3.1 methods of studying cells Flashcards
What are microscopes
- Instruments that produce a magnified image of an object.
Why do electron microscopes have a higher resolution than light microscopes
. Light waves have a long wavelength so a light microscope can only distinguish between two objects if they are 0.2qm apart
. Beams of electrons can be used rather than beams of light as they have shorter wavelengths so electron microscopes distinguish between two objects if they’re 0.1nm apart.
Equation for magnification
Magnification =
Image size / actual size
What is the material that is put under the microscope known as
What is that material viewed under a microscope called
The object
Image
What is a kilometre in metres
What is a millimetre in metres
What is a micrometre in metres qm
What is a nanometre in metres
km= 1000metres
mm= 10^-3 or 0.001metres
qm= 10^-6
nm: 10^-9
What is the resolution of a microscope
What does the resolution of a microscope depend on
The minimum distance apart that two objects can be in order for them to appear as separate items.
Eg in a light microscope with resolution 0.2qm, any two objects that are this far apart will be seen separately, but any closer will appear as one item.
It depends on the wavelength or form of radiation used.
What happens when a microscope has reached its limit of resolution
. Increasing magnificaton will no longer reveal more detail so the object will appear larger but blurry
What is cell fractionation
The process where cells are broken up and the different organelles in them are separated out.
It is done because in order to study the structure and function of the various organelles that are in cells, you need to gain large numbers of isolated cells.
What conditions must there be before cell fractionation can begin
What are the reasons for these
. The tissue is placed in a cold, buffered, isotonic solution
. Cold to reduce enzyme activity that might break down the organelles
. Its buffered so the PH doesn’t fluctuate: any change in ph could alter the structure of the organelles or affect the functioning of enzymes
. It is of the same water potential as the tissue to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water
What is the stage 1 of cell fractionation called Homogenation
. Cells are broken up by a homogeniser/ blender which releases the organelles from the cell
. The resultant fluid known as the homogenate can be filtered to remove any complete cells and large pieces of depris
What is Ultracentrifugation
Stage 2 of cell fractionation where the fragments in the filtered homogenate are put in a centrifuge that spins them very fast and separates them
Describe the process of ultracentrifugation
. Tube of filtrate is placed in the centrifuge and spun at a slow speed for 10 minutes
. The heaviest organelles, the nuclei are forced to the bottom of the centrifuge tube where they form a thin sediment or pellet
. The fluid at the top of the tube (supernatant) is removed, leaving the sediment of nuclei
. The supernatant is transferred to another tube and spun in the centrifuge at a faster rate
. The next heaviest organelles, the mitochondria are forced to the bottom of the tube
Then lysosomes are next
. The process is continued this way so with each increase in speed , the next heaviest organelle is sedimented and separated.
What is the speed of centrifugation for these organelles to be separated out
Nuclei
Mitochondria
Lysosomes
Nuclei: 1000
Mitochondria: 3500
Lysosomes: 16500
