Analysis of cell components part 2

Question 1

• what organelles can you not view with an optical microscope

Answer 1

ribosomes, the endoplasmic reticulum and lysosomes.

you may be able to work out mitochondria but not in perfect detail

Question 2

• what is the maximum useful magnification of an optical microscope

Answer 2

x1500

Question 3

• what is the maximum useful magnification of an electron microscope

Answer 3

x 1 500 000

Question 4

• Explain how you prepare a temporary mount of a specimen on a slide

Answer 4

start by pipetting a small drop of water onto the slide.

then use tweezers to place a thin section of your specimen on top of the water drop

add a drop of a stain. stains are used to highlight objects in a cell.

finally add the cover slip.

to do so stand the slip upright on the slide, next to the water droplet.

then carefully tilt and lower it so it covers the specimen.

Question 5

• what should we aviod in the cover slip and why

Answer 5

air bubbles

this is because theyll abstruct your view od the specimen

Question 6

• define cell fractionation

Answer 6

cell fractionation is the process where cells are broken up and the different organelles they contain are spread out

Question 7

• what happens before cell fractionation can begin

Answer 7

thhe tissure is placed in a cold, buffered solution of the same water potential as the tissue

Question 8

• describe the solution used for cell fractionation

Answer 8

cold- to reduce enzyme activity that might break down organelles

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

buffered- so that the pH does not fluctuate. Any change in pH could alter the structure of the organelles or affect the functioning of enzymes

Question 9

• explain the stage of homogenation

Answer 9

cells are broken up by a homogeniser. this releases the organelles from the cell.

the resultant fluid, known as homogenate, is then filtered to remove any complete cells and large pieces of debris

Question 10

• define and explain ultracentrifugation

Answer 10

ultracentrifugation is the process by which the fragment in the filtered homogenate are separated in a machine called a centrifuge

this spins tubes of homogenate at very high speeds in order to create a centrifugal force

Question 11

• For animal cells what is the process of ultracentrifugation

Answer 11

the tube of filtrate is plaves in the centrifuge and spun at a slow speed

the heaviest organelles, the nuclei, are forced to the bottom of the tube, where they form a thin sediment or pellet

the fluid at the top of the tube (supernatant) is removed, leaving just the sediment of nuclei

the supernatant is transferred to another tube and spun in the centrifuge at a faster speed than before

the next heaviest organelles, the mitochondria, are forced to the bottom of the tube

the process is continued in this wat so that at each increase in speed, the next heaviest organelle is sedimented and separarted out

Question 12

• how are the organelles separated in cell fractionation

Answer 12

the organelles are separated in order of mass

this order is usually nuclei, mitochondria, lysosomes, endoplasmic reticulum and finally ribosomes