CELLS 1 (fractionation, microscopes & viruses) Flashcards
what is the resolution of an optical microscope (light)?
200nm
what is the resolution of a SEM microscope?
20nm
what is the resolution of a TEM microscope?
0.1nm
which type of microscope forms coloured images?
Light only. NOT ANY ELECTRON
which microscope type produces 3D images?
SEM
what is the difference in electron beam firing in the two types of electron microscope?
SEM: electron beam fired and bounce off of sample, then focus on a fluorescent screen
TEM: electron beams fired through sample
Which microscope has biggest resolution and magnification?
transmission electron microscope
equation for magnification
mag = image/actual
I
A M
what’s some drawbacks of an electron microscope?
B+W image only, expensive, need training to use, samples in vacuum ( electrons absorbed by air)
why is electron microscope sample in a vacuum?
Electrons are absorbed by the air, so the beam wouldn’t reach the specimen.
what is the relationship between wavelength and resolution?
inversely proportional.
increase wavelength = down res.
why is the resolution higher in a TEM microscope than light microscope?
light has a longer wavelength than electrons.
how to convert between micrometers (μm) and nanometres (nm)
μm -> nm
= x1000
mm -> μm conversion
x1000
define resolution
the ability to distinguish between 2 points on an image
what is the order of units. biggest to smallest?
cm -> mm -> μm -> nm
define magnification
how much bigger a sample appears to be under a microscope than it is irl.
positives of a light microscope over electron.
portable, cheap, easy to use, live samples, colour image
define cell fractionation
separating cell organelles out by breaking them up to produce a pure sample of one organelle
order of density of organelles
nucleus, chloroplast, mitochondria, lysosomes, rough er, plasma membrane, smooth er, ribosomes
which organelle is separated last into the pellet in cell fractionation?
ribosomes
which organelle is separated first into the pellet in cell fractionation?
nucleus
what are organelles separated by in cell fractionation?
order of density. biggest to smallest.
what is meant by homogenisation in cell fractionation?
when the cells are broken open in a blender or homogeniser
what are samples spun in during cell fractionation?
centrifuge
what is the liquid that rises in cell fractionation called?
The supernatant, re-spunfaster each time until only pellet remains.
why do you put the tissues into ice cold mixture in in cell fractionation?
To reduce enzyme activity to prevent digestion of organelles
why do you put the tissues into isotonic mixture in cell fractionation?
it has the same water potential as the tissue to prevent osmotic damage eg shrinking due to pressure changes
why do you put the tissues into buffer solution in cell fractionation?
so the pH is constant to avoid protein denaturation
what is the role of cell fractionation
to study a particular organelles function and structure
what type of cell is a virus?
its acellular because it does not have a cellular structure
what’s a virus made of?
nucleic acids surrounded by capsid proteins
what’s a viruses capsid?
The protein coat around the nucleic acid virus core
how do viruses replicate?
- attachment proteins to bind to complementary receptor proteins on a host cell surface
- inject dna to host cells
- host cell replicates
what’s the role of attachment proteins on a virus?
- to bind to host cells in order to replicate.
what enzyme do viruses use to insert its RNA into host cells dna
reverse transcriptase enzymes
