Exam 1: Chapter 1

Question 1

light microscopy

Answer 1

Light diffracted through series of glass lenses to produce magnified image

Question 2

components of light microscopy/light path

Answer 2

1) condenser lens
2) specimen
3) objective lens
4) ocular lens
5) eye or viewing screen

Question 3

modern microscopes have lenses with higher

Answer 3

NA (numerical aperture (light gather ability)

Question 4

how do you calculate final magnification

Answer 4

ocular lens * objective lens

Question 5

how is higher resolution of light microscopy measured

Answer 5

measured in distance between two points that can be discriminated as distinct points

Question 6

how is magnification measured

Answer 6

measured in enlargement value

Question 7

which is better: light or electron microscopy

Answer 7

• electron microscopy has higher resolution

- accelerated e- has shorter wavelength than shortest light microscopy wavelength

Question 8

electron microscopy

Answer 8

• uses beam of electrons instead of beam of light
• increased resolution by reducing wavelength of electrons through acceleration (voltage applied)
• electromagnets used to focus electron beam in magnification (current applied)
• specimen coated with heavy metals to get better diffraction of electrons

Question 9

X-Ray diffraction

Answer 9

-gives even higher resolution (level of individual molecules) than electron microscopy
- x-rays diffracted form atoms in protein crystal onto radiation-sensitive plate-image used to calculate positions of individual atoms in protein or other molecule
Maximum resolution ~1 A (10^-10m) (10x higher than EM)

Question 10

specific molecule (actin) is visualized through

Answer 10

immunofluorescence microscopy using epifluorescence microscope

Question 11

uses single light wavelength that excites fluorescent label on specific molecule

Answer 11

epi-fluorescence microscope

Question 12

epi-fluorescence microscope: excitation filter

Answer 12

allows only light of excitation wavelength of probe to reach specimen

Question 13

epi-fluorescence microscope: barrier filter

Answer 13

allows only light of emission wavelength of probe to reach eyepiece

Question 14

how is specific protein recognized in epifluorescence microscopy

Answer 14

1. Fluorescence microscopy of in vitro labeled protein
2. immunofluorescence microscopy
3. GFP-tagging

Question 15

fluorescence microscopy of in vitro labeled protein

Answer 15

the specific protein is expressed in bacteria, purified, and covalently linked to fluorescent molecule in vitro (in test tube) before it is injected into a living cell;

fluorescently labeled actin injected into living cell

Question 16

immunofluorescence microscopy

Answer 16

use a fluorescently labeled antibody that recognizes the specific protein is used to indirectly label the protein in a fixed specimen.

Question 17

GFP-tagging

Answer 17

express the protein as a GFP-fusion protein in a living cell

Question 18

what are antibodies?

Answer 18

• proteins expressed by B (plasma) cells of vertebrate immune system
• bind “foreign molecules with high specificity in immune response
• cell biologist produce antibodies against specific molecules for use in immunostaning and other types of exp’s.

Question 19

human tractable model

Answer 19

human tissue culture - immortalized cells originally derived form human cancer tissues