How Antibiotics Work and Their Limitations Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Learn how antibiotics like penicillin kill bacterial infections, why specific antibiotics target specific bacteria, and understand why antibiotics canno...

• Explain how antibiotics work to kill bacterial pathogens inside the body
• Describe why specific antibiotics must be used to treat specific bacterial infections
• Evaluate the benefits and limitations of antibiotic use in treating disease
• Explain why antibiotics cannot kill viral pathogens

Key ideas to keep in view

Use this lesson to stay inside B6.3 Monitoring and maintaining health while connecting the detail back to the wider B6: Global challenges topic.

• B6: Global challenges
• B6.3 Monitoring and maintaining health
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from How Antibiotics Work and Their Limitations before testing yourself from memory.

• Before 1928, a simple cut could kill you. Bacterial infections like pneumonia, tuberculosis and sepsis were death sentences. Then Alexander Fleming discovered penicillin by accident - a mould that killed bacteria in his petri dish. This discovery launched the antibiotic age and saved millions of lives.
• But here's the problem: bacteria are fighting back. Some infections that were once easily cured are becoming untreatable again. We're in an arms race with microscopic enemies that evolve faster than we can develop new weapons.
• A medicine that kills or inhibits the growth of bacteria inside the body by targeting specific bacterial structures or processes.
• Antibiotics are like molecular assassins - they target bacteria with surgical precision. Different antibiotics attack bacteria in different ways. Some destroy the bacterial cell wall, causing the cell to burst. Others interfere with protein synthesis, stopping bacteria from making essential proteins they need to sur...
• The key is specificity. Antibiotics target structures or processes that exist in bacterial cells but not in human cells. This is why they can kill bacteria without harming us - most of the time.
• Trap: Many students think antibiotics 'boost your immune system'. Actually, antibiotics directly kill bacteria - your immune system does the cleanup afterwards.
• Not all antibiotics work against all bacteria. This is crucial for exam success: specific bacteria must be treated with specific antibiotics. It's like having different keys for different locks.
• Bacteria have different cell wall structures, different enzymes, and different vulnerabilities. Penicillin works brilliantly against Streptococcus (causing strep throat) but is useless against Mycobacterium tuberculosis (causing TB). That's why doctors need to identify the specific bacterial species before prescribi...
• This is why taking leftover antibiotics for a new infection is dangerous - you might be using the wrong weapon entirely.
• Here's a fact that catches many students out: antibiotics cannot kill viral pathogens. This isn't because antibiotics are weak - it's because viruses are fundamentally different from bacteria.

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.