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