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Flashcards in lecture 1.2 Deck (39):
1

What is the highest practical magnification of a light microscope?

about 1000-1500

2

What is the highest practical magnification of a transmission electron microscope?

over 100,000

3

What is the best resolution of a light microscope?

0.2 um

4

What is the best resolution of a transmission electron microscope?

0.5 um

5

What is the radiation source for a light microscope?

visible light

6

What is the radiation source for a transmission electron microscope?

electron beam

7

What is the medium of travel for a light microscope?

air

8

What is the medium of travel for a transmission electron microscope

high vaccum

9

What is the type of lens for a light microscope?

glass

10

What is the type of lens for a transmission electron microscope?

electronmagnet

11

What is the source of contrast in a light microscope?

different light absorptions

12

What is the source of contrast in a transmission electron microscope?

scattering of electrons

13

What is the focusing mechanism of a light microscope?

adjust the lens position mechanically

14

What is the focusing mechanism of a transmission electron microscope?

adjusts current to magnetic lens

15

What is the method of changing magnification in a ligh microscope?

switch the objective lens or eyepeice

16

What is the method of changing madnification in a transmission electron microscope?

adjust to the current magnetic lens

17

How is the specimen mounted in a light microscope?

on a glass slide

18

How is the specimen mounted in a transmission electron microscope?

on a metal grid, usually copper

19

What are the types of light microscopes?

bright-field microscope
dark-field microscope
phase-contrast microscope
fluorescence microscope

20

How are the images formed?

image formed by action of 2 lenses, are compound microscopes

21

What defines the Phase-Contrast microscope?

excellent way to observe living cells
enhances the contrast between intracellular structures

22

What is a good example of a Phase- Contrast microscope?

Especially useful for detecting bacterial components such as endospores and inclusion bodies that have refractive indices different from that of water

23

How does a Phase-Contrast microscope create an image?

Some light rays from hollow cone of light passing through unstained cell slowed/out of phase (dark against bright background)
Converts differences in refractive index/cell density into detected variations in light intensity

24

How does the Differential Interference Contrast Microscope (DIC) create an image?

creates image by detecting differences in refractive indices and thickness of different parts of specimen

25

What is the Differential Interference Contrast Microscope (DIC) used for?

excellent way to observe living cells. Live, unstained cells appear brightly colored and three-dimensional

26

What is the radiation source for a fluorescence microscope?

ultraviolet, violet, or blue light

27

In a fluroscence microscope, what is the specimen stained with?

Fluorochromes

28

How does a Fluorescence microscope create an image?

shows a bright image of the object resulting from the fluorescent light emitted by the specimen

29

What is a fluorochrome?

fluorochrome-labeled probes, such as antibodies, or fluorochrome dyes tag specific cell constituents for identification of unknown pathogens
can be used to localize specific proteins in cells

30

What is red/green dye?

Live cells are stained green where as dead cells are stained red

31

What is the light source for a Confocal Microscope?

laser beam

32

How does a Confocal Microscope create an image?

creates sharp, composite 3D image of specimens by using laser beam, aperture to eliminate stray light, and computer interface

33

How does a Scanning Electron Microscope create an image?

uses electrons reflected from the surface of a specimen to create image
produces a 3-dimensional image of specimen’s surface features

34

How does electron cryotomography work?

The speciem goes through rapid freezing and the images are recorded from many different directions to create 3-D structures

35

What does rapid freezing show?

cytoskeletal elements, magnetosomes, inclusion bodies, flagellar motors, viral structures

36

What is the radiation source for 3-D EM tomography?

electron beam

37

How does 3-D EM Tomography create an image?

Images are collected by tilting the specimen in the electron beam and collecting images at 1-2º intervals. Superimposition of image detail is resolved by computing 3-D reconstruction via back-projection algorithms

38

How does a scanning tunneling microscope work/create an image

steady current (tunneling current) maintained between microscope probe and specimen
Up/down movement of probe as it maintains current is detected, used to create image of surface of specimen

39

How much can a scanning tunnelting microscope magnify?

Magnification 100 million times, can view atoms on surface of a solid