Test 1 - Introduction

Question 1

Resolution of the naked eye is

Answer 1

0.2 mm

Question 2

What was the first microscope like? Who was it invented by and what was its magnification and resolution? Were microorganisms visible?

Answer 2

Hooke; 30 x and 0.07 mmm; hence, microorganisms invisible (ex. E.coli is 0.02 mm)

Question 3

Microscope 2.0: who improved upon it? Why was it useful? Not useful?

Answer 3

Leeuwenhoek; microorganisms visible, but no germ theory yet. Hence, functionally useless.

Question 4

Who is responsible for the Germ Theory of Diseases? Which organisms did he use to illustrate which disease?

Answer 4

Koch; Bacillius anthracis for Anthrax and Mycobacerium tuberculosis for T.B.

Question 5

What were Koch’s Postulates? What did it prove? Give the steps.

Answer 5

Linked disease to specific microorganisms.

1. Microbe is seen in all cases of disease but absent in the healthy
2. Microbe is able to be isolated and cultured
3. Microbe causes sickness when introduced to healthy host.
4. Microbe is able to be isolated and cultured from the newly diseased host.

Question 6

What part of Koch’s Postulate is different with the advent of new technology?

Answer 6

Microbe was isolated and identified with use of microscopes until a decade ago, when genomics were used instead.

Question 7

What is resolution? What is contrast?

Answer 7

Resolution is the smallest distance 2 items can be separated and still seen to be 2 separate items. Contrast is the edge of something against background.

Question 8

What happens with items when no resolution and no contrast gives a large blurry mass?

1. no resolution with contrast,
2. resolution without contrast,
3. resolution with contrast

Answer 8

1. no resolution with contrast –> two different things seemingly stuck together
2. resolution without contrast –> two indistinguishable items near but separate from each other
3. resolution with contrast –> two different things near but separate from each other

Question 9

What is resolution based on? The gist of formula?

Answer 9

Wavelike nature of light; in low power lens, the light shining on the specimen is “thinner” while in high power lens, it is “thicker”. Hence, according to resolution = (0.61 x wavelength) / (refractive index x sin(thetha/ half angle)), “thicker” light that focus on the specimen gives higher resolution.

Question 10

Identify the lens as well as the direction of light and then describe the lens’ purpose.
( O ) <–Eyes
[…..]

(…..)
____
{…..}

Answer 10

( O ) <-Condenser

• Ocular: Focus light on eyes (10x)
• Objective: Collect light from specimen & magnifies image (∆Objective=∆thetha=∆resolving power)
• Condenser: Focus light on specimen
• Light moves from beneath and crosses at the condenser, focusing on specimen, and then reaches outward and straight to ocular, where it focuses on the eyes

Question 11

Contrast is increased with (1) and (2)

Answer 11

(1) Fixing and (2) Staining

Question 12

What is fixing?

Answer 12

Cross-linking cytoplasm to lock things in place internally and onto the slide, killing cell in progress.

Question 13

What are the 4 kinds of staining? Give examples of each.

Answer 13

1. Direct Staining: Stain bacteria and leave surrounding clear. (+) dye attracted to (-) bacterial surface. (ex. MB & CV)
2. Indirect Staining: Stain by leaving bacteria clear. (ex. Nigrosin)
3. Spore Staining: Stains only spores. (ex. Malchite)
4. Gram Staining: Staining based on ability of gram stain to stick to cell wall. (CV -> Mordant/Iodine (binds to CV and traps it in cell) -> Decolorization/Alcohol -> Counterstaining/Safranin)

Question 14

What is fluorescence?

Answer 14

Absorbing light at one wavelength and releasing it at another, lower wavelength. (Always lower because of energy lost.)