3.2.1.3 Methods Of Studying Cells Flashcards
What’s cell fractionation the process of
The process where a cell is ruptured (membrane/cell wall burst open)
What does cell fractionation enable
Enables organelles to be studied individually
How many steps are there to cell fractionation
3
What happens in step 1 of cell fractionation
The cell tissue is homogenised (broken up)
How does cell tissue get homogenised
In a blender under 3 very specific conditions
What are the 3 conditions for cell homogenisation
Ice cold water
Isotonic solution
Liquid has a buffer
What does using ice cold water for cell homogenisation prevent
Prevents enzyme activity that might damage organelles - prevents cells from being hydrolysed (broken down)
Prevents organelles from reacting with each other
What’s isotonic solutions and whys it useful
It has the same water potential as organelles so prevents osmosis into organelles
What does using an isotonic solution prevent
Organelles swelling/bursting/shrivelling
What does the solution being buffered prevent
Prevents/reduces changes in pH
Prevents denaturing of enzymes/proteins/organelles
What happens to the water in a cell in hypertonic solution
What happens to the cell
There’s more water in the cell so the water leaves it
The cell shrivels
What happens to the water in a cell in hypotonic solution
What happens to the cell
There’s more water outside so water fills the cell
The cell swells + bursts
Why can’t you study organelle in hypotonic solution
As it’s too damaged and not repairable
What’s step 2 of cell fractionation
The ruptured cells/organelles are filtered
What does filtering do in cell fractionation
Removes any debris (unwanted) that aren’t required for the study
What’s step 3 of cell fractionation
Ultracentrifugation
What happens in ultracentrifugation
Organelles are spun at high speeds in a centrifuge
In ultracentrifugation, what size organelle falls to the bottom of the tube first and why
Largest + heaviest organelles fall to the bottom first forming a pellet as spinning organelles increases gravitational pull
What do the lighter,smaller organelles form in in ultracentrifugation
The supernatant
What happens to the supernatant and the pellet
The supernatant is poured off and the pellet is removed
What is found in the pellet first and why
The nucleus
Is the heaviest organelle
What 4 organelles do you get next at medium spinning speed
Mitochondria
RER
Plasma membrane
SER
What organelles do you get finally at high spinning speed
Free ribosomes
What’s magnification
How much bigger a sample appears to be under the microscope than it is in real life
What’s resolution
The ability to distinguish between 2 points on an image (amount of detail)
What small distance apart means 2 objects can be see as 1
200nm
What’s the equation for total magnification
Total magnification = objective magnification x eyepiece magnification
What are the 2 types of microscope
Light microscope
Electron microscope
What’s another name for a light microscope
Optical microscope
What’s a light microscopes resolution
200nm
How can 2 objects only been seen by light microscope
If light can pass between them
4 different magnifications in a light microscope
X4, X10, X40, X100
3 advantages of a light microscope
Cheaper
Easier to use
Can see living specimens
2 disadvantages of light microscopes
Limited resolution
Limited magnification
What does the condenser lens do
Changes + controls amount of light
What do electron microscopes use instead of light
A beam of electrons
What’s the resolution like in electron microscopes and why
Higher resolution
As electrons have shorter wavelengths than light so we can see cell ultrastructure in much more detail
What’s an electron microscopes image produced on
A computer screen called a photomicrograph
2 advantages of an electron microscope
Higher resolution
Higher magnification
3 disadvantages of electron microscopes
Expensive
Heavy machinery
Electrons can’t see living cells as they get easily distracted/cell interaction (only cell tissue)
What are the 2types of electron microscopes
Transmission electron microscopes (TEM)
Scanning electron microscopes (SEM)
What’s the specimen got to be like in a TEM
dead and thin
What happens in a TEM
A beam of electrons is passed completely through a specimen
What can the specimen be like in a SEM
It can be thicker
What happens in a SEM
Electrons are directed at the specimen creating an image from the electrons that are reflected off the surface
What are TEMs and SEMs both in
Vacuums
3 features of a photomicrograph
Grainy
Flat
2D
B&W
What is used to focus the beam onto the specimen in TEMs
Condenser electromagnets
Why is detail never achieved in TEMs
Due to human error e.g staining/cutting thinly during preparation
Where is the gun placed in a TEM
Above the specimen
What’s the photomicrograph produced like from a SEM
3D
Does a TEM or SEM have lower resolution?
SEM
Where can the gun be in a SEM
Below the specimen
2 advantages of a TEM compared to a SEM
Higher resolution
Higher magnification
3 disadvantages of a TEM compared to a SEM
Image is 2D, B+W, grainy + flat
Have to be thin
Full detail never achieve (human error)
3 advantages of a SEM compared to a TEM
3D images
Gun can be below
Doesn’t have to be thin
1 disadvantage of a SEM compared to a TEM
Lower resolution
What’s the resolution like in an electron microscope
0.1nm
3 disadvantages of an electron microscope
Artefacts e.g air bubbles
Expensive
Vacuum needed
Skill + training needed
What are the 2 parts to preparing a specimen
Sectioning
Staining
What are specimens embedded in
Was
How many m in a km
1000m
How many cm in a m
How many mom in a m
100cm
1000mm
How do you get from mm to miceometre
X1000
How do you get from mm to mm
X 1,000,000
How do u get from nm to mm
/1000000
What’s the image equation
Image = actual image x magnification
