Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

15.1Drugs

Drugs — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 10 parts Lesson 2 of 3 1 quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
0%read
Lesson summary

15.1 Drugs — IGCSE BIOLOGY notes: Define a drug and describe the use of antibiotics, why they do not affect viruses, and how resistant bacteria such as MRSA arise and are limited.Drug = any substance taken into the body that modifies or affects chemical reactions in the body.Medi…

  • Medicinal drug
  • Stopping early
  • Rapid reproduction
  • Resistant infections
  • Percentage killed
  • Antibiotic resistance

Part 1 of 8Drugs

Drug
Drug any substance taken into the body that modifies or affects chemical reactions in the body.
Medicinal drug
  • Medicinal drug a drug used to treat or prevent disease or relieve symptoms, such as antibiotics and painkillers.

Part 2 of 8Antibiotics

Antibiotics
  • Antibiotics used to treat bacterial infections.
  • They kill bacteria or stop their growth.
  • They act on structures and processes found only in bacterial cells, not human cells.
Viruses
  • Viruses antibiotics do not affect them.
  • Viruses have no cell wall or metabolism of their own and reproduce inside host cells.
  • There is no bacterial structure for the antibiotic to attack.

Part 3 of 8Bacteria and viruses compared

FeatureBacteriaViruses
CellularYes: cell wall, ribosomes, own metabolismNo: use host cell machinery
Antibiotic targets presentYesNo
Treated with antibioticsYesNo

Part 4 of 8Development of antibiotic resistance

1
A population of bacteria varies, and a random mutation makes one bacterium resistant.
2
The antibiotic is used and susceptible bacteria are killed.
3
The resistant bacterium survives because it is better adapted.
4
It reproduces rapidly by binary fission and passes on the resistance allele.
5
The resistant strain becomes more common.
6
The antibiotic no longer works against this strain, for example MRSA.

Part 5 of 8Why overuse increases resistance

Overuse
  • Overuse for viral infections or in livestock increases the chance that resistant strains are selected.
Stopping early
  • Stopping early a course stopped early may leave the more resistant bacteria alive to multiply.
Rapid reproduction
  • Rapid reproduction bacteria reproduce so fast that resistance spreads quickly through a population.
Resistant infections
  • Resistant infections are harder to treat and may need different or stronger antibiotics.

Part 6 of 8Minimising resistance

Minimising resistance
Use antibiotics only when essential.
Complete the full course so all bacteria, including less susceptible ones, are killed.

Part 7 of 8Percentage of bacteria killed

  • Percentage killed (initial number − final number) ÷ initial number × 100.

Part 8 of 8More from the specification

  • Incidence
    • Number of new cases in a period per population.

Key terms

TermMeaning
DrugA substance that modifies or affects chemical reactions in the body.
AntibioticA drug that kills bacteria or stops their growth and does not affect viruses.
Antibiotic resistanceThe ability of bacteria to survive an antibiotic, arising by mutation and spreading by natural selection.
MRSAMethicillin-resistant Staphylococcus aureus, a bacterium resistant to many antibiotics.
MutationA random change in genetic material.
PathogenA disease-causing organism.

Avoid these mistakes

1
Saying antibiotics treat colds and flu — these are viral infections.
2
Saying antibiotics cause resistance mutations — the mutations are random and the antibiotic selects them.
3
Saying people become resistant — the bacteria do.
4
Stopping the course when feeling better — the full course must be finished.

Last updated: