Bacterial diseases (AQA GCSE Biology Combined Science): Revision Notes
Bacterial diseases
What are bacteria?
Bacteria are tiny living things called prokaryotic organisms. This means they don't have a proper nucleus like our cells do. Some bacteria can act as pathogens - organisms that cause disease.
The key difference between prokaryotic and eukaryotic cells is that prokaryotic cells (like bacteria) have their DNA freely floating in the cytoplasm, while eukaryotic cells (like human cells) have their DNA enclosed within a membrane-bound nucleus.
Basic structure of a bacterial cell:
- Contains cytoplasm (jelly-like substance inside the cell)
- Has a loop of DNA (genetic material)
- May have plasmids (small rings of extra DNA)
- Surrounded by a cell membrane
- Protected by a cell wall on the outside
Key features of bacteria
Bacteria have several important characteristics that make them effective at causing disease:
- Size: Usually smaller than plant and animal cells, but bigger than viruses
- Reproduction: Can multiply very quickly inside your body
- Harmful effects: Some produce toxins (poisons) that damage your tissues and make you feel ill
- What they infect: Can cause disease in both plants and animals
- How they spread: Through direct contact between people, contaminated water, or through the air
Bacteria can reproduce incredibly fast - some types can double their numbers every 20 minutes under the right conditions. This rapid reproduction is why bacterial infections can become serious quickly if left untreated.
Common bacterial diseases include cholera and tuberculosis (TB).
Human bacterial diseases
Understanding specific bacterial diseases helps us recognise symptoms and know when to seek treatment.
Salmonella food poisoning
Disease Example: Salmonella Food Poisoning
How it spreads:
- Eating food that contains salmonella bacteria
- Bacteria get into food when it's prepared in dirty conditions
Symptoms you get:
- Fever (high temperature)
- Stomach cramps and pain
- Vomiting (being sick)
- Diarrhoea (runny poo)
Gonorrhoea
Disease Example: Gonorrhoea
How it spreads:
- Sexual contact between infected people
- This makes it a sexually transmitted infection (STI)
Symptoms you get:
- Thick yellow or green discharge from private parts
- Pain when urinating (peeing)
Treatment and prevention
Modern medicine has given us powerful tools to fight bacterial infections, but we also face new challenges. Antibiotics can kill bacteria inside your body. However, many bacteria are now becoming resistant to antibiotics. This means the medicines don't work as well anymore, making bacterial infections harder to treat.
Antibiotic Resistance Crisis
The overuse and misuse of antibiotics has led to the development of "superbugs" - bacteria that are resistant to multiple antibiotics. This is one of the biggest threats to global health today, making previously treatable infections potentially deadly again.
Prevention methods:
- Wash your hands regularly, especially before handling food
- Cook food properly to kill harmful bacteria
- Use condoms during sexual activity to prevent STIs like gonorrhoea
Historical discovery
A doctor called Ignaz Semmelweis (1818-1865) made an important discovery about preventing bacterial infections. He noticed that fewer women died from infection when doctors washed their hands between patients. At the time, people didn't know about bacteria, so they couldn't understand why hand washing worked so well.
Semmelweis is now known as the "father of hand hygiene." His discovery that handwashing dramatically reduced deaths from childbed fever was initially rejected by the medical community, but his work laid the foundation for our modern understanding of infection control.
Remember!
Key Points to Remember:
- Bacteria are prokaryotic organisms that can cause disease
- They reproduce quickly and some produce harmful toxins
- Salmonella spreads through contaminated food and causes stomach problems
- Gonorrhoea spreads through sexual contact and causes discharge and pain
- Antibiotics can treat bacterial diseases, but resistance is becoming a problem
- Good hygiene (like hand washing) and safe practices help prevent bacterial infections