Lecture 5

Question 1

Steam Sterilizing: Autoclave

Answer 1

• some contaminant organisms may survive 100˚C
• boiling point increased by pressure
• high boiling point = hotter steam
• at 15 PSI steam from boiling water is 121˚C

Question 2

Filtration of Heat-Labile Compounds

Answer 2

• liquids can be passed through filters which contain holes too small for bacteria to pass
• commonly 0.2µm pore size
• useful for solutions that can’t be heated

Question 3

Solutions that Can’t be Heated

Answer 3

• heat will sterilize it
• Ammonium Acetate
• Penicilin
• IPTG (a lactose analog)

Question 4

Basic Microscopy

Answer 4

• used to visualize objects down to ~0.2µm
• 2 lenses in combo can magnify an object 2000x
• ocular and objective lenses

Question 5

Ocular Lense

Answer 5

• making image bigger but not sharper

- empty magnification

Question 6

Objective Lense

Answer 6

• 4x, 10x, 40x, 100x

Question 7

Quality of Image Depends on:

Answer 7

1. thickness of section
2. lighting
3. quality/cleanliness of lenses
4. staining

Question 8

Eyepiece

Answer 8

• a magnifying lens, usually about 10x

Question 9

Condenser

Answer 9

• focuses the light

Question 10

Iris Diaphragm

Answer 10

• controls the amount of light that enter the objective lens

Question 11

Objective Lens

Answer 11

• # of lenses that provide different magnifications

- the total magnification is the product of the magnification of the eyepiece lens and the objective lenses

Question 12

How to Focus a Microscope

Answer 12

1. turn on light, open diaphragm, raise condenser
2. select lowest power objective lens
3. place slide on stage, use clips/arm
4. raise stage to highest or lowest position
5. position slide so something is under lens
6. use both eyes, adjust eyepieces
7. lower slide until object seen
8. wiggle slide if must
9. select next objective, use ONLY fine focus to adjust microscope

Question 13

Magnification

Answer 13

• how big something looks

Question 14

Empty Magnification

Answer 14

• a bigger image is useless without more detail

Question 15

Resolution

Answer 15

• something that is measured, can be calculated
• increases detail of image
• the smallest resolvable distance between 2 objects

Question 16

Resolution Equation

Answer 16

R = 0.61(wavelength)/NA

Question 17

Numerical Aperture Equation

Answer 17

NA = nsin(pheta)

- n: the refractive index of the material the light travels through from subject to lens

Question 18

Oil Immersion

Answer 18

• light can pass straight through entire interface
• same refractive index as glass of lens
• only the 100x should be used with oil

Question 19

Resolution and Field of View

Answer 19

• increase in Resolution = decrease in field of view