cell structure (analysing cell components)

Question 1

what is magnification?

Answer 1

how many times larger an image is compared to an object

Question 2

what is resolution?

Answer 2

the ability to distinguish between 2 objects

Question 3

what is an optical microscope?

Answer 3

microscope that uses light to form an image

Question 4

what are the advantages of an optical microscope?

Answer 4

colour image, can use living samples

Question 5

what are the disadvantages of an optical microscope?

Answer 5

low magnification, poor resolution

Question 6

what is the maximum resolution of an optical microscope?

Answer 6

0.2 micrometres

Question 7

what is the maximum useful resolution of an optical microscope?

Answer 7

x1500

Question 8

what is an electron microscope?

Answer 8

uses electrons to form an image

Question 9

what is the maximum resolution of an electron microscope?

Answer 9

0.0002 micrometres

Question 10

what is the maximum useful magnification of an electron microscope?

Answer 10

x1500000

Question 11

how does a transmission electron microscope work?

Answer 11

use electromagnets to focus a beam of electrons, which is then transmitted through the specimen, denser parts of the specimen absorb more electrons, which makes them appear darker on the image

Question 12

what are the advantages of TEMs?

Answer 12

high resolution images

Question 13

what are the disadvantages of TEMs?

Answer 13

2D image

only used on thin, dead specimens

Question 14

how do scanning electron microscopes work?

Answer 14

scan a beam of electrons across the specimen, which knocks of electrons from the specimen, which are gathered in a cathode ray tube to form an image

Question 15

what are the advantages of SEMs?

Answer 15

3D images

can be used on thick specimens

Question 16

what are the disadvantages of SEMs?

Answer 16

lower resolution images

Question 17

how do you prepare a temporary mount?

Answer 17

place a small drop of water onto the slide
use tweezers to place a thin section of the specimen on top of the water drop
add a drop of stain
add the cover slip
slowly tilt to avoid air bubbles

Question 18

what is the purpose of cell fractionation?

Answer 18

used to separate organelles

Question 19

what is homogenisation?

Answer 19

breaking up the cell

Question 20

what is the process for homogenisation?

Answer 20

vibrate or grind cells
this breaks up the plasma membrane and releases organelles into solution
solution should be ice cold, isotonic and buffered

Question 21

why should the solution be ice cold?

Answer 21

reduces enzyme activity which could break down organelles

Question 22

why should the solution be isotonic?

Answer 22

prevents damage to the cells by osmosis

Question 23

why should the solution be buffered?

Answer 23

maintains pH, which prevents damage to the cell

Question 24

what happens in filtration?

Answer 24

get rid of large cell debris by filtering through a gauze

Question 25

what happens in ultracentrifugation?

Answer 25

separating organelles

Question 26

what is the process of ultracentifugation?

Answer 26

cell fragments are poured into a tube
spun in a centrifuge
spun at a low speed
heaviest organelle are flung to the bottom
form a thick sediment= pellet
rest of organelles stay in the supernatant
spun at higher speeds

Question 27

what is the order organelles are separated in? (heaviest to lightest)

Answer 27

nuclei 
mitochondria
lysosomes 
endoplasmic reticulum 
ribosomes