chaoter 2 - microscopes Flashcards
how does the stain, crystal violet or methylene blue work
they are positively charged which attracts to negatively charged materials in cytoplasm leading to staining
how do nigrosin or congo red stains work
they are negatively charged so are repelled by negatively charged cytosol so dye stays outside of cells , leaving cell unstained against stained background
what is differential staining
distingushing 2 types of organisms by staining
what is gram stam technique
seperates bacteria in 2 groups by applying crystal violet and iodine. This is washed with alcohol and gram-positive bacteria is retained
gram-negative is restained with counterstain ( safranin) which appears red
what is acid fast technique
differentiate species of mycobacterium from other bacteria. Lipid solvent carries carbolfushcin dye into cell and washed with alcohol but only mycbacterium retained dye
what is magnification
how many times larger the image is than the actual size of the object being viewed
what is resolution
the ability to see individual objects as seperate entities
what limits resolution
diffraction of light
magnification formula
size of image/ actual size of object
what is a transmission electron microscope
a beam of electrons transmitted through specimen and focused to produce image. This has best resolution. 0.5 nm
what is scanning electron microscope
beam of electrons sent across surface of specimen and reflected electrons are collected. 3-10nm. 3D images produced
what are the difference between light and electron microscope
light:
-inexpensive
-small
-simple sample prep
- vacuum not required
- colour seen
- 2000x magnification
-200nm
-specimen can be alive
electron:
-expensive
-large
-needs vacuum
- black and white image
- 200 000 x magnification
- 0.5nm
-specimens are dead
what is artefact
visible structural detail caused by processing the specimen and not feature of specimne
what is fluorescene
absorption and re-radiation of light for longer wavelength and lower energy to produce magnified image
what is a laser scanning confocal microscope
moves a single spot of focused light across a specimen causing fluorescence.
very high resolution
specimen must be thin
what is the function of nucleus
codes genetic information in the form of DNA molecules
DNA is contained within nuclear envelope to prevent damage from cytoplasm
nuclear envelope has nuclear pores
what is the function of nucleolus
nucleolus is an area within nucleus responsible for producing ribosome. Composed of proteins and RNA
what is the function of mitochondria
produces ATP
has double membrane. inner membrane folds to form crista and fluid interior is matrix
inner membrane has enzymes for aerobic respiration
mitochondria contained mDNA to create own enzymes
what are the function of vesicles and lysosomes
vesicles are membranous sacs for storage and transport roles
lysosomes are specialised vesicles that contain hydrolytic enzymes to break down waste material, break down pathogens ingested by phagocytic cells and in apoptosis
what is the function of cytoskeleton
controls movement of cell and organelles in cell
what are the 3 components of cytoskeleton
microfilament - contractile fibres formed from actin responsible for cell movment
microtubules - globular tubulin proteins form tubes that act as tracks for movement of vesicles. Forms spindles
intermediate fibres - give mechanical strength to cells and help maintain integrity
what is the function of centrioles
component of cytoskeleton composed of microtubules
2 centrioles form centrosome
wha is thefunction of flagella and cilia
flagella enable cells motility and detects chemical change
cilia beat in a rhythmitic manner creating a current cos fluids or objects such as mucus moves
what is ER
network of membranes enclosing flattened sacs called cisternae
