chapter 2 Flashcards
why is staining used
to create contrast
to differentiate between different types not cells
cells are transparent
to show diff structures
differences between LM AND EM
EM- vacuum, x500,000 mag , specimens dead, uses beam of electrons
LM- no vacuum x2000 mag, living or dead, uses light
what is chromatic aberration
unable to bring all wavelengths of color together
what is a cell theory
A,B,B,C,C,D,E
both plant and animal tissue is composed of cell
cells are the basic unit of life
cells only develop from existing cells
what is magnification
is how many times larger the image than the actual size of the image being viewed
what is resolution
ability to see individual objects as separate entities
magnification= ?
size of image/ actual size of object
scientific drawings need?
include a title state magnification use sharp pencil uses as much paper as possible smooth continuous lines do not shade no arrow heads
what is a dry mount
solid specimen cut into very thin slices with a sharp blade called sectioning specimen placed onto centre of slide and cover slip placed onto of sample
e.g: hair pollen dust , muscle tissue viewed in this way
wet mount
specimen suspended in liquid such as water or emersion oil cover slip placed an angle eg. aquatic samples viewed
what is squash slide
wet mount then lease tissue used gently press down cover slip. using squash slides good techniques for soft samples. care need to be taken cover slip to broken eg root tip squashes used to look at cell division
what is smear slides
edge of a slide used to smear sample creating thin veneer coating on another slide cover slip placed angle 45 degrees
what is diffraction
bending of light passes close to edge of object
what is fixing
chemical like formaldehyde preserve specimens in near natural state as possible
what is sectioning
specimens dehydrated with alcohols placed in mold to form a hard block
what is mounting
specimen secured to micro scope slide and cover slip ontop
how can resolution be increased
using beams of electrons
transmen
beams of electrons transmitted through a specimen and focused to produce an image
2D
0.5nm x 500,000
sem
beams of e- sent across surface of specimen reflected electrons collected
3D
3-10nm
x 500,000
prep for TEM in EM
set in resin may be stained again
prep for SEM in EM
expose inside coated with heavy metal
what is artifact
appear in EM and LM bubbles get trapped under cover slip or distortion of organelles
what is fluorescence
absorption and re radiation of light
what is beam splitter
dichroic mirror only reflects one wavelength but allows other wavelengths
