15.1

Drugs

Cambridge IGCSE Biology (0610)  · Unit 15: Drugs  · 9 flashcards

Drugs is topic 15.1 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 15 — Drugs .  In one line: A drug is any substance taken into the body that modifies or affects chemical reactions within the body. Examples include antibiotics, painkillers, and recreational drugs like alcohol.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 record 3 explicit questions on this topic — though the concept underpins many adjacent topics, so it is tested far more often than that figure suggests.

The deck below contains 9 flashcards — 2 definitions, 3 key concepts, 1 process card, 2 application cards and 1 identification card — covering the precise wording mark schemes reward.  Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

A drug in a biological context

A drug is any substance taken into the body that modifies or affects chemical reactions within the body. Examples include antibiotics, painkillers, and recreational drugs like alcohol.

What the Cambridge 0610 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe a drug as any substance taken into the body that modifies or affects chemical reactions in the body
  2. Describe Describe the use of antibiotics for the treatment of bacterial infections
  3. State State that some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics
  4. State State that antibiotics kill bacteria but do not affect viruses
  5. Explain Explain how using antibiotics only when essential can limit the development of resistant bacteria such as MRSA Supplement
Definition Flip

Define a drug in a biological context.

Answer Flip

A drug is any substance taken into the body that modifies or affects chemical reactions within the body. Examples include antibiotics, painkillers, and recreational drugs like alcohol.

Key Concept Flip

What type of infection are antibiotics used to treat?

Answer Flip

Antibiotics are used to treat bacterial infections. They work by interfering with bacterial cell processes, such as cell wall synthesis or protein production.

Example: penicillin treats Streptococcus infections.
Key Concept Flip

Explain why antibiotics are ineffective against viruses.

Answer Flip

Viruses have a different structure and life cycle from bacteria. Antibiotics target bacterial-specific processes, such as cell wall synthesis, which viruses lack. For instance, antibiotics won't cure influenza (flu), which is caused by the influenza virus.

Definition Flip

What is antibiotic resistance?

Answer Flip

Antibiotic resistance occurs when bacteria evolve mechanisms to survive exposure to antibiotics that would normally kill them or stop their growth. This makes infections harder to treat. An example is MRSA (Methicillin-resistant Staphylococcus aureus).

Key Concept Flip

Explain how the overuse of antibiotics can lead to antibiotic resistance.

Answer Flip

Overuse of antibiotics creates selective pressure, favoring the survival and reproduction of bacteria that are already resistant. This increases the proportion of resistant bacteria in the population.

Example: frequent antibiotic use for minor infections can promote the spread of resistant strains.
Key Concept Flip

Give an example of an antibiotic-resistant bacterium.

Answer Flip

MRSA (Methicillin-resistant Staphylococcus aureus) is a well-known example. It's a strain of Staphylococcus aureus that is resistant to many commonly used antibiotics, including methicillin.

Key Concept Flip

How does antibiotic resistance affect the treatment of bacterial infections?

Answer Flip

Antibiotic resistance reduces the effectiveness of antibiotics. Infections caused by resistant bacteria are more difficult to treat, require stronger or alternative antibiotics, and can lead to longer hospital stays and increased mortality.

Example: a urinary tract infection caused by a resistant E. coli strain.
Key Concept Flip

Describe one strategy to limit the development of antibiotic resistance.

Answer Flip

Using antibiotics only when essential is a key strategy. This reduces the selective pressure on bacteria to develop resistance. Doctors should only prescribe antibiotics for bacterial infections, and patients should complete the full course to kill all bacteria.

Key Concept Flip

Why is it important to complete the full course of antibiotics prescribed by a doctor?

Answer Flip

Failing to complete the full course of antibiotics may leave some bacteria alive. These surviving bacteria are often the most resistant and can then multiply and potentially cause a recurrence of the infection, but now with resistant bacteria.

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Key Questions: Drugs

Define a drug in a biological context.

A drug is any substance taken into the body that modifies or affects chemical reactions within the body. Examples include antibiotics, painkillers, and recreational drugs like alcohol.

What is antibiotic resistance?

Antibiotic resistance occurs when bacteria evolve mechanisms to survive exposure to antibiotics that would normally kill them or stop their growth. This makes infections harder to treat. An example is MRSA (Methicillin-resistant Staphylococcus aureus).

Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0610 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

drug medicine antibiotic painkiller depressant stimulant alcohol heroin addiction withdrawal tolerance liver damage reaction time antibiotic resistance

Key terms covered in this Drugs deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

A drug in a biological context
Antibiotic resistance

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How to study this Drugs deck

Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.