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?
What colour are Gram Negative bacteria after staining?
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