Lecture 3: How Cells are Studied I Flashcards
The shorter the wavelength of incidence the better the resolution (T/F)
True.
- visible light of shortest wavelength (blue) = 450 nm, whereas an electron wavelength= 0.004 nm.
- the resolution of an electron microscope should* be 100 000 x greater.
In fixed stained cells the incident light waves are in phase (T/F)
True. Only the amplitude passing through the stained portion is reduced.
Define dark-field microscopy
- observes the light that is scattered by components of a living cell.
- illuminating is directed from the side ensuring that only scattered light enters.
- illuminates membranes.
Success of immunogold labelling technique depends on
(1) antigen-primary antibody specification.
(2) antibody’ ability to infiltrate cells and tissues.
The use of immersion oil reduces “D” by 33% thus improving resolution (T/F)
True.
Define the resolution of a microscope
the ability of a microscope to distinguish two objects close to each other.
The total magnification of a optical microscope is the product of
both ocular and objective lenses.
example: objective lens; 100-fold, ocular lens; 10-fold.
total magnification= 10 x 100= 1000-fold microscope.
How does immunogold microscopy unfold
- a primary antibody is designed to bind onto a specific antigen.
- gold conjugated secondary antibody binds to primary antibody.
Many chemical stains bind to molecules that have specific features such as
(1) Hematoxylin acidic side chains of amino acids (aspartame and glutamate) of proteins as well as to DNA and RNA.
(2) Eosin binds mostly to basic side chains of amino acids (lysine and arginine) of proteins.
Magnification is the most important property of a optical microscope (T/F)
False. The resolution is the most important property of a optical microscope.
What are the parts of an optical microscope from bottom to top
- lamp field stop; restricts the amount of light entering a lens (works like a diaphragm).
- base with light source
- condenser lenses; focus light on specimen of investigation and DO NOT create magnification.
- specimen on stage; mounted on transparent glass slide.
- objective lenses; (a) pick up light transmitted by specimen, (b) focus it on focal plane of objective lens, (c) WILL create magnified image.
- reflecting prism
- focal plane of objective lens
- ocular lens; (a) pick up magnified image from focal plane of objective lens, (c) focus this additionally magnified image.
- line of vision; light picked up by ocular lens by additional magnified image and projects it onto the plane of the human eye
What is the optical pathway of modern compound optical microscope
From lamp field stop to line of vision (bottom to top).
n x sin α is called
the numerical aperture, and is a function of its light collecting abilities.
What are the four types of light microscopy
(1) bright field microscope.
(2) phase-contrast microscopy.
(3) Normaski differential-interference-contrast (DIC) microscopy.
(4) dark field microscopy.
The shorter the wavelength, the lower will be the value of D and the better the resolution however
Yes, in theory the resolution would be better however in reality an electron microscope is only 1000x better because taking the air out of electron microscope dramatically decreases the value of “n”.
