Session 3 - incomplete

Question 0

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

Answer 0

• 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

Question 1

Define limit of resolution

Answer 1

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

Question 2

What is infection?

Answer 2

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

Question 3

What causes infection?

Answer 3

• Pathogenic microbes (meet the Henle-Koch postulates)

Question 4

Why do particular individuals get particular infections?

Answer 4

• 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

Question 5

What influences the outcome of infection?

Answer 5

• Host’s immune system
• Affected body systems
• Drugs used

Question 6

What is significant about the gram stain?

Answer 6

• Can detect and classify most bacteria

- Can be classified as gram positive or negative depending on its cell wall

Question 7

What colour are Gram Positive bacteria after staining?

Answer 7

• Blue

Question 8

What colour are Gram Negative bacteria after staining?

Answer 8

• Red

Question 9

What is the overview of the gram staining process?

Answer 9

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

Question 10

What is the gram staining process?

Answer 10

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

Question 11

What is the significance of the Acid Fast Stain?

Answer 11

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

Question 12

Define a pathogen

Answer 12

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

Question 13

Define a non-pathogen

Answer 13

• A bacterium that doesn’t cause disease

- Many non-pathogens perform essential ecological roles