Analysis Pf Cell Components

Question 1

What is magnification?

Answer 1

How much bigger the image is that the specimen

Question 2

How do you calculate magnification?

Answer 2

by dividing the size of the image you see by the size of the real object.

You need to make sure all distances are in the same unit in this calculation.

Question 3

To convert a millimetre (mm) to a micro metre (um) you times by which value?

Answer 3

X1000

Question 4

To convert micrometres (um) to nanometres (nm) you times by which value?

Answer 4

X1000

Question 5

What is Resolution?

Answer 5

how detailed an image s . more specifically it is how well a microscope distinguishes between two pints which are close together on a specimen. If a microscope cant separate two objects then increasing magnification won’t help.

Question 6

What are the two types of microscope ?

Answer 6

Optical (light) microscopes
Electron microscope

Question 7

What does an optical microscope use to form an image?

Answer 7

uses light to form an image. Light has quite a long wavelength which means the resolution of a light microscope is smaller as its harder to distinguish between two points.

Question 8

Generally what is the highest magnification of an optical microscope?

Answer 8

X1500

Question 9

Generally what is the maximum resolution of an optical microscope?

Answer 9

0.2 um

Question 10

Due to a lack of resolution some organelles cant be seen by an optical microscope , name some of these organelles:

Answer 10

Ribosomes
The rough endoplasmic reticulum
The smooth endoplasmic reticulum
Lysosmes

Question 11

What does an electron microscope use to form an image?

Answer 11

uses electrons form an image. Electrons have tiny wavelengths so give the microscope high resolutions as its easy to distinguish between two points.

Question 12

Generally what is the greatest magnification of an electron microscope?

Answer 12

x1500 000

Question 13

Generally what is the maximum resolution of an electron microscope?

Answer 13

0.0002 um

Question 14

There are two types of electron microscope name these two types.

Answer 14

Transmissions electron microscope (TEM)

Scanning electron microscope (SEM)

Question 15

How does a transmissions electron microscope work?

Answer 15

TEMs use electromagnets to focus a beam of electrons , this beam of electrons is then transmitted through the specimen being viewed.

Denser parts of the specimen absorb more electrons so the image produced shows these parts in a darker colour.

Question 16

Why can you not look at living organisms in a transmissions electron microscope?

Answer 16

you must look at the specimen in a vacuum , also the specimen must be sliced very thinly.

Question 17

How does a scanning electron microscope work?

Answer 17

A SEM scans a beam of electrons across a specimen, it can in doing this produce a 3D image of the cell surface, this image is not viewed through a lens it is viewed on a computer screen

Question 18

How are some images from an electron microscope coloured?

Answer 18

she images may be coloured on a computer after the image has been produced by the electron microscope.

Question 19

What is the difference between the specimens that can be viewed under a TEM and a SEM?

Answer 19

TEMs fan only be used on non living specimens as they’re viewed in a vacuum, and can only be thin

Question 20

What type of slide do you use to look at a sample under a optical microscope?

Answer 20

Microscope

Question 21

How do you prepare a temporary mount?

Answer 21

1. Start by pipetting a small drop of water onto the centre of the slide.
2. Then use tweezers to place a thin section of your specimen on top of the water drop. (Your specimen needs to let light through it for you to be able to see it clearly under the microscope — so if you’ve got quite a thick specimen, you’ll need to take a thin slice to use on your slide).
3. Add a drop of a stain. Stains are used to highlight objects in a cell.
4. Finally, add the cover slip (a square of clear glass or plastic that protects the specimen). To do so, stand the slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles under there they’ll obstruct your view of the specimen

Question 22

Why are temporary mounts called temporary mounts?

Answer 22

They cant be stored very long.

Question 23

What is a microscope artefact?

Answer 23

Things you can see down a microscope that aren’t part of the cell or specimen you’re looking at.

Question 24

Are artefacts more common in electron microscopes or optical microscopes?

Answer 24

Artefacts are especially common in electron micrographs because specimens need a lot of preparation before you can view them under an electron microscope.

Question 25

If you wanted too look at some cells under an electron microscope you would need to first separate them from the rest of the cell , by which process can you separate organelle from the rest of the cell?

Answer 25

Cell fractionation

Question 26

What is homogenisation ?

Answer 26

breaking up the cells

Question 27

Name ways in which cells can be homogenised

Answer 27

Eg by vibrating the cells or grinding them in a blender

Question 28

Why must the solution the homogenate is contained within be kept ice cold?

Answer 28

to reduce the activity of enzymes that break down organelles

Question 29

The solution the homogenate is contained within must also be isotonic why is this?

Answer 29

it should have the same concentration of chemicals as the cells being broken down, to prevent damage to the organelles through osmosis

Question 30

The solution that the homogenate is contained in must also be buffered by a pH buffer , why is this ?

Answer 30

To maintain the pH

Question 31

What type of solution should a homogenate be placed in?

Answer 31

Buffer

Question 32

What happens in the filtration stage of cell fractionation ?

Answer 32

Getting rid of the big bits

Question 33

Why is the homogenate solution filtered?

Answer 33

to separate any large cell debris or tissue debris, like connective tissue, from the organelles. The organelles are much smaller than the debris, so they pass through the gauze.

Question 34

Why do scientist homogenise the cells?

Answer 34

To break up plasma membrane and release the organelles into solution

Question 35

After filtration in cell fractionation what remains?

Answer 35

you're left with a solution containing a mixture of organelles. To separate a particular organelle from all the others you use ultracentrifugation

Question 36

What machine is used in cell fractionation?

Answer 36

Centrifuge

Question 37

What are the steps in ultracentrifugation?

Answer 37

1. The cell fragments are poured into a tube. The tube is put into a centrifuge (a machine that separates material by spinning) and is spun at a low speed. The heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge. They form a thick sediment at the bottom — the pellet. The rest of the organelles stay suspended in the fluid above the sediment — the supernatant. 2. The supernatant is drained off, poured into another tube, and spun in the centrifuge at a higher speed. Again, the heaviest organelles form a pellet at the bottom of the tube. The supernatant containing the rest of the organelles is drained off and spun in the centrifuge at an even higher speed. 3. This process is repeated at higher and higher speeds, until all the organelles are separated out — see Figure 9. Each time, the pellet at the bottom of the tube is made up of lighter and lighter organelles.

Question 38

What is a the supernatant?

Answer 38

The liquid layer that results from centrifugation of a mixture of liquid and solids

Question 39

which organelles deposit first when spun in a centrifuge?

Answer 39

Heaviest

Question 40

Which organelles may be found in the first pellet created in ultracentrifugation?

Answer 40

Nuclei and chloroplasts

Question 41

Which organelles may be found in the second pellet created in ultracentrifugation?

Answer 41

Mitochondria and lysosomes

Question 42

Which organelles may be found in the third pellet created in ultracentrifugation?

Answer 42

ER and ribosomes

Question 43

Way to remember order of organelles

Answer 43

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