How do antibiotics and other medicines work, and why is drug misuse harmful?
How antibiotics treat bacterial infections but not viral ones, the problem of antibiotic resistance and how to reduce it, the difference between medical and recreational drugs, and the effects of alcohol and tobacco on health.
A focused CCEA GCSE Biology answer on medicines and drugs, covering how antibiotics treat bacteria but not viruses, antibiotic resistance and how to reduce it, medical versus recreational drugs, and the effects of alcohol and tobacco.
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What this dot point is asking
CCEA wants you to explain how antibiotics treat bacterial infections but not viral ones, describe the problem of antibiotic resistance and how to reduce it, distinguish medical and recreational drugs, and describe the effects of alcohol and tobacco on health.
How antibiotics work
Antibiotic resistance
Medical and recreational drugs
A drug is a substance that changes how the body works. Medical drugs are used to treat illness (such as antibiotics and painkillers). Recreational drugs are taken for their effects and can be legal (such as alcohol and tobacco) or illegal; many are addictive and harm health.
Effects of alcohol and tobacco
Alcohol is a depressant that slows reactions; heavy use damages the liver (cirrhosis) and the brain. Tobacco smoke damages the lungs (causing bronchitis, emphysema and lung cancer) and the circulation; carbon monoxide in the smoke reduces the oxygen the blood can carry.
Examples in context
Example 1. Why MRSA is a problem in hospitals. MRSA is a strain of bacteria that has become resistant to many antibiotics through natural selection, partly because antibiotics have been so widely used. In hospitals, where many vulnerable patients are close together, a resistant infection is hard to treat and can spread. This is why hospitals stress hand washing and careful antibiotic use. MRSA is a real example of antibiotic resistance, linking this topic directly to natural selection.
Example 2. Why a cold should not be treated with antibiotics. A cold is caused by a virus, so an antibiotic cannot cure it; the body's own immune system clears the virus. Taking an antibiotic anyway gives no benefit and exposes the bacteria living harmlessly in the body to the drug, selecting for resistant ones. Over a whole population, this needless use makes resistance spread faster. This is why doctors increasingly refuse antibiotics for viral illnesses, a point CCEA expects you to explain using both biology and the idea of resistance.
Try this
Q1. Why do antibiotics not work against a cold? [1 mark]
- Cue. A cold is caused by a virus, and antibiotics only kill bacteria.
Q2. Give one way to reduce antibiotic resistance. [1 mark]
- Cue. Only use antibiotics when needed (or always finish the full course).
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 20204 marksExplain why antibiotics cannot be used to treat a viral infection such as a cold.Show worked answer →
Four marks for what antibiotics do and why viruses are different.
Antibiotics work by killing bacteria or stopping them reproducing, for example by damaging their cell walls.
Viruses do not have the same structures as bacteria and reproduce inside the body's own cells.
So antibiotics have no effect on viruses, and taking them for a cold will not help.
Overusing antibiotics for viral infections also wastes them and increases the risk of antibiotic resistance developing in bacteria.
Markers reward antibiotics killing bacteria, viruses being different and hiding inside cells, antibiotics not affecting viruses, and the resistance point.
CCEA 20194 marksDescribe how antibiotic resistance can be reduced.Show worked answer →
Four marks for sensible measures with reasons.
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 that even the more resistant bacteria are killed and cannot reproduce.
Antibiotics should not be overused in farming.
New antibiotics can be developed, though this is slow.
Markers reward not over-prescribing, finishing the course, reducing use in farming, and the link to slowing the spread of resistant bacteria.
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Sources & how we know this
- CCEA GCSE Biology specification — CCEA (2017)