2.2.15Reproduction and Inheritance
Antibiotic Resistance — Edexcel International GCSE Science Double Award (Modular) - Biology Unit 2 Revision Notes & Topical Questions
5 min read 10 parts Lesson 28 of 28
Section 1 of 10What antibiotics do
Target
- Target processes found in bacterial cells but not in human cells.
- Examples are blocking building of the cell wall or blocking protein synthesis.
Result
- Result the bacteria burst or cannot grow and divide.
Safety
- Safety the patient's own cells are not damaged.
Section 2 of 10Why viruses are not affected
Not cells
- Not cells viruses have no cell wall and no metabolism of their own.
Reproduction
- Reproduction they multiply inside host cells using the host machinery.
No target
- No target an antibiotic has nothing in the virus to attack.
Other control
- Other control viral infections are fought by the immune system, helped by antiviral drugs or prevented by vaccines.
Section 3 of 10Bacterium and virus compared
| Feature | Bacterium | Virus |
|---|---|---|
| Is it a cell | Yes, single cell | No: genetic material in a protein coat |
| Cell wall | Present | Absent |
| Own ribosomes and metabolism | Yes | No: uses the host cell |
| Reproduces | By itself, by dividing | Only inside host cells |
| Killed by antibiotics | Yes, unless resistant | No |
Section 4 of 10How a resistant strain develops
1
Bacteria reproduce very quickly, so random mutations arise often.
2
One mutation lets a bacterium survive a particular antibiotic.
3
When the antibiotic is used, non-resistant bacteria are killed.
4
Resistant bacteria survive, face less competition and reproduce.
5
They pass the resistance allele to their offspring.
6
Over many generations most of the population is resistant.
Section 5 of 10Natural selection model
1Variation
- Variation some bacteria carry a resistance allele.
2Selection pressure
- Selection pressure the antibiotic.
3Survival of the better adapted
- Survival of the better adapted resistant cells live.
4Inheritance
- Inheritance resistance is passed on.
Section 6 of 10MRSA
MRSA
MRSA a strain of a common skin bacterium resistant to several widely used antibiotics.
Hospitals
- Hospitals a serious problem there, because many antibiotics are used and patients are vulnerable.
Treatment
- Treatment infections are hard to treat because few drugs still work.
Section 7 of 10Limiting resistance
1
Use antibiotics only when essential, not for viral infections.
2
Complete the full course.
3
Do not share or save leftover antibiotics.
4
Limit antibiotic use in farming, especially to make animals grow faster.
5
Keep hospitals hygienic with hand washing and cleaning.
Section 8 of 10More from the specification
Disease
- A condition in which part of the body does not function properly.
Incidence
- Number of new cases in a period per population.
Drug
- Drug any substance taken into the body that modifies or affects chemical reactions in the body.
Antibiotics
- Antibiotics medicinal drugs used to treat bacterial infections.
Liver
- Liver the main site of drug metabolism in the body.
Section 9 of 10Key terms
| Term | Meaning |
|---|---|
| Antibiotic | A drug that kills bacteria or stops their growth without harming human cells. |
| Resistance | The ability of bacteria to survive an antibiotic. |
| Mutation | A random change in genetic material. |
| Selection pressure | A factor, such as an antibiotic, that favours survival of some individuals. |
| MRSA | A bacterium resistant to several widely used antibiotics. |
| Allele | A version of a gene. |
Section 10 of 10Exam technique
1
Saying antibiotics work on viruses — viruses are not cells and have no target.
2
Saying antibiotics make bacteria mutate — resistance mutations are random.
3
Saying a person becomes resistant — the bacteria become resistant.
4
Saying MRSA is a virus — it is a bacterium.
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