3.2.1.3 Methods of studying cells Flashcards
(22 cards)
What is magnification?
Magnification is how much bigger the image is then the specimen
What is resolution?
Resolution is the minimum distance apart that two objects can be in order for them to be distingushed as seperate items
Why does a light microscope have a low resolution?
It is limited due to the wavelenght of visible light
What is the equation which connects image size, actual size and magnification?
I = AM
What are the two types of microscopes?
Electron and Light
What is a light microscope?
They use light to from an image
Low magnification and resolution
What is an electron microscope?
They use electrons to from an image
High magnifcation and resolution
What are the two types of electron microscopes?
Scanning EM
Transmission EM
What is a TEM?
TEMs use electronmagenets to focus a beam of electron which go through the specimin
Give high resolution of internal organelles
What are the downsides to TEM?
Specimen is in a vacum and therefore will be dead
Specimen must be thin to allow for electrons to pass through
What is a SEM?
SEMs scan the specimen with a beam of electrons
High magnification
What are the downsides to SEM?
Only useful when looking at 3D images of specimen
Low resolution
What are microscope artefacts?
Artefacts are objects that you see in the microscope that aren’t the specimen
When are artefacts usally produced?
During the preperation of the specimen slide
What is cell fractionation?
The seperation of various organelles
Before Cell Fractionation can occur the specimen has to be placed in a solution that is …
Buffered - so that the pH remains constant otherwise the cell structure could alter
Cold - to reduce enzyme activity that might break down the organelles
Same water potential - to prevent cell lysis or plasmolysis due to an increase in gain or loss of mass
What are the three main steps of Cell Fractionation?
Homogenisation
Filtration
Ultracentrifugation
What is Homogenisation?
Cells are broken up by a homogeniser which releases the organelles from the cell and the liquid produced is known as the homogenate
Why is the homogenate filtered after homogenisation?
To remove any large debris or complete cells
What is the process of ultracentrifugation?
- The tube of filtrate is placed in the centrifuge and spun at low speed
- The heaviest organelle gets forced tod the bottom forming a pellet
- The fluid at the top (supernatant) gets removed, leaving just the pellet
- The supernatant is then transfered to another tube and is spun again
- The process is then repeat to get all of the organelles out
What is the order of organelles in animals?
Nuclei - mitochondria - lysosome - endoplasmic reticulum - ribosomes
What is the order of organelles in plants?
Nuclei - Chloroplasts - Mitochondria - Lysosomes - Endoplasmic reticulum - Ribosomes
