Lecture 2 - Observing the Microbial Cell

Question 1

We can see ___ with the naked eye but a less than ___ we need a microscope

Answer 1

• Eukaryotes

- .1 mm

Question 2

Describe how resolution is different than detection

Answer 2

-Detection is just the ability to determine the presence of an object whereas resolution is the ability to distinguish 2 objects when closely together

Question 3

What are 4 different ways that light can interact with a specimen?

Answer 3

• Absorption ->The light does NOT pass through but rather traps the heat
• Reflection ->The light bounces OFF the specimen
• Refraction ->The light bends after passing through another substance
• Scattering ->The light goes in all different directions

Question 4

Magnification relies on ____ and ____.

Answer 4

• Refraction

- Creating a focal point

Question 5

What is empty magnification?

Answer 5

-It is when you go pass 500x and do NOT get any better resolution

Question 6

Why use oil immersion when using a bright field microscope?

Answer 6

-Reduces the amount of light that refracts because the oil has the same refractive index as glass. Which allows for you to see your specimen and NOT the glass

Question 7

I want to look at a specimen while it is moving in my water sample. What type of microscope could I use?

Answer 7

• Bright Field
• Dark Field
• Phase Contrast

Question 8

List to steps for preparing a wet mount

Answer 8

• Take a drop of sample

- Drop a cover slip on

Question 9

How is Fluorescence Microscope different than Super-Resolution Imaging?

Answer 9

• Fluorescence; the specimen absorbs light at one wavelength and emits it at a lower wavelength
• Super-Resolution Imaging; breaks the diffraction of light

Question 10

Why would I use a Dark field microscope instead of a light microscope?

Answer 10

-Because the specimen is too small, too clear or we want to see the flagella

Question 11

How does Phase Contrast work?

Answer 11

• It works by increasing the refractive index between the specimen and background
  - Specimen gets darker and the background gets lighter

Question 12

What does a Differential Interference Contrast give you?

a) True 3-D picture
b) Normal Image
c) Nothing
d) False 3-D picture

Answer 12

D

Question 13

What is the difference between TEM and SEM?

Answer 13

• TEM shows the internal structures of a cell and produces an image by slicing
• SEM shows the surface of a cell

Question 14

True or False. Using Atomic Force Microscope the specimen is alive.

Answer 14

True

Question 15

What is the special step in creating a slide for cryo-electron microscopy?

Answer 15

-You have to flash-freeze the sample

Question 16

True or False. The sample is alive while looking at it

Answer 16

False, the sample is vaporized after the electrons hit it

Question 17

How many different stains can you put on a sample at once?

Answer 17

As may as you would like

Question 18

What is a sample stain?

Answer 18

• Colors ALL the cells one color to help give contrast from the background
• Methylene blue is a common example

Question 19

Why use a differential stain instead of a simple stain?

Answer 19

-Because you have only want to look at one type of cell

Question 20

Describe what an acid-fast stain works on

Answer 20

• Stains mycobacterium

- Carbolfuchsin is a common stain

Question 21

Describe a spore stain

Answer 21

• Detects spores

- Malachite green is a common stain

Question 22

What is the staining procedure for methylene blue?

Answer 22

-place a few drops and then wash with water

Question 23

What is the staining procedure for Gram staining?

Answer 23

-Place stain, add iodine, wash w/ ethanol and finally add safranin

Question 24

Why does Gram-positive stain purple?

Answer 24

-Because the thick cell wall and the negative charge present helps the stain stay in the cell wall