How do antibiotics work, why is resistance a problem, and how do drugs affect health?
How antibiotics treat bacterial but not viral infections, the problem of antibiotic resistance and how to reduce it, how new medicines are tested, and the effects of legal and illegal drugs including alcohol and tobacco.
A focused CCEA GCSE Double Award Science (Biology Unit B2) answer on medicines and drugs, covering how antibiotics treat bacterial not viral infections, antibiotic resistance and reducing it, how new medicines are tested, and the effects of alcohol, tobacco and other drugs on health.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this dot point is asking
CCEA Double Award wants how antibiotics work and why they do not treat viruses, the problem of antibiotic resistance and how to reduce it, how new medicines are tested, and the effects of drugs including alcohol and tobacco. The antibiotic and resistance material links directly to natural selection.
How antibiotics work
Viruses reproduce inside the body's own cells, so antibiotics cannot reach them without harming the cells. That is why a cold or flu (viral) cannot be treated with antibiotics. Painkillers can ease the symptoms of a viral illness but do not kill the virus.
Antibiotic resistance
Overusing or misusing antibiotics drives antibiotic resistance. By natural selection, a chance mutation makes a few bacteria resistant; the antibiotic kills the rest, the resistant survivors reproduce, and the population becomes resistant. Resistant strains such as MRSA are hard to treat.
To slow resistance:
- Doctors should prescribe antibiotics only when needed (not for viral infections), reducing the selection pressure.
- Patients should finish the full course, so all the bacteria are killed and resistant ones do not survive.
- Antibiotics should be used carefully in farming.
Testing new medicines
New medicines are tested before they can be used, to check they are safe and effective. Testing moves from laboratory tests (often on cells and then animals) to clinical trials on healthy volunteers and then patients, checking for safety, the correct dose and side effects. Only medicines that pass are approved.
Drugs and health
A drug is a substance that changes how the body works. Some are medical; others are recreational and can be harmful or addictive.
- Alcohol is a depressant that slows reactions and judgement; long-term use damages the liver (cirrhosis) and the brain.
- Tobacco smoke contains nicotine (addictive), tar (causes lung cancer and bronchitis) and carbon monoxide (reduces oxygen carried by the blood). Smoking is linked to heart and lung disease.
Examples in context
Example 1. MRSA in hospitals. MRSA is a bacterium resistant to many antibiotics, which spread in hospitals where antibiotics are used heavily. Strict hygiene and careful antibiotic use are needed to control it, showing resistance as a real-world problem.
Example 2. Why smokers' babies can be smaller. Carbon monoxide from tobacco smoke reduces the oxygen the mother's blood can carry, so the developing baby gets less oxygen and may grow more slowly. This links tobacco's effects to the circulatory system.
Try this
Q1. What type of pathogen do antibiotics treat? [1 mark]
- Cue. Bacteria.
Q2. Name one harmful substance in tobacco smoke and its effect. [1 mark]
- Cue. Tar (causes lung cancer), or carbon monoxide (reduces oxygen carried).
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA-style3 marksExplain why antibiotics cannot be used to treat a cold.Show worked answer →
Link the type of pathogen to the action of the antibiotic for three marks.
A cold is caused by a virus, not a bacterium.
Antibiotics work by killing bacteria or stopping them growing; they have no effect on viruses.
Viruses reproduce inside the body's own cells, so antibiotics cannot reach them without harming the cells. Markers want a cold being viral and antibiotics only working on bacteria.
CCEA-style4 marksDescribe two ways to reduce the development of antibiotic resistance.Show worked answer →
Two valid measures with reasons for four marks.
Doctors should only prescribe antibiotics when they are really needed, not for viral infections, to reduce the selection pressure.
Patients should always finish the full course, so all the bacteria are killed and resistant ones do not survive to reproduce.
Other answers include using antibiotics correctly in farming. Markers reward two sensible measures each with a brief reason.
Related dot points
- The main types of microorganism and their useful roles, pathogens and how they spread, the body's first-line defences, the role of white blood cells in phagocytosis and antibody production, and how vaccination gives immunity.
A focused CCEA GCSE Double Award Science (Biology Unit B2) answer on microorganisms and defence, covering the types of microorganism and their uses, pathogens and how they spread, first-line defences, white blood cells and phagocytosis and antibodies, and how vaccination provides immunity.
- Continuous and discontinuous variation and their genetic and environmental causes, the role of mutation, the theory of evolution by natural selection, antibiotic resistance as an example, and the evidence from fossils.
A focused CCEA GCSE Double Award Science (Biology Unit B2) answer on variation and evolution, covering continuous and discontinuous variation, genetic and environmental causes, mutation, natural selection, antibiotic resistance as an example, and fossil evidence.
- The components of the blood and their functions, the structure of the heart with its chambers and valves, the double circulatory system, the structure and adaptations of arteries, veins and capillaries, and the effect of lifestyle on heart health.
A focused CCEA GCSE Double Award Science (Biology Unit B2) answer on the circulatory system, covering the components of blood, the structure of the heart and its valves, the double circulation, the adaptations of arteries, veins and capillaries, and lifestyle effects on heart health.
- The structure of the human respiratory system, the mechanism of breathing in and out, gas exchange in the alveoli and their adaptations, the difference between breathing and respiration, and aerobic and anaerobic respiration.
A focused CCEA GCSE Double Award Science (Biology Unit B1) answer on breathing and respiration, covering the respiratory system, the mechanism of breathing, gas exchange in the alveoli, the difference between breathing and respiration, and aerobic and anaerobic respiration with their equations.
- The relationship between the nucleus, chromosomes, genes and DNA, the structure of DNA as a double helix with complementary base pairs, the human chromosome number, and how a gene codes for a protein.
A focused CCEA GCSE Double Award Science (Biology Unit B2) answer on genetic material, covering the relationship between the nucleus, chromosomes, genes and DNA, the double helix and complementary base pairs, the human chromosome number, and how a gene codes for a protein.
Sources & how we know this
- CCEA GCSE Science Double Award specification — CCEA (2017)