Drugs and antibiotics
What a drug is
- A drug is any substance taken into the body that changes its chemical reactions.
- Many drugs are medicines that treat illness.
- "Drug" means any such substance — not only illegal ones.
Practice
A drug is:
A drug is any substance taken into the body that changes its chemical reactions — many are helpful medicines.
Antibiotics
- Antibiotics treat bacterial infections — they kill bacteria or stop them growing.
- They do not affect viruses, so they can't cure a cold or flu.
- To test antibiotics: discs soaked in different ones are placed on a plate of bacteria — a clear ring shows where bacteria were killed (a bigger ring = more effective).
Practice
Antibiotics work against:
Antibiotics kill bacteria or stop them growing; they have no effect on viruses, so they can't cure a cold or flu.
Antibiotic resistance
- Some bacteria are resistant — the antibiotic no longer kills them.
- These survive and multiply, so the antibiotic becomes less effective for everyone.
- (Supplement) To slow it: use antibiotics only when needed and always finish the course. Overuse spreads resistant bacteria like MRSA.
Practice
Overusing antibiotics leads to resistant bacteria such as MRSA.
Overuse lets resistant bacteria survive and multiply; using antibiotics only when needed and finishing the course slows this.
You've got it
Key idea
- a drug = any substance that changes the body's chemical reactions (not only illegal ones)
- antibiotics kill bacteria only — useless against viruses (colds, flu)
- overuse → resistant bacteria (e.g. MRSA); use only when needed and finish the course