Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Cell Biology > Lecture 4 Reading Chapter 9 visualizing cells > Flashcards

Lecture 4 Reading Chapter 9 visualizing cells Flashcards

0
Q

Scope of light microscope

A

0.4-0.7 micrometers

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

Cell doctrine

A

All plants and animal tissues are aggregated of individual cells. Schleiden and Schwann, 1838

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

Optical diffraction effects

A

Light waves travel through different routes, and not in a straight line, so they interfere with each other

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

In phase

A

Interference makes things brighter

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

Out of phase

A

Light waves interfere with each other in such a way as to cancel each other partly or entirely

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

Micrometer

A

10^-6 m

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

Nanometer

A

10^-9 meters

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

Angstrom

A

10^-10 meters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Limit of resolution

A

The limiting separation at which two objects appear distinct. Depends on wavelength of light and numerical aperture of lens system used.

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

How does numerical aperture work

A

Affects the light gathering ability of the lens and is related both to the angle of the cone of light that can enter it and to the refractive index of the medium the lens is operating I

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

Refractive index

A

Ratio of the speed of light in a vacuum to the speed of light in a particular transparent medium

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

How can contrast in a specimen be generated

A

Light microscopes with special optical systems

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

Bright field microscope

A

Light passing through a cell in culture forms the image directly

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

Dark field microscopy

A

Exploits the fact that light rays can be scattered in all directions by small objects in their path. Bright image against a black background

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

How does light change as it passes through a cell

A

The phase of the light wave is changed according to the cell’s refractive index.

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

How do phase contrast microscope and differential interference contrast microscope work

A

Increase phase differences caused by cell’s refractive index so that waves are more nearly out of phase, producing amplitude differences when the sets of waves recombine, thereby creating an image of the cell’s structure

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

How do we increase our ability to observe cells

A

We can attach a sensitive digital camera to a microscope, the camera detects light by means of charged coupled devices(CCDs) or high sensitivity complementary metal-oxide semiconductors (CMOs) sensors. These sensors are ten times more sensitive than naked human eye and can detect 100 times more intensity levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do we prepare tissue for microscopy

A

Fix and section tissue, then freeze or embed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Sections

A

Very thin transparent slices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Fixative

A

Forms covalent bonds with the free amino groups of proteins, cross linking the, so that they are stabilized and locked in position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Usual embedding medium for tissue

A

Waxes or resins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Three main approaches to working with thin tissue sections that reveal differences in types of molecules that are present

A

Sections can be stained with organic dyesthat have some specific affinity for particular subcellular components
Sectioned tissues can be used to visualize specific patterns of differential gene expression
Using fluorescent probes and markers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How do fluorescent molecules absorb and emit light

A

Absorb light at one wavelength and emit it at a longer wavelength.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Fluorescence microscope

A

Tool to visualize fluorescent dyes for staining cells. Illuminating light is passed through two sets of filters. One to filter the light before it reaches the specimen and one to filter the light obtained from the specimen,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

When is fluorescence microscopy used

A

Ro detect specific proteins or other molecules in cells and tissues

25
Q

How are antibodies used with fluorescent dyes

A

They are coupled. The. Antibody molecules serve as highly specific and versatile staining reagents that bind selectively to the particular macromolecules they recognize in cells or in the extracellular matrix.

26
Q

What two dyes are used with antibodies frequently

A

Fluorescein , emits intense green fluorescence when excited with blue light
Rhodamine, emits deep red fluorescence when excited with green-yellow light

27
Q

Quantum dots

A

Tiny crystals of semiconductor metal that can be excited to fluoresce by a broad spectrum of blue light

28
Q

How are antibodies prepared for microscopy

A

Either purified from antiserum so as to remove all nonspecific antibodies, or they are specific monoclonal antibodies that only recognize the target molecule

29
Q

Indirect immunocytochemistry

A

Using an unlabeled primary antibody and then detecting it with a group of labeled secondary antibodies that bind to it

30
Q

Two ways to solve out of focus problem

A

Give many sectional views of optical sections

Image deconvolution

31
Q

Image deconvolution

A

Computer calculates what blurring would have done and reverses

32
Q

Point spread function

A

Blurred image of a point source

33
Q

Confocal microscope

A

Manipulates light before it is measures. Analog technique.

Generally used with fluorescent optics. Focused on single point not ph whole object

34
Q

Thick specimens are viewed with

A

Multi photon microscopes, with two-photon effect.

35
Q

Green fluorescent protein (GFP)

A

Isolated from a jellyfish. Encoded by a single that can be cloned and introduced into cells of other species

36
Q

How is GFP used usually

A

As a reporter molecule, a fluorescent probe to monitor gene expression

37
Q

How do we use fluorescent proteins to uncover kinetic properties of a cell

A

Fluorescence resonance energy transfer (FRET)
Photoactivation
Fluorescence recovery after photo bleaching (FRAP)

38
Q

FRET

A

Teo molecules of interest are each labeled with a different fluorochrome, chosen so that the emission spectrum of one fluorochrome, the donor, overlaps with the absorption spectrum of the other, the acceptor.

39
Q

Photoactivation

A

Fluorescence tagging technique that allows detailed observations of proteins within cells. Involves synthesizing an inactive form of the fluorescent molecule of interest, introducing it into the cell, and then activating it suddenly at a chosen site in the cell by focusing a spot light on it.

40
Q

Caged molecules

A

Inactive photosensitive precursors

41
Q

Fluorescence recovery after photo bleaching (FRAP)

A

One uses a strong beam of light from a laser to extinguish the GFP fluorescence in a specified region of the cell, after which one can analyze the way in which remaining unbleached fluorescent protein molecules move into the bleached area as a function of time.

42
Q

Why are micro electrodes not good at measuring changing ion concentrations

A

They reveal ion concentration only at one point of cell

43
Q

Ion sensitive indicators

A

Suited to record rapid and transient changes in ion concentration. Have light emission that reflects local concentration of ion.

44
Q

Aequorin

A

Luminescent protein. Emits blue light in presence of Ca2+, and responds to changes in concentration in the range of 0.5-10 micrometers.

45
Q

Genetically encoded fluorescent indicators

A

Bind ion tightly. Are excited by or emit light at slightly different wavelengths when they are free of io than when bound. By measuring the ratio of fluorescence intensity at two excitation or emission wavelengths, one can determine concentration ratio of ion bound indicator to the free indicator and get a measurement of ion.

46
Q

Why can’t single fluorescent molecules be reliably detected in ordinary microscopes

A

Limitation arises from the strong background due to light emitted or scattered by out-of-focus molecules. This tends to blot out the fluorescence from the particular molecule of interest.

47
Q

Total internal reflection fluorescence (TIRF) microscopy

A

Because of total internal reflection, light does not enter sample, so majority of fluorescent molecules are not illuminated. Electromagnetic energy does extend, as an evanescence field, for a short distance beyond the surface of the cover slip and into the specimen, allowing just those molecules in the layer closest to the surface to become excited.

48
Q

Atomic force microscopy (AFM)

A

Provides a method to manipulate individual molecules. With its tip, probe can collect data on the variety of forces it encounters.

49
Q

Approaches in light microscopy that bypass resolution imposed by diffraction of light. Superresolution approaches

A

Structured illumination microscopy (SIM)
Stimulated emission depletion microscopy (STED)
Photo activated localization microscopy (PALM)

50
Q

Structured illumination microscopy SIM

A

Fluorescence imaging method with resolution of about 100 nm.uses grated or structured pattern of light to illuminate the sample. Illuminating grid and sample features combine into an interference pattern, from which the original high resolution contributions to the image beyond the classical resolution can be measures. Imaging is repeated several times and then combined mathematically to create an enhanced image.

51
Q

Point spread function

A

Distribution of light intensity within the three dimensional, blurred image that is formed when a single point source of light is brought to a focus with a lens.

52
Q

Stimulated emission depletion microscopy DTED

A

Increasing resolution by switching all the fluorescent molecules at the periphery of the blurry excitation spot back to their ground state, where they no longer fluoresce in their normal way. Diffraction limit breached because technique ensures that similar but very closely spaced molecules are in one of two different states, either fluorescing or dark.

53
Q

Photo activated localization microscopy (PALM)

A

Labels are activated by illumination with near UV light. A small subset of molecules is modified so that they fluoresce when exposed to an excitation beam at another wavelength. These switch and another subset is activates. The photons of each subset given off are recorded and then aggregated into an image.

54
Q

Preparing a specimen for electron microscopy

A

Living tissue is killed and preserved by fixation, usually with glutaraldehyde and osmium tetroxide, which binds to and stabilizes lipid bilayers as well as proteins. Cut into extremely thin sections.

55
Q

What does image clarity depend on in an electron micrograph?

A

A range of contrasting electron densities. Impregnate tissues with salts of heavy metals.

56
Q

Immunoglobulins electron microscopy

A

Incubate a thin section with a specific primary antibody, and then with a secondary antibody to which a colloidal gold particle has been attached.

57
Q

Creating a third dimension view of a specimen

A

Have views of the same specimen from many different directions

58
Q

Electron microscope tomography

A

Specimen holder is tilted to arrive at a 3d view

59
Q

Scanning electron microscope (SEM)

A

Directly produces an image of the three dimensional structure of the surface of a specimen. Uses electrons that are scattered or emitted from the specimen’s surface.

60
Q

Negative staining

A

Allows finer detail of macromolecules to be seen. Molecules are supported on a thin film of carbon and mixed with a solution of heavy metal salt. Creates reverse or negative image of molecule.

Cell Biology (35 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions