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Biology Topic 2 > Analysis Pf Cell Components > Flashcards

Analysis Pf Cell Components Flashcards

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1
Q

What is magnification?

A

How much bigger the image is that the specimen

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2
Q

How do you calculate magnification?

A

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.

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3
Q

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

A

X1000

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4
Q

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

A

X1000

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5
Q

What is Resolution?

A

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.

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6
Q

What are the two types of microscope ?

A

Optical (light) microscopes
Electron microscope

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7
Q

What does an optical microscope use to form an image?

A

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.

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8
Q

Generally what is the highest magnification of an optical microscope?

A

X1500

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9
Q

Generally what is the maximum resolution of an optical microscope?

A

0.2 um

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10
Q

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

A

Ribosomes
The rough endoplasmic reticulum
The smooth endoplasmic reticulum
Lysosmes

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11
Q

What does an electron microscope use to form an image?

A

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

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12
Q

Generally what is the greatest magnification of an electron microscope?

A

x1500 000

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13
Q

Generally what is the maximum resolution of an electron microscope?

A

0.0002 um

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14
Q

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

A

Transmissions electron microscope (TEM)

Scanning electron microscope (SEM)

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15
Q

How does a transmissions electron microscope work?

A

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.

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16
Q

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

A

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

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17
Q

How does a scanning electron microscope work?

A

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

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18
Q

How are some images from an electron microscope coloured?

A

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

19
Q

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

A

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

20
Q

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

A

Microscope

21
Q

How do you prepare a temporary mount?

A
  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
22
Q

Why are temporary mounts called temporary mounts?

A

They cant be stored very long.

23
Q

What is a microscope artefact?

A

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

24
Q

Are artefacts more common in electron microscopes or optical microscopes?

A

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

25
Q

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?

A

Cell fractionation

26
Q

What is homogenisation ?

A

breaking up the cells

27
Q

Name ways in which cells can be homogenised

A

Eg by vibrating the cells or grinding them in a blender

28
Q

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

A

to reduce the activity of enzymes that break down organelles

29
Q

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

A

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

30
Q

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

A

To maintain the pH

31
Q

What type of solution should a homogenate be placed in?

A

Buffer

32
Q

What happens in the filtration stage of cell fractionation ?

A

Getting rid of the big bits

33
Q

Why is the homogenate solution filtered?

A

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.

34
Q

Why do scientist homogenise the cells?

A

To break up plasma membrane and release the organelles into solution

35
Q

After filtration in cell fractionation what remains?

A

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

36
Q

What machine is used in cell fractionation?

A

Centrifuge

37
Q

What are the steps in ultracentrifugation?

A
  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.
38
Q

What is a the supernatant?

A

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

39
Q

which organelles deposit first when spun in a centrifuge?

A

Heaviest

40
Q

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

A

Nuclei and chloroplasts

41
Q

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

A

Mitochondria and lysosomes

42
Q

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

A

ER and ribosomes

43
Q

Way to remember order of organelles

A

Naughty clever monkeys like eating red raspberries

Biology Topic 2 (13 decks)

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