Biology 2:cells - cell fractioning and magnification

Question 1

whats the equation for actual size

Answer 1

image size = actual size x magnification

Question 2

how do you work out actual size ditrectly

Answer 2

use a stage micrometer and a eyepiece graticule(rulers)
work out how many mm 1 divisions using stage micrometer
use it directly to measure cell

Question 3

what’s the advantages of a scanning electromicroscope

Answer 3

3d surface image
high resolution and magnification

Question 4

disadvantages of SEM and TEM(6 THINGS)

Answer 4

no living tissues
no stains (artificial colour can be added)
high voltage(expensive/dangerous)
vacum(so air is not ionised) - difficult to maintain
expensive

Question 5

whats the advantages of Transmission microscopes

Answer 5

see inside organelles
high resolution and magnification

Question 6

what is cell fractioning

Answer 6

getting organelles out of cells

Question 7

name the 3 things that happen in cell fractioning

Answer 7

homogenize cells (break them apart)
differential centrifugation
results falling to the bottom of the tube (PELLet)

Question 8

during homogenization what does the solution need to be

Answer 8

cold
same water potential as tissue
buffer

Question 9

why does the solution need to be cold

Answer 9

to slow doen the enzymes released which could damage the organells

Question 10

why does the solution need to have the same water potential as the tissue

Answer 10

stops organelles bursting or shrinking due to osmosis

Question 11

why does the solution need to be a buffer

Answer 11

so ph doesn’t denature the proteins or affect the structure

Question 12

what happens during homegenization

Answer 12

tissue is cut up and ground up in a homogenizer to break open the cells
result is called the homegenate

Question 13

what happens in centrifugation

Answer 13

homegenate is put in centrifuge and spun