Microscopy

Question 1

What can you see under a microscope?

Answer 1

• unicellular organisms
• individual cells in a multicellular organism
> how structure relate to their function

Question 2

What are the two lenses in a compound light microscope?

Answer 2

• objective lens(near specimen)

* eyepiece lens(through which specimen is viewed)

Question 3

What is the job of the objective lens?

Answer 3

• produces magnified picture

* eyepiece magnifies it again

Question 4

How does the compound microscope have a higher magnification than a simple microscope?

Answer 4

• configuration allows for much higher magnification and reduced chromatic aberration than in simple microscope

Question 5

How is illumination provided in a compound light microscope?

Answer 5

• by light underneath sample

* opaque specimens are illuminated from above

Question 6

How is a wet mount prepared?

Answer 6

• specimens are suspended in a liquid(water or oil immersion)
• cover slip on top

Question 7

How is a dry mount prepared?

Answer 7

• whole/ thinly sliced specimens placed onto centre of slide
• cover slip on top

Question 8

How is a squash slide prepared?

Answer 8

• first wet mount
• use lens tissue to gently press down cover slip
• squash sample between 2 slide to prevent damage(need care)

Question 9

How is a smear slide prepared?

Answer 9

• edge of a slide used to smear sample, creating thin, even coating on another slide
• cover slip on top

Question 10

How to prepare a gram stain

Answer 10

1. Add crystal violet on bacterial specimen
2. Add iodine to fix the dye
3. Wash with alcohol-gram-ve lose stain(thinner walls), gram+ve retain blue-purple stain
   COUNTERSTAIN
4. Gram-ve are dyed by safranin getting a red colour

Question 11

How to prepare a slide?

Answer 11

1. Place sample on slide to air dry

2. Heat-fix by passing through flame(specimen adheres to slid and take up stain)

Question 12

How does +ve and -ve dyes dye cells?

Answer 12

• +ve are attracted to the -ve charged materials in cytoplasm leading to staining of cell components
• -ve repel -ve cytosol, dying outside of cell, creating a stained background(Negative stain technique)

Question 13

How to prepare acid-fast

Answer 13

• Lipid solvent used to carry carbolfuchsin dye into mycobacterium
• wash with dilute acid-alcohol solution > not affecting red stain
• other bacteria lose stained and are stained by methylene blue

Question 14

How do you produce a slide?

Answer 14

1. Fixing(chemicals preserve specimens in near natural state)
2. Sectioning(alcohol dehydrated specimens in mould with wax/resin are thinly sliced with microtome)
3. Staining
4. Mounting( cover slip)