3.2.1.3 studying cells

Question 1

what is the definition of magnification?

Answer 1

how many times bigger an object appears.

Question 2

what is the definition of resolution?

Answer 2

ability to distinguish between two points = how close together two points can be and still be seen as separate points.
shorter wavelength = greater resolution.

Question 3

what max magnification does a light microscope produce?

Answer 3

2000 x

Question 4

what max magnification does a transmission/ scanning electron microscope produce?

Answer 4

10,000,000 x

Question 5

what is the max resolution of a light microscope?

Answer 5

200nm

Question 6

what is the max resolution of a transmission electron microscope?

Answer 6

0.1nm

Question 7

what is the max resolution of a scanning electron microscope?

Answer 7

20nm

Question 8

how does a light microscope illuminate the sample and focus the waves?

Answer 8

using light and lenses.

Question 9

how does a TEM and SEM illuminate the sample and focus the waves?

Answer 9

using electrons and electromagnets.

Question 10

how do you prepare a specimen when using the light microscope?

Answer 10

• can be living cells.
• thin specimens on cover slips.
• potential staining needed.

Question 11

how do you prepare a specimen when using TEM and SEM?

Answer 11

• cannot be living.
  1. placed in a vacuum.
  2. fixed.
  3. dehydrated.
  4. stained using metal salts.
  5. mounted on a copper grid.

Question 12

how does staining with metal salts work?

Answer 12

• electrons scatter differently giving contrast.

Question 13

what is the advantages and disadvantages of light microscopes?

Answer 13

ADV = cheap.
DIS = low resolution and staining needed for non coloured specimens.

Question 14

what is the advantages and disadvantages of TEMs?

Answer 14

ADV = high resolution and magnification.
DIS = specimen is dead, large equipment, training needed, vacuum needed, complex staining process, electrons may destroy specimen, specimen must be very thin.

Question 15

what are the advantages and disadvantages of SEMs?

Answer 15

ADV = high resolution and magnification, gives 3D image.
DIS = specimen is dead, large equipment, training needed, vacuum needed, complex staining process, electrons may destroy specimen.

Question 16

what is the equation linked magnification, image size and actual size?

Answer 16

mag = image size / actual size

Question 17

how do you work out total magnification?

Answer 17

total mag = objective lens x eyepiece lens

Question 18

what is the power of G, giga?

Answer 18

10^9

Question 19

what is the power of M, mega?

Answer 19

10^6

Question 20

what is the power of k, kilo?

Answer 20

10^3

Question 21

what is the power of d, deci?

Answer 21

10^-1

Question 22

what is the power of c, centi>

Answer 22

10^-2

Question 23

what is the power of m, milli?

Answer 23

10^-3

Question 24

what is the power of µ, micro?

Answer 24

10^-6

Question 25

what is the power of n, nano?

Answer 25

10^-9

Question 26

what is the process to fraction cells?

Answer 26

1. cells undergo homogenisation to break open cells = releasing organelles from cells and producing the homogenate fluid.
2. ultra filtrate the homogenate to remove debris and whole cells.
3. centrifuge at low speeds to separate cell fragments and heavy organelles (nucleus is heaviest then chloroplasts and mitochondria etc)
4. resin the supernatant after you have removed pellet at higher speeds to get smaller organelles.

Question 27

when undergoing cell fractionation what must you keep the same?

Answer 27

1. keep cells COLD to reduce damage to organelles, slow down activity and stop digestion.
2. use PH BUFFER to keep pH the same to prevent enzyme denaturation.
3. use ISOTONIC SOLUTION (same water potential) to prevent damage to organelles by osmosis, stop cells bursting.