Commonly abused drugs and tobacco · Biology Class 11–12 | StemPy Lab
Course 25.3·Lesson 2 of 3
Commonly abused drugs and tobacco
The commonly abused drugs are the opioids, the cannabinoids and the coca alkaloids, and most come from flowering plants. Heroin is made from the morphine of the opium poppy, cannabinoids come from hemp and cocaine from the coca plant. Nicotine and carbon monoxide in tobacco smoke harm the heart and the blood, and the smoke causes cancer and lung disease.
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Drugs: medicine or abuse?
A doctor may give morphine to a patient after a big operation to remove pain. The same drug used by a person without a doctor can wreck his life. What is the difference?
A drug is a chemical that changes how the body or the mind works. Many drugs are valuable medicines. Drug abuse is the use of a drug for non-medical reasons, in an amount and at a frequency that harm the physical, mental and social health.
NCERT says that the drugs that are commonly abused are the opioids, the cannabinoids and the coca alkaloids. Most of them come from flowering plants. A few come from fungi.
A table of three rows with three columns: the plant, the source or product, and the receptors and action. Row 1: the opium poppy, Papaver somniferum. Its latex gives morphine, and acetylation gives heroin, also called smack. It acts on opioid receptors in the brain and the gut, and is a depressant that slows the body down. Row 2: the hemp plant, Cannabis sativa. The flower tops, leaves and resin give marijuana, hashish, charas and ganja. It acts on cannabinoid receptors, mostly in the brain, and the cardiovascular system is affected. Row 3: the coca plant, Erythroxylum coca, of South America. It gives cocaine, also called coke or crack. It interferes with the transport of dopamine, and is a stimulant that gives euphoria, and large doses cause hallucinations. A line at the bottom says that Atropa belladonna and Datura are other plants with a hallucinogenic action.
Opioids
Opioids bind to opioid receptors in the central nervous system and in the gastrointestinal tract.
Morphine is taken from the latex of the poppy plant Papaver somniferum. It is a very effective sedative and painkiller that doctors use after surgery.
Heroin (smack) is diacetylmorphine. It is a white, odourless, bitter crystalline compound, made by the acetylation of morphine. It is generally taken by snorting or by injection.
Heroin is a depressant: it slows down the functions of the body.
Cannabinoids
Cannabinoids bind to cannabinoid receptors, found mainly in the brain.
The natural ones come from the flower tops, leaves and resin of the plant Cannabis sativa. They are used to make marijuana, hashish, charas and ganja.
They are generally taken by inhaling or swallowing. They affect the cardiovascular system.
Some sportspersons abuse them.
Coca alkaloids
Cocaine, also called coke or crack, comes from the coca plant Erythroxylum coca, which is native to South America.
Cocaine interferes with the transport of the neurotransmitter dopamine. It is usually snorted.
It is a stimulant: it gives a feeling of euphoria and more energy. Large doses cause hallucinations, in which a person sees or hears things that are not there.
Other drugs
Atropa belladonna and Datura are plants with a hallucinogenic action. Drugs such as barbiturates, amphetamines, benzodiazepines and LSD are medicines for mental illnesses such as depression and sleeplessness. They are abused too.
Some sportspersons abuse narcotic analgesics, anabolic steroids, diuretics and certain hormones to build muscle and to become more aggressive. These drugs damage the body, cause mood swings and are banned in sport.
Tobacco
Tobacco is smoked, chewed or sniffed. It holds the alkaloid nicotine.
Nicotine stimulates the adrenal glands to release adrenaline and noradrenaline. They raise the blood pressure and the heart rate.
Carbon monoxide in the smoke binds to haemoglobin and reduces its hold on oxygen. The blood carries less oxygen, and the body gets too little.
Smoking increases the risk of cancer of the lung, the urinary bladder and the throat, and of bronchitis, emphysema, coronary heart disease and gastric ulcer.
Chewing tobacco increases the risk of cancer of the oral cavity.
A flow diagram. A box on the left, tobacco smoke, has three arrows leading to three boxes. The first box, nicotine, leads to the note that the adrenal glands release adrenaline and noradrenaline, so the blood pressure and the heart rate rise. The second box, carbon monoxide, leads to the note that it binds to haemoglobin, so the blood carries less oxygen and the body gets too little oxygen. The third box, tar and other carcinogens, leads to the note that they cause cancer of the lung, throat and urinary bladder, and also bronchitis and emphysema.
You should find that the oxygen capacity falls in a straight line as more of the haemoglobin is held by carbon monoxide. The model is a simple picture. Carbon monoxide also makes the remaining oxygen harder to release to the tissues.
The value 1.34 mL of oxygen for each gram of haemoglobin is a standard textbook value. NCERT does not give it.
Try it in Python
The program works out the oxygen that the blood can carry.
Practise with new numbers
Common mistakes
Saying that morphine and heroin are the same substance. Heroin is made from morphine by acetylation.
Saying that cocaine comes from the poppy. It comes from the coca plant. Morphine comes from the poppy.
Saying that cocaine slows the body down. It is a stimulant. Heroin is a depressant.
Saying that smoking harms only the lungs. It also harms the heart and the blood vessels, and raises the risk of cancers of the bladder and the throat.
Saying that nicotine lowers the heart rate. It raises the blood pressure and the heart rate.
Remember these
Commonly abused drugs: opioids, cannabinoids and coca alkaloids.
Morphine and heroin: from the latex of Papaver somniferum. Heroin is made by the acetylation of morphine. Heroin is a depressant.
Cannabinoids: Cannabis sativa, which gives marijuana, hashish, charas and ganja. They act on cannabinoid receptors in the brain.
Cocaine: Erythroxylum coca, a stimulant that interferes with dopamine transport.
Tobacco: nicotine raises the blood pressure and the heart rate. Carbon monoxide reduces the oxygen carried. The smoke causes cancer.
Check yourself
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
From which plant is morphine obtained, and how is heroin made from it?
Name the plant and the products that give the cannabinoids.
How does cocaine act on the nervous system?
Why does a heavy smoker have less oxygen in the tissues?
What does nicotine do to the heart rate and the blood pressure, and how?
References
Hall J. E. and Hall M. E. (2021). Guyton and Hall Textbook of Medical Physiology, 14th edition, Elsevier, the chapter on the transport of oxygen.
World Health Organization (2023). Fact sheets: Tobacco; Opioid overdose; Cannabis.
NCERT (2023). Biology, Textbook for Class XII, chapter 7.
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