativa, not related to heroin's synthetic pathway.
Why C is wrong: C is wrong because cocaine is a separate stimulant alkaloid from Erythroxylum coca — it is not the precursor of heroin.
Why D is wrong: D is wrong because caffeine is a mild CNS stimulant found in tea and coffee — it has no chemical relationship to opioid synthesis.
Which plant is the source of cannabinoids such as marijuana and hashish?
Answer: D. Marijuana, hashish, and charas are all derived from Cannabis sativa (NCERT Class 12 Biology Chapter 7, page 143).
Why A is wrong: A is wrong because Papaver somniferum is the opium poppy — source of opioids (morphine, heroin), not cannabinoids.
Why B is wrong: B is wrong because Erythroxylum coca yields cocaine, a stimulant alkaloid — not cannabinoids.
Why C is wrong: C is wrong because Atropa belladonna produces atropine, an anticholinergic — it is not associated with cannabinoids.
Cocaine, a CNS stimulant drug of abuse, is obtained from:
Answer: A. Cocaine is an alkaloid extracted from Erythroxylum coca (NCERT Class 12 Biology Chapter 7, page 143).
Why B is wrong: B is wrong because Papaver somniferum yields opioids (morphine → heroin), not coca alkaloids.
Why C is wrong: C is wrong because Cannabis sativa is the source of cannabinoids (marijuana, hashish), not cocaine — a common NEET plant-swap distractor.
Why D is wrong: D is wrong because Coffea arabica is the source of caffeine — a mild stimulant, not cocaine.
An adolescent develops tolerance to a drug, requiring progressively higher doses to achieve the same effect. This phenomenon is a hallmark of:
Answer: D. Tolerance — needing increased doses for the same pharmacological effect — is a defining feature of drug addiction and dependence (NCERT Class 12 Biology Chapter 7, page 145).
Why A is wrong: A is wrong because allergy is an exaggerated immune response to an antigen — it involves hypersensitivity, not dose escalation for a desired effect.
Why B is wrong: B is wrong because withdrawal syndrome refers to symptoms upon cessation of drug use — it is a consequence of dependence, not the same phenomenon as tolerance.
Why C is wrong: C is wrong because innate immunity is the body's non-specific first line of defence — it is unrelated to drug-dose escalation.
A person who abruptly stops taking an opioid after prolonged use experiences nausea, anxiety, and tremors. This clinical presentation is best described as:
Answer: C. Withdrawal syndrome is the set of unpleasant physical and psychological symptoms that appear when a dependent person stops taking the drug abruptly (NCERT Class 12 Biology Chapter 7, page 145).
Why A is wrong: A is wrong because tolerance is the need for increasing doses — not the symptom complex upon drug cessation.
Why B is wrong: B is wrong because anaphylaxis is an acute, severe allergic reaction mediated by IgE — not a drug-dependence phenomenon.
Why D is wrong: D is wrong because autoimmunity is the immune system attacking self-tissues — it has no connection to drug withdrawal.
A student claims that hashish and charas are obtained from different plant species. Which correction is appropriate?
Answer: A. Hashish (resinous extract of flower tops) and charas are both derived from Cannabis sativa. They differ in preparation method, not plant source (NCERT Class 12 Biology Chapter 7, page 143).
Why B is wrong: B is wrong because neither hashish nor charas comes from Erythroxylum coca — that plant yields cocaine.
Why C is wrong: C is wrong because Papaver somniferum is the opium poppy (source of opioids), not cannabinoids.
Why D is wrong: D is wrong because hashish is a natural resin extract from Cannabis sativa, not a synthetic product.
Among the following, which correctly matches the drug category with its primary pharmacological mechanism?
Answer: B. Cannabinoids (from Cannabis sativa) exert their effects by binding to cannabinoid receptors present in the brain (NCERT Class 12 Biology Chapter 7, page 143).
Why A is wrong: A is wrong because opioids bind to opioid receptors in the CNS — blocking dopamine reuptake is the mechanism of cocaine, not opioids.
Why C is wrong: C is wrong because cocaine interferes with dopamine transport (stimulant action) — it does not bind opioid receptors. This is a mechanism-swap distractor.
Why D is wrong: D is wrong because morphine is an opioid that binds opioid receptors — it does not interact with cannabinoid receptors.
NCERT lists peer pressure, curiosity, and desire for enhanced performance as factors making adolescents vulnerable to drug abuse. Which of the following interventions aligns with the preventive measures described in NCERT?
Answer: C. NCERT emphasises that adolescents should be educated, encouraged to seek guidance from trusted adults, and channelled toward healthy activities like sports and hobbies as preventive strategies (NCERT Class 12 Biology Chapter 7, pages 146–147).
Why A is wrong: A is wrong because prescribing opioids for tolerance-building is medically and ethically inappropriate — it would create dependence, not prevent it.
Why B is wrong: B is wrong because NCERT explicitly advocates drug education and awareness as a preventive measure — avoidance of education increases vulnerability.
Why D is wrong: D is wrong because self-medication with any stimulant is not a recognised preventive strategy — it could itself lead to dependence.
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Given
A NEET question states: "Diacetylmorphine is obtained from which of the following?" Options: (A) Erythroxylum coca, (B) Cannabis sativa, (C) Papaver somniferum, (D) Atropa belladonna.
Required
Identify the correct source plant for diacetylmorphine.
Concept
Diacetylmorphine is the chemical name for heroin. Heroin is synthesised by acetylation of morphine. Morphine is a natural opioid alkaloid extracted from the latex of the opium poppy.
Formula
No formula required — this is a recall-classification question.
Substitution
Diacetylmorphine → heroin → derived from morphine → morphine comes from Papaver somniferum.
Calculation
No arithmetic. The chain is: diacetylmorphine = heroin = acetylated morphine. Morphine source = Papaver somniferum.
Final answer
(C) Papaver somniferum
Common trap
The most common distractor here is Erythroxylum coca (option A) — students who have memorised that cocaine is also a drug of abuse sometimes swap the plant source. Lock the pairing: coca plant → cocaine; opium poppy → opioids.
Similar NEET-style question
"Which of the following is the source of charas and hashish?" (A) Papaver somniferum, (B) Erythroxylum coca, (C) Cannabis sativa, (D) Datura stramonium. Answer: (C). Same distractor pattern — plant-source swap.
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Opioids (heroin, morphine — analgesic); cannabinoids (THC — marijuana); cocaine (CNS stimulant); coca alkaloids; tobacco (nicotine — addictive). Withdrawal symptoms; tolerance; psychological/physical dependence.
-- NCERT Class 12 Biology, Ch. 7, p. 142More in Biology and Human Welfare: 4 exam traps and mistakes · 1 question pattern from its other lessons.
3 questions from NEET 2023, 2024, 2026. Answers verified against NTA official keys.
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