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A-Level Biology Year 1 - OCR B notes > Chapter 1 - Cells and Microscopy > Flashcards

Chapter 1 - Cells and Microscopy Flashcards

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1
Q

What is the maximum magnification of a Light Microscope?

A

x1500

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2
Q

What is the resolution limit of a Light Microscope?

A

200nm

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3
Q

What is resolution?

A

The ability to distinguish between 2 separate points.

The limit of resolution = λ / 2

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4
Q

What is the resolution limit of a CLSM?

A

200nm

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5
Q

Advantages of Light Microscopes

A
  • Low skill set needed
  • Cheaper than other types
  • Can be transported to use in field work
  • Can observe living organisms
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6
Q

Disadvantages of Light Microscopes

A
  • Low resolution
  • Limited magnification
  • Many internal structures can’t be seen
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7
Q

How to prepare a temporary slide for observation using Light Microscope.

A
  1. Fixation - use 70% alcohol
  2. Staining - use a few drops of differential stain
  3. Mounting - cover with coverslip to exclude dust and air.
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8
Q

Advantages of temporary slides procedure

A
  • Rapid and Simple

- Can mount in glycerine to prolong examination period.

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9
Q

How to prepare a permanent slide for observation using Light Microscope

A
  1. Fixation - preserves specimen, minimises distortion, alcohol or acestic acid added.
  2. Dehydration - place in up to 70% alcohol.
  3. Clearing - addition of xylol
  4. Embedding - resin, plastic or wax
  5. Sectioning - use a microtome
  6. Differential staining - can be permanent or temporary.
  7. Mounting - embeds and protects material.
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10
Q

Different types of plant stain

A

Iodine - temporary, blue-black, starch

Aniline Sulfate - temporary, yellow, lignin

Eosin - permanent, red, cellulose

Toludine -permanent.
Red, lignin.
Purple, cellulose

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11
Q

Advantages of using differential stains

A
  • easier to observe tissues, cells and chemicals
  • allows to distinguish between different vessels in plants.
  • allows to distinguish between different types of white blood cells.
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12
Q

How to use Leishman’s stain

A
  1. Allow blood smear to airdry
  2. fix with methanol
  3. flood with leishman’s stain
  4. leave for 2 mins
  5. dilute with distilled water
  6. leave for 7-10 mins
  7. wash with distilled water until appears pale pink.
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13
Q

How to use Wright’s stain

A
  1. Allow blood smear to air dry
  2. flood with wright’s stain
  3. leave for 3-4 mins
  4. dilute with distilled water
  5. leave for 6-8 mins
  6. wash with distilled water or phosphate buffer until has pale pink edges
  7. air dry and mount
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14
Q

key points of cell theory

A
  • a cell is the basic unit of all life
  • all living organisms are made up of either one or more cells
  • metabolic processes occur in living cells
  • all new cells come from pre-existing cells
  • cells possess genetic material which is passed to daughter cells.
  • a cell is the smallest unit of life capable of surviving independently.
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15
Q

Advantages of electron microscopes

A
  • greater resolution
  • higher magnifications can be used
  • finer detail can be seen
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16
Q

Disadvantages of electron microscopes

A
  • specimen must be dead
  • highly expensive
  • high skill set required
  • must be used in specialized room
  • more complex process
  • more prone to artifacts
17
Q

Advantages of using a CLSM

A
  • ability to eliminate or reduce background information
  • high resolution
  • can obtain 3D reconstructions
  • can image living cells and tissues
  • any out of focus light is blocked
18
Q

How are fluorescent markers work?

A
  • fluorochromes attach to antibody that is specific for one antigen on or in the cell
  • can also be tagged to a chemical
  • each fluorochrome has its own peak excitation and emission wavelength
  • lasers with different wavelengths are used for different fluorochromes
  • laser excites the fluorochrome causing the tagged cells to fluoresce
  • fluorescence is counted by the detector
19
Q

What is the maximum resolution of an electron microscopes?

A

0.1nm

20
Q

What is the maximum resolution of a CLSM?

A

x2000

21
Q

How is the beam focused in a light microscope?

A

Condenser

22
Q

How is the beam focused in a CLSM?

A

Objective lens

23
Q

How is the beam focused in electron microscopes?

A

Electromagnets

24
Q

Maximum magnification of TEM?

A

x1,000,000

25
Q

What is the maximum magnification of an SEM?

A

x500,000

A-Level Biology Year 1 - OCR B notes (15 decks)

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