Cell structure and microscopy Flashcards
What do microscopes do?
Produce a magnified image of an object
What lenses are used in pairs in a compound light microscope by acting as a magnifying glass?
Convex glass lens
Why can light microscopes only distinguish between two objects if they are 0.2um (or further) apart?
Light rays have a relatively long wavelength
What can overcome the limitation of light rays’ wavelength?
Using beams of electrons rather than beams of light
How do the shorter wavelength beams of electron’s affect the microscope?
The microscope can distinguish between two objects only 0.1nm apart
What are the two main microscopes?
1) Light microscope
2) Electron microscope
What is the material that is put under the microscope called when
a) it is out of the microscope?
b) it is under the microscope?
a) the object
b) the image
What is magnification?
How many times bigger the image is compared to the object
What is the formula for calculating magnification?
M = Image size / actual size
How many nm make up a um?
1000
What is the resolution of a microscope?
The minimum distance apart that two objects can be in order for them to appear as separate items
Does a microscope using a longer wavelength (E.G. light microscope ) have a higher or lower resolution?
Lower resolution
Why do scientists isolate organelles?
To study the function and structure of the orgnanelles that make up cells
Why does an image that has increasing magnification appear more blurry?
Resolution is not increasing so magnification can no longer reveal any more detail
What is cell fractionation?
The process where cells are broken up and the different organelles they contain are separated out.
What 3 properties are supposed to be in the fractionating solution?
1) Cold
2) Buffered
3) same water potential as the tissue
Why must a fractionating solution be cold?
To reduce enzyme activity that might break down organelles
Why must the fractionating solution be the same water potential of the tissue - isotonic?
to prevent organelles bursting or shrinking as a result of osmotic gain or loss of water.
Why must the fractionating solution be buffered ?
So the pH does not fluctuate which could alter the structure of the organelles or affect the functioning of the enzymes
What are the 2 steps fractionation?
1) Homogenation
2) Ultracentrifugation
What is homogenation?
The breaking up of cells which releases the organelles into a homogenate fluid.
What do you do to the homogenate before ultracentrifugation?
It is filtered to remove any complete cells and large pieces of debris
What is ultracentrifugation?
The process by which fragments in the filtered homogenate are separated in a centrifuge
What does a centrifuge do?
Spins tubes at a very high speed to create a centrifugal force
