Antibiotics and painkillers (AQA GCSE Biology): Revision Notes
Antibiotics and painkillers
What are painkillers?
Painkillers are medicines that help you feel better when you're ill. They treat the symptoms of a disease. Symptoms are things like headaches, fever, and body aches that make you feel unwell.
Critical Understanding: Painkillers do not kill the germs (pathogens) that cause the disease. They just help you feel more comfortable while your body fights the infection.
What are antibiotics?
An antibiotic is a medicine that kills bacteria inside your body. Unlike painkillers, antibiotics actually attack and destroy the germs causing bacterial diseases.
Key facts about antibiotics:
- They only work against bacterial infections
- Different bacteria need different antibiotics
- Doctors must choose the right antibiotic for each infection
- They have saved millions of lives by curing bacterial diseases
- Penicillin was one of the first antibiotics discovered
The discovery of antibiotics revolutionised medicine in the 20th century. Before antibiotics, many bacterial infections that we can easily treat today were often fatal.
How do antibiotics work?
Antibiotics target bacteria in specific ways. For example, some antibiotics stop bacteria from building their cell walls properly. This kills the bacteria but doesn't harm human cells because our cells don't have cell walls.
This is why antibiotics can kill bacteria without damaging your body's tissues.
How Selective Targeting Works: The key to antibiotic effectiveness is that they target structures or processes that exist in bacteria but not in human cells. This selective targeting is what makes antibiotics both effective and relatively safe.
Antibiotic resistance
Some bacteria have developed resistance to antibiotics. This means certain antibiotics can no longer kill them.
MRSA is a dangerous example. It's a type of bacteria that has become resistant to several different antibiotics.
How resistance develops:
- Mutation - Some bacteria change and become resistant to an antibiotic
- Survival - When the antibiotic is used, non-resistant bacteria die but resistant ones survive
- Reproduction - The resistant bacteria multiply and spread
- Population growth - Soon, most bacteria in that area are resistant
This process is called natural selection. If there's no new antibiotic to control the infection, it can spread quickly and cause serious outbreaks.
Growing Threat: Antibiotic resistance is one of the biggest threats to global health today. It can make common infections dangerous again and medical procedures much riskier.
Why antibiotics don't work on viruses
Viruses are completely different from bacteria. They live inside your body's cells and use those cells to make copies of themselves.
Key problems:
- Antibiotics cannot kill viruses
- Drugs that kill viruses often damage human cells too
- This makes it very difficult to develop safe antiviral medicines
This is why there are few treatments for viral diseases like colds and flu. Your body's immune system has to fight off most viral infections on its own.
Common Misconception: Many people ask for antibiotics when they have viral infections like colds or flu. This is not only ineffective but can also contribute to antibiotic resistance by encouraging unnecessary antibiotic use.
Key Points to Remember:
- Painkillers treat symptoms but don't kill germs
- Antibiotics kill bacteria but not viruses
- Different bacterial infections need different antibiotics
- Antibiotic resistance happens when bacteria evolve to survive antibiotic treatment
- MRSA is a dangerous resistant bacteria
- Antiviral drugs are hard to develop because they often harm human cells too