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Flashcards in Session 3 - incomplete Deck (14):

Define limit of resolution

- The minimum distance at which two objects can be seen as distinct


Why are electron microscopes capable of finer resolution than light microscopes?

- Limit of resolution is proportional to wavelength (ie resolution improves as wavelength decreases)
- Electrons have a smaller wavelength than visible light
- Theoretical limit of resolution: light = 0.2um; electron = 0.002nm


What is infection?

- The multiplication/colonisation of a pathogenic microbe on/in a susceptible host with associated distinction/damage


What causes infection?

- Pathogenic microbes (meet the Henle-Koch postulates)


Why do particular individuals get particular infections?

- Different individuals are susceptible to particular infections due to:
~ weakened immune systems
~ poor nutrition
~ poor living circumstances
~ no access to health care eg vaccinations
~ genetic predisposition
~ lifestyle eg STDs


What influences the outcome of infection?

- Host's immune system
- Affected body systems
- Drugs used


What is significant about the gram stain?

- Can detect and classify most bacteria
- Can be classified as gram positive or negative depending on its cell wall


What colour are Gram Positive bacteria after staining?

- Blue


What colour are Gram Negative bacteria after staining?

- Red


What is the overview of the gram staining process?

- Crystal violet -> Iodine -> Acetone/Methanol -> Red dye


What is the gram staining process?

1) Positively charged CRYSTAL VIOLET binds to negatively charged cell contents
2) IODINE forms a large molecular complex with Crystal Violet
3) ACETONE or METHANOL extract the complexes through the Gram-negative cell wall but not through the Gram-positive cell wall
4) A RED DYE is used to stain the Gram negative cell walls


What is the significance of the Acid Fast Stain?

- Allows the detection of mycobacterium eg tuberculosis and leprosy
- I.e. Bacteria that cannot be identified by gram staining


Define a pathogen

- A bacterium, virus or other microorganism that can cause disease


Define a non-pathogen

- A bacterium that doesn't cause disease
- Many non-pathogens perform essential ecological roles