Pathogenic Microorganisms | OCR A-Level Biology B (Advancing Biology) (H422)
Pathogenic Microorganisms
- 86 questions
- 6 subtopics
- Biology content, examined on all three papers
- Component 01, Component 02 and Component 03
Pathogenic Microorganisms is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper.
It covers how pathogens cause communicable disease, tuberculosis, HIV, AIDS and the structure of the virus, identifying bacteria: Gram staining and culture, epidemiology: incidence, prevalence and mortality and notifiable diseases and the control of HIV and TB.
Sample questions from Pathogenic Microorganisms
Answer each one closed book first, then open the answer.
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How pathogens cause communicable disease
Distinguish between a bacterial exotoxin and an endotoxin.
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An exotoxin is a soluble protein actively secreted by a living bacterium, whereas an endotoxin is the lipopolysaccharide of the outer membrane of a Gram-negative cell and is released mainly when the cell dies and breaks apart. -
How pathogens cause communicable disease
How do fungi obtain nutrients from the tissue of their host?
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They secrete hydrolytic enzymes out of their hyphae to digest the host's tissue, then absorb the soluble products. -
Tuberculosis
What is a tubercle?
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A tubercle is a small mass of scar tissue and immune cells formed in the lung, which walls off and contains the bacteria. -
Tuberculosis
What is the standard drug treatment for active tuberculosis?
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A combination of antibiotics, typically isoniazid, rifampicin, pyrazinamide and ethambutol, is taken for six to nine months, with all four given for the first two months. -
HIV, AIDS and the structure of the virus
What is the function of the glycoprotein gp120 on the surface of HIV?
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It is the attachment protein, binding to the CD4 receptor on the surface of a T helper cell. -
HIV, AIDS and the structure of the virus
Why does the loss of T helper cells leave a person vulnerable to many different infections?
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T helper cells release the cytokines that activate B cells, T killer cells and phagocytes, so without them the specific immune response cannot be coordinated against any pathogen. -
Identifying bacteria: Gram staining and culture
Why do Gram-negative bacteria lose the crystal violet stain?
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The alcohol dissolves their outer lipopolysaccharide membrane and their peptidoglycan layer is thin, so the crystal violet–iodine complex washes out and the cells then take up the counterstain. -
Identifying bacteria: Gram staining and culture
State four features of a bacterial colony that are used to help identify the species.
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The diameter of the colony, its overall shape, whether its edge is smooth or irregular, and its colour.
The 6 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| How pathogens cause communicable disease | Recall questions on pathogens, communicable disease and virulence, how bacteria harm their hosts with exotoxins and endotoxins, the cholera toxin, viruses as obligate intracellular parasites, fungi that digest skin with keratinase in athlete's foot, and other causes of symptoms. | 13 |
| Tuberculosis | Recall questions on Mycobacterium tuberculosis and Mycobacterium bovis, droplet transmission, survival inside macrophages, tubercles, primary and dormant infection, the triggers and symptoms of active secondary tuberculosis, combination antibiotic treatment and directly observed treatment. | 14 |
| HIV, AIDS and the structure of the virus | Recall questions on HIV as a retrovirus, its RNA, capsid, envelope and gp120, the roles of reverse transcriptase, integrase and protease, how HIV is transmitted, the loss of T helper cells, opportunistic infections and AIDS, and antiretroviral therapy. | 15 |
| Identifying bacteria: Gram staining and culture | Recall questions on the steps of Gram staining and why Gram-positive and Gram-negative bacteria differ in colour, iodine as a mordant, Staphylococcus aureus and Escherichia coli, acid-fast staining of Mycobacterium tuberculosis, cell shapes and colony features, streak plates and safe incubation. | 14 |
| Epidemiology: incidence, prevalence and mortality | Recall questions on incidence, prevalence, mortality and case fatality rates and how to calculate them, endemic disease, epidemics and pandemics with chickenpox, SARS and H1N1 as examples, and interpreting trends in HIV and tuberculosis data. | 17 |
| Notifiable diseases and the control of HIV and TB | Recall questions on notifiable diseases and why they are reported on suspicion, how notification data are used, Public Health England and the UK Health Security Agency, why HIV is not notifiable, and the biological, social, economic and ethical difficulties of controlling HIV and tuberculosis. | 13 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Biology B (Advancing Biology) Active Recall Guide
Every topic, not just this one. 2,895 questions with their answers.