How to Revise Microbiology and Pathogens — Pearson A-Level Biology
Explain how pathogens cause disease. Describe the body's defence mechanisms
Examiner Tips for Microbiology and Pathogens
- Use diagrams to show pathogen entry and immune response.
- Link specific pathogens to diseases they cause.
- Remember that vaccines stimulate the immune system.
- When explaining growth, always relate to binary fission in bacteria and budding in yeast, and use precise terminology like generation time.
- For growth curves, label all four phases on a properly scaled graph and explain how factors like nutrient depletion and waste accumulation trigger transitions.
- In compare-and-contrast questions, use a structured table to directly juxtapose bacterial and fungal characteristics for clarity and conciseness.
Common Mistakes in Microbiology and Pathogens
- Confusing bacteria and viruses in terms of treatment.
- Thinking all pathogens are harmful (some are beneficial).
- Forgetting that fever is a defence mechanism.
- Confusing bacterial pili with flagella, incorrectly attributing motility to pili.
- Assuming all fungi are multicellular, thereby neglecting unicellular yeasts like Saccharomyces.
- Misinterpreting the exponential growth phase as linear rather than logarithmic increase.
Key Marking Points
- Explains how pathogens (bacteria, viruses, fungi) cause disease.
- Describes the body's first line of defence (skin, mucous membranes).
- Outlines the immune response including white blood cells and antibodies.
- Distinguishes between specific and non-specific defences.
- Award credit for accurately labeling a diagram of a bacterium, including capsule, cell wall, plasma membrane, cytoplasm, ribosomes, nucleoid, plasmid, and flagellum.
- Credit should be given for differentiating Gram-positive and Gram-negative bacteria based on peptidoglycan thickness and outer membrane presence.