methods of studying cells

Question 1

what is cell fractionation used for?

Answer 1

• used to isolate different organelles so they can be studied
• ## enables individual organelle structures and functions to be studied

Question 2

what happens during cell fractionation

Answer 2

• cells are broken open to release contents
• are then seperated

Question 3

why must solution be cold?

Answer 3

• to reduce enzyme activity (enzymes could damage organelles)

Question 4

why must solution be isotonic?

Answer 4

• so it is same water potential
• to prevent osmosis , which might cause ORGANELLES to shrivel or burst

dont write “causes CELL to burst”

Question 5

why is solution buffered?

Answer 5

ph is buffered to prevent damage to organelles

Question 6

How is cell fractionation and ultracentrifugation used to isolate organelles from cells?

Answer 6

• cell is homogenised (broken open) using blender
• in cold,isotonic, buffered solution
• solution is filtered to remove large cell debris
• solution is spun at different speeds in centrifuge
• organelles separate according to their densities
• organelles that are most dense form at the bottom
• each time the supernatant (Liquid) is removed
• supernatant is spun again at increasing speed to remove next pellet of organelles

Question 7

what is the order in which organelles centriguge out?

Answer 7

1) nuclei
2) chloroplasts (ONLY IF USING PLANT TISSUE)
3) mitochondria
4) lysosomes
5) endoplasmic reticulum
6) ribosomes

Question 8

compare transmission electron microscopes and scanning electron microscopes

Answer 8

Differences:
- TEMs give higher resolution images than SEMs
- SEMs can be used on thick specimens, whereas TEMs can only be used on thin specimens
- SEMs produce a 3D image, TEMs produce 2-D image

Similarities:
- both use electrons to produce an image
- both can only be used on nonliving specimens
- both have higher resolution than optical microscopes

Question 9

compare light and electron microscopes

Answer 9

• light microscopes have max resolution of 0.2 um, whereas, electron microscopes have resolution up to 0.0002 um (EMs have greater resolution)
• light microscopes can view living speciment, whereas, electron microscopes cannot
• electron microscopes have higher magnification than light microscopes