exam 1 visualizing cells Flashcards

1
Q

what are model eukaryotes (+ 4 features of them)

A

model organisms in which

  • the genome has been sequenced
  • site-directed and tissue specific mutagenesis is possible
  • expression of multiple genes can be tracked across many cells simultaneously
  • the developmental sequence is known
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the main issue with light microscopy

A

resolution is limited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the issue with electron microscopy

A

it requires special preservation and staining techniques

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what does light microscopy image

A

large-scale cellular structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what, in light microscopy, provides contrast and sensitivity

A

chemical stains and fluorescent molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

which form of microscopy has a higher resolution than light microscopy

A

electron microscopy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how does flow cytometry work

A
  • uses fluorescent labels to measure levels of biomolecules and ions
  • sorts cells into different tubes based on expression levels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is Cell Theory and who proposed it

A

that all organisms are made of cells - Schleiden and Schwann

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is resolution

A

the ability to distinguish two objects that are close to each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the smallest organelle that can be seen clearly by light microscopy

A

mitochondria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the issue with magnification ** on exam or final

A

we can magnify an image as much as we want, but it may be blurry (due to resolution)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is detection ** on exam or final

A

the ability to see something (an item smaller than 0.2 um can be detected if it emits light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the limit of resolution for microscopy

A

the wavelength of the light and the size of the lens

- the bigger the lens, the bigger resolution you can get

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

why are cells hard to visualize

A

they are colorless and translucent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what do phase-contrast and differential-interference-contrast microscopy do and what is the result

A

they use the change in phase of light waves as they pass through a cell
- gets the visualization of live, un-manipulated cells, but have limited detail

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the pro and con of staining with chemical dyes

A

pro - chemical dyes can reveal details of cells

con - requires fixation (kills and preserves cells)

17
Q

how can tissue samples be visualized

A

they have to be cut into thin sections because they are so large

18
Q

how do chemical dyes work

A

by absorbing specific wavelengths of light so the intensity of light goes down
- fluorescent molecules absorb light at one wavelength and emit light of a longer wavelength

19
Q

what does fluorescence microscopy allow for

A

detection of very small numbers of fluorescent molecules since they are viewed against a dark background

20
Q

how can fluorescent stains be introduced

A
  • chemical dyes
  • fluorescent molecules attached to antibodies
  • intrinsically fluorescent proteins expressed by cell itself (GFP - green fluorescent protein)
21
Q

how does fluorescent microscopy work

A

uses barrier filters and beam-splitting mirror to let in certain wavelengths, transmit light, then cut out unwanted fluorescent signals and be seen through eyepiece

22
Q

how is fluorescence microscopy limited

A

by fluorescence coming from out-of-focus parts of cells, which reduces practical resolution

23
Q

how does confocal microscopy work

A

uses a scanning laser and pinhole apertures to limit detection to the focal plane - creation of an optical section with much better resolution = no need to slice the cell

24
Q

what type of image of a sample can be reconstructed using confocal microscopy

A

3D images - formed by taking images from various focal planes (“z sections”)

25
Q

how does FRET work

A

fluorescence resonance energy transfer - uses 2 fluorescent proteins where the excitation energy of the 2nd matches the emission of the first. if 2 are very close together, exciting protein 1 will allow protein 2 to fluoresce
- can tell if the molecules are in contact with each other

26
Q

how does 2-photon microscopy work

A

2 separate long-wave photons of light excite the fluorophore. this allows for deeper penetration into a sample without sectioning (“vital microscopy”)

27
Q

what occurs with a long wavelength

A

the longer the wavelength, the further it can get into the sample before it’s absorbed

28
Q

what occurs with a shorter wavelength

A

the shorter the wavelength, the higher the energy

29
Q

how does electron microscopy work

A

a focused beam of electrons replaces light - more than 200x increase in resolution than light microscopy

30
Q

why is a vacuum required in electron microscopy

A

so electrons don’t bounce. cells must be fixed and desiccated and then sliced into ultra-thin sections

31
Q

when do you have to use light microscopy specifically

A

when using live samples

32
Q

how do scientists solve the issue of cells being mostly transparent to electrons

A

electron-dense materials are used to stain cells. can also use gold-tagged antibodies to mark specific proteins/structures

33
Q

what colors do electron microscopy show up in

A

black and white

34
Q

what is SEM (scanning electron microscopy)

A

3D - images the outside surface - uses staining but no sectioning

35
Q

what is TEM (transmission electron microscopy)

A

2D - images internal structures - sliced ultra thin

36
Q

what does an electron beam give more resolution than light

A

because the wavelength of an electron is much shorter than the wavelength of a photon

37
Q

what is a simple definition of flow cytometry

A

single cell analysis - live cells are analyzed in real-time in an aqueous stream as they pass through a laser and a computer collects fluorescence data and laser scatter