cell fractionation and magnification Flashcards
define cell fractionation:
process of breaking up cells to produce pure fractions ( smaller parts) of cell component
what are the two steps of cell fractionation
-Homogenation: disrupting the tissue+ lysis of the cells
-ultracentrifiguation: process by which the homogenate is separated in a machine
called a centrifuge
+
spins tubes of the homogenate, creating a centrifugal force that makes the mixture separate.
describe the process of homogenation
-Cells are broken up by a homogeniser that releases the organelles
-fluid is called a homogenate.
-it is then filtered to remove unbroken cells + any debris.
describe the process of ultracentrifugation
-The tube of filtrate is placed in the ultracentrifuge and spun at a slow speed.
* The heaviest organelles such as the nucleus are forced to the bottom where
they form a thin sediment.
* The fluid at the top, called the supernatant is removed, leaving just the
sediment of nuclei at the bottom.
* The supernatant is then put in another tube where it is spun at an even higher
speed than before.
* The next heaviest organelles (mitochondria) are forced to the bottom and the process continues until all the organelles are separated.
Contrast how an optical microscope and a transmission electron
microscope work and contrast the limitations of their use when studying
cells. (6)
- TEM uses electrons and optical uses light
-TEM allows a greater resolution;
-TEM smaller organelles can be
observed
-TEM can only view dead specimens.
-TEM does not show colour and optical (can);
-TEM requires thinner specimens;
Explain why the solution the biologist used was ice-cold, buffered and the
same water potential as the liver tissue
-Ice Cold: stops enzyme activity to prevent digestion of organelles
-buffered: Maintains pH so that enzymes are not denatured.
-same water potential:Prevents osmosis so no shrinkage of organelles
