3.1- METHODS OF STUDYING CELLS Flashcards
What are microscopes?
instruments that produce magnified image of object
What can act as a simple magnifying glass?
simple convex glass lens
How can simple convex glass lenses work more effectively?
when they’re used in pairs in a compound light microscope
What sort of wavelength do light rays have?
long wavelength
What does light rays having long wavelengths mean?
light microscope can only distinguish between two objects if they’re 0.2μm or further apart
How can the limitation of light microscopes only being able to distinguish between two objects if they’re 0.2μm or further apart, be overcome?
by using beams of electrons rather than beams of light
What is the wavelength of electrons like in comparison to wavelength of light rays?
shorter wavelength
What are electron microscopes able to as electrons have a shorter wavelength?
beam of electrons in electron microscope can distinguish between two objects only 0.1nm apart
What is the material that is put under a microscope referred to as?
object
What is the appearance of the material when viewed under the microscope referred to as?
image
What is the magnification of an object?
how many times bigger the image is when compared to the object
magnification equation:
magnification=
size of real objects
What is the resolution or resolving power of a microscope?
minimum distance apart that two objects can be in order for them to appear as separate items
What does the resolving power depend on?
wavelength or form of radiation used
What is the approximate resolution power in a light microscope?
about 0.2 μm
What does a light microscope having a resolving power of 0.2 μm mean?
any two objects which are 0.2 μm or more apart will be seen separately, but any objects closer than 0.2 μm will appear as a single item
What does a greater resolution result in?
greater clarity
image produced is clearer and more precise
How does increasing the magnification affect the size of the image and resolution?
increases the size of the image, but doesn’t always increase the resolution
Does every microscope have a limit of resolution?
yes
What will happen beyond the limit of resolution?
increasing the magnification will reveal more detail but beyond this point increasing magnification will not do this
object will appear larger and more blurred
What is necessary to study the structure and function of the various organelles?
to obtain large numbers of isolated organelles
What is cell fractionation?
process where cells broken up and different organelles they contain separated out
What happens before cell fractionation can begin?
tissue placed in cold, buffered solution of same water potential as tissue
Why is the solution cold?
reduce enzyme activity that might break down the organelles
Why does the solution have the same water potential as the tissue?
prevent organelles bursting/shrinking due to osmotic gain or loss of water
Why is the solution buffered?
so the pH doesn’t fluctuate
any change in pH could alter the structure of organelles or affect functioning of enzymes
How many stages are there in cell fractionation?
two
What are the two stages in cell fractionation?
homogenation
ultracentrifugation
How are cells broken up?
by a homogeniser (blender)
What does the homogeniser do?
release organelles from cell
What is the resultant fluid from the homogeniser known as?
homogenate
What is done with the homogenate?
filtered to remove any complete cells and large pieces of debris
What is ultracentrifugation?
process by which fragments in filtered homogenate separated in machine called centrifuge
What does the centrifuge do?
spins tubes of homogenate at very high speed in order to create a centrifugal force
process of ultracentrifugation of animal cell (1)
tube of filtrate placed in centrifuge and spun at low speed
process of ultracentrifugation of animal cell (2)
heaviest organelles, nuclei, forced to bottom of tube, where they form thin sediment/ pellet
process of ultracentrifugation of animal cell (3)
fluid at top of tube (supernatant) removed, leaving just sediment of nuclei
process of ultracentrifugation of animal cell (4)
supernatant transferred to another tube and spun in centrifuge at faster speed than before
process of ultracentrifugation of animal cell (5)
next heaviest organelles, mitochondria. forced to bottom of tube
process of ultracentrifugation of animal cell (6)
process continued in this way so that, at each increase in speed, next heaviest organelle sedimented and separated out
speed of centrifugation for nuclei?
1000 revolutions per min
speed of centrifugation for mitochondria?
35000 revolutions per min
speed of centrifugation for lysosomes?
16500 revolutions per min
what did the techniques of cell fractionation and ultracentrifugation enable?
considerable advances in biological knowledge
What did cell fractionation and ultracentrifugation allow?
detailed study of structure and function of organelles, by showing what isolated components do
