the microscope in cell studies

Question 1

magnification =

Answer 1

how many times bigger the image is than the real life object

Question 2

resolution

Answer 2

ability to distinguish between objects that are close together

Question 3

light microscopes limitatiosn

Answer 3

large wavelength so it is impossible to resolve objects that are closer than half the wavelength of light (max resolution - 200nm)

Question 4

electron microscopes advantages

Answer 4

electrons have a smaller wavelength so a higher resolution can be achieved
maximum resolution of 0.2 nm

Question 5

tem advantages

Answer 5

high resolution
can see internal structures within cells

Question 6

how does tem work

Answer 6

electromagnets focus beam of electrons
beam of electrons is transmitted through the specimen
denser parts abosorb more electrons so denser parts appear darker and image can be observed

Question 7

how sem works

Answer 7

scan beam of electrons across specimen
beam bounces off specimen and electrons are detected , forming an image

Question 8

disadbantages of TEM

Answer 8

need very thin specimens
dead specimens
long treatment to prepare specimen so artefacts are conmmon
do not produce a colour image

Question 9

advantages of sem

Answer 9

3d specimens
allow external 3D structure of specimens to be observed

Question 10

disadvantages of sem

Answer 10

lower resolution than tem
cant have live specimen
do not produce a colour image

Question 11

standard measurements for IAM questions

Answer 11

micrometers (um)

Question 12

converting from 1m to 1 nm

Answer 12

1m x1000 1mm
1mm x 1000 1um
1um x1000 1nm

Question 13

homogenisation process

Answer 13

sample placed in cold isotonic buffer
then blended up to break plasma membrane and open up the cell

Question 14

why cold isotonic buffer

Answer 14

cold - reduce activity of enzymes so they do not break down organelles

isotonic - not affect the osmotic potential of organelles, so they dont burst or shrink

buffer - prevent organelle enzymes from denaturing

Question 15

filtration process

Answer 15

filter homogenate
breaks up large cell debris
leaving a filtrate of organelles

Question 16

ultracentrifugation process

Answer 16

filtrate (of organelles) is placed in a centrifuge and spun at a low speed

densest organelles will settle at the bottom, forming a pellet, the rest of organelles are in the supernatant (nuclei)

supernatant drained,
spun at medium speed. heavier organelles settle at bottom, of tube (mitochondria)

supernatant drained and spun at high speed to further seperate.

Question 17

order of mass of organelles

Answer 17

nucleus
chloroplasts
mitochondria
lysomes
endoplasmic reticulun
ribosomes

Question 18

reasons for artefacts

Answer 18

dust
air bubbles fingerprints