Pathogenic Microorganisms

What Pathogenic Microorganisms covers

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.

The 6 subtopics

Each one has its own page.

• How pathogens cause communicable diseaseRecall 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.Open →
• TuberculosisRecall 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.Open →
• HIV, AIDS and the structure of the virusRecall 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.Open →
• Identifying bacteria: Gram staining and cultureRecall 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.Open →
• Epidemiology: incidence, prevalence and mortalityRecall 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.Open →
• Notifiable diseases and the control of HIV and TBRecall 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.Open →

What you need to know

Answer each one before you reveal it.

Take Pathogenic Microorganisms further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Epidemic vs Pandemic

  Epidemic: a sharp rise in the number of cases of a disease within one population or region over a short period. Pandemic: an outbreak that has spread across several countries or continents, as H1N1 influenza did in 2009.

• Primary TB vs Secondary TB

  Primary TB: the first infection, in which the bacteria are usually walled off inside the lungs and cause few or no symptoms. Secondary TB: reactivation of bacteria that have lain dormant for years, once immunity falls, giving the destructive lung disease.

• HIV vs AIDS

  HIV: the retrovirus that infects T helper cells, and the infection it causes, which can persist for years with no symptoms. AIDS: the late stage reached once T helper cell numbers have fallen so far that opportunistic infections and rare cancers take hold.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is a pathogen?

   Model answer

   A pathogen is a microorganism or virus that invades a host and causes disease.

2. 2

   What makes a disease communicable?

   Model answer

   A communicable disease is caused by a pathogen and can be passed from one infected organism to another.

3. 3

   Define the term virulence.

   Model answer

   Virulence is the degree to which a pathogen is able to cause disease in its host.

4. 4

   State the two general ways in which a bacterium harms the host it has infected.

   Model answer

   It releases toxins that damage or disrupt host cells, and it damages tissue directly as it multiplies within it.

5. 5

   Distinguish between a bacterial exotoxin and an endotoxin.

   Model answer

   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.

6. 6

   How does the toxin released by the cholera bacterium cause severe diarrhoea?

   Model answer

   It causes the epithelial cells lining the intestine to pump chloride ions into the gut lumen, so water follows by osmosis and is lost as watery faeces.

What is inside Levo

Six ways to work the same material.

Pathogenic Microorganisms revision questions

What does Pathogenic Microorganisms cover in OCR A-Level Biology B?

6 subtopics: 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. Each one has its own page with questions and model answers.

How is Pathogenic Microorganisms organised?

By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.