Analysis Of Cell Components

Question 1

How do you calculate magnification?

Answer 1

Size of image/size of real image

Question 2

How do you convert from mm to um to nm?

Answer 2

Mm to um (x1000)
Um to Nm (x1000)
Nm to um (/1000)
Um to mm (/1000)

Question 3

What is magnification?

Answer 3

How much bigger the image is than the specimen

Question 4

What is resolution?

Answer 4

How well a microscope distinguishes between 2 points that are close together

Question 5

Compare optical and electron microscopes:

Answer 5

Optical microscopes have a lower magnification (x1500) than electron (x1500000).

Optical microscopes have a lower resolution (0.2 um) than electron (0.0002 um).

Question 6

Give an advantage and disadvantage of TEMs:

Answer 6

High resolution images so show small objects.

Can only be used on thin specimens that are dead.

Question 7

Give an advantage and disadvantage of SEMs:

Answer 7

Can be used on thick specimens and can be 3D.

Give lower resolution images than TEMs and specimens must be dead.

Question 8

How do you prepare microscope slides?

Answer 8

1. Pipette a drop of water onto centre of slide.
2. Use tweezers to place a thin section of specimen on water.
3. Add stain.
4. Add cover slip.

Question 9

What is the first step of cell fractionation?

Answer 9

Homogenisation - breaking up cells. Vibrate cells or grind them in a blender which breaks the plasma membrane and releases the organelles into solution. It must be kept ice cold to reduce activity of enzymes that break down organelles. Must be isotonic to prevent damage via osmosis, and a buffer solution should be added to maintain the pH.

Question 10

What is the second step of cell fractionation?

Answer 10

Filtration - getting rid of the big bits. Solution is filtered through gauze to separate large debris from organelles. Organelles pass through.

Question 11

What is the third step of cell fractionation?

Answer 11

Ultracentrifugation - separating organelles.

1. Cell fragments poured into tube. Spun in centrifuge . Heaviest organelles flung to bottom, forming the pellet. Lighter organelles form supernatant.
2. Supernatant drained off and spun again. Heaviest organelles fall to bottom, process starts again.
3. Repeated at higher speeds until all organelles are separated out.

Question 12

What is the order that the organelles are separated?

Answer 12

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Nucleus, Chloroplasts, Mitochondria, Lysosomes, Endoplasmic Reticulum, Ribosomes