CIE iGCSE Co-ordinated Sciences-B14. Drugs- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-B14. Drugs – Study Notes
CIE iGCSE Co-ordinated Sciences-B14. Drugs – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Describe a drug as any substance taken into the body that modifies or affects chemical reactions in the body
- Describe the use of antibiotics for the treatment of bacterial infections
- State that some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics
- State that antibiotics kill bacteria but do not affect viruses
Supplement
- Explain how using antibiotics only when essential can limit the development of resistant bacteria such as MRSA
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Drugs
📌 Definition
A drug is any substance taken into the body that modifies or affects chemical reactions in the body.
🌱 Key Points
- Can be natural or synthetic.
- Can affect the nervous system, metabolism, or other body processes.
- Some drugs are medicinal (help treat diseases), while others are recreational (used for pleasure, may cause harm).
📊 Examples
| Type | Example | Effect |
|---|---|---|
| Medicinal drug | Antibiotics (e.g. penicillin) | Kill bacteria, treat infections |
| Pain relief | Paracetamol | Reduces pain & fever |
| Recreational (legal) | Alcohol, nicotine | Affects brain/nervous system |
| Recreational (illegal) | Heroin, cocaine | Strong effects on nervous system, addictive |
⚡ Quick Recap
Drug = substance that changes body’s chemical reactions.
May be helpful (medicine) or harmful (abuse).
Acts on body chemistry → can change mood, behavior, or health.
Antibiotics and Bacterial Infections
📌 Introduction
- Antibiotics are drugs used to treat bacterial infections.
- They kill bacteria or stop them from reproducing.
- Discovered from natural microorganisms (e.g. penicillin from fungi).
🌱 How Antibiotics Work
- Bactericidal antibiotics → kill bacteria directly.
- Bacteriostatic antibiotics → stop bacterial growth and reproduction, allowing body’s immune system to remove them.
⚠️ Important: Antibiotics only work on bacteria, NOT on viruses (e.g. cold, flu, HIV).
📊 Examples
- Penicillin → damages bacterial cell walls.
- Tetracycline → stops protein synthesis in bacteria.
🧬 Antibiotic Resistanc
- Overuse or misuse of antibiotics → bacteria can develop resistant strains (e.g. MRSA).
- Resistant bacteria survive, reproduce, and spread.
- This makes some infections very difficult to treat.
📊 Summary Table
| Feature | Antibiotics |
|---|---|
| Target | Bacteria only (not viruses) |
| Action | Kill or stop bacterial growth |
| Example | Penicillin |
| Limitation | Resistance may develop |
⚡ Quick Recap
Antibiotics = bacteria fighters.
Do NOT work against viruses.
Misuse → resistance problem.
Example: Penicillin.
Antibiotic Resistance
📌 Statement
Some bacteria are resistant to antibiotics, which reduces the effectiveness of antibiotics.
🌱 Key Points
- Resistance means the antibiotic no longer kills the bacteria.
- Resistant bacteria survive treatment and reproduce, spreading resistance.
- Example: MRSA (Methicillin-resistant Staphylococcus aureus).
📊 Why It’s a Problem
- Infections become harder to treat.
- Stronger or multiple antibiotics may be needed.
- Can lead to untreatable “superbug” infections.
⚡ Quick Recap
Some bacteria resist antibiotics → treatment less effective.
Resistance spreads quickly.
Big medical concern worldwide.
Memory tip: “Resistant bacteria = antibiotics don’t work.”
Antibiotics: Effect on Microbes
📌 Statement
Antibiotics kill bacteria but do not affect viruses.
🌱 Key Points
- Bacteria → living cells with structures (like cell walls, ribosomes) that antibiotics can target.
- Viruses → not cells, they live inside host cells and use the host’s machinery to reproduce → antibiotics cannot reach or attack them.
- That’s why antibiotics treat bacterial infections (e.g. pneumonia, tuberculosis) but not viral infections (e.g. colds, flu, HIV).
📊 Summary Table
| Microbe | Effect of antibiotics |
|---|---|
| Bacteria | Killed / growth inhibited |
| Viruses | No effect |
⚡ Quick Recap
Antibiotics = bacteria killers only.
Viruses hide inside host cells → antibiotics useless.
Viral infections need vaccines or antiviral drugs, not antibiotics.
Memory tip: “AB = Against Bacteria, not Viruses.”
Limiting Antibiotic Resistance (e.g. MRSA)
📌 Introduction
Overuse or misuse of antibiotics encourages the spread of resistant bacteria like MRSA (Methicillin-resistant Staphylococcus aureus).
Using antibiotics only when essential helps slow this problem.
🌱 How Limiting Use Helps
- Less exposure = less chance of mutation
The fewer times bacteria are exposed to antibiotics, the fewer chances they have to develop resistant mutations. - Fewer resistant survivors
When antibiotics are overused, normal bacteria die but resistant ones survive and multiply. Restricting use reduces this selection pressure. - Preserves antibiotic effectiveness
Essential use only → keeps antibiotics working for serious infections.
📊 Example: MRSA
- MRSA is resistant to many common antibiotics.
- Spread in hospitals where antibiotics are heavily used.
- Controlled by:
- Careful prescription of antibiotics.
- Good hygiene to prevent spread.
⚡ Quick Recap
Overuse → resistance → “superbugs”.
Essential use only → slows resistance.
MRSA = classic example.
Memory tip: “Use less, protect more.”