methods of studying cells Flashcards
microscopes, ultracentrifugation
magnification
how many times larger an image is than the object
resolution
the ability to distinguish between two points (resolving power)
diaphragm and condenser
underneath the stage to let light pass through
optical microscopes
- max mag usually x1500
- max res is 200nm
- uses light to create images, and uses glass to focus images
- specimens can be alive when viewed
- thin slides to allow light to penetrate
issues with optical microscopes
- low mag and res
- limited structure can be viewed
- risk of artefacts
electron microscopes
- mag of x1,500,000
- res as great as 0.1nm as they provide a shorter wavelength
- produces black and white images that can be 2D (TEM) or 3D (SEM)
- specimens must be dead as electrons are used in a vacuum
- focuses images with magnets
calculating magnification
image size/actual size
issues with electron microscopes
- electrons can damage specimens
- can only view dead objects
- staining required but not coloured images produced
- specimens must be thin
- risk of artefacts
cell fractionation
process of breaking cells open and separating the different organelles
steps of ultracentrifugation
1) homogenisation - using a blender 2) filtration - using a gauze 3) centrifugation - remove pellets and repeat with supernatant
conditions of homogenisation
- ice cold: to reduce enzyme activity and digestion of organelle
- isotonic : to stop osmosis and prevent cells shrinking or bursting
- buffer pH: to reduce damage to proteins
order of organelles homogenised (heaviest first)
nuclei, mitochondrion, chloroplast, lysosomes, ER, ribosomes
how is an eyepiece graticule calibrated?
by comparing the length of each division in the micrometer to the length of each division in the graticule.
eyepiece graticule
a glass disc in the eyepiece of a microscope.
