Test: Classification of Drugs & their Target Interaction (Old NCERT) - NEET MCQ

• Drugs are chemicals of low molecular masses (≈100–500u). 
• These interact with macromolecular targets and produce a biological response. 
• When the biological response is therapeutic and useful, these chemicals are called medicines and are used in the diagnosis, prevention and treatment of diseases. 
• If taken in doses higher than those recommended, most of the drugs used as medicines are potential poisons.

Hence the correct option is A.

• Chemotherapy is a drug treatment that uses powerful chemicals to kill fast-growing cells in your body.
• Chemotherapy is most often used to treat cancer since cancer cells grow and multiply much more quickly than most cells in the body.
• Many different chemotherapy drugs are available.

Narcotics are habit-forming or addictive analgesic drugs. Analgin is a non-addictive analgesic.

Additional Information: Drugs are chemical substances that affect or alter physiology when taken into a living system. They can either be natural or synthetic.

Out of all the options given, Analgin is not a narcotic drug. However, it is a non-steroidal anti-inflammatory drug. 

• Neurotransmitters are often referred to as the body's chemical messengers.
• They are the molecules used by the nervous system to transmit messages between neurons, or from neurons to muscles.
• Communication between two neurons happens in the synaptic cleft (the small gap between the synapses of neurons).
• Serotonin, glutamine and histamine are some examples. 

Aspirin (Acetylsalicylic acid) is a chemical substance which lowers body temperature(antipyretic property) and reduces pain as well(analgesic property). Therefore it acts both as an analgesic and antipyretic.

• Drugs that mimic the natural messenger by switching on the receptor, are called agonists.
• These are useful when there is a lack of natural chemical messenger.
• Examples: oxycodone, methadone, hydrocodone, morphine, opium and others.

• An enzyme inhibitor is a molecule that binds to an enzyme and decreases its activity.
• Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors.
• They are also used in pesticides.

• Sulphonamides are drugs which share common structural features and often have similar pharmacological activity.
• A sulfonamide is a functional group (a part of a molecule) that is the basis of several groups of drugs, which are called sulphonamides, sulfa drugs or sulpha drugs.
• The original antibacterial sulfonamides are synthetic (nonantibiotic) antimicrobial agents that contain the sulfonamide group.
• Some sulfonamides are also devoid of antibacterial activity. 

• Drugs that bind to the receptor site and inhibit its natural function are called antagonists.
• These are useful when blocking the message is required.
•  Some examples of antagonists are naloxone, naltrexone, and Quisqualic acid.

• The range of bacteria or other microorganisms that are affected by a certain antibiotic is expressed as its spectrum of action.
• Antibiotics that kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are said to be broad-spectrum antibiotics.
• Chloramphenicol,Vancomycin and ofloxacin are important broad-spectrum antibiotics.