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GMC > Cell theory & Microscopy > Flashcards

Cell theory & Microscopy Flashcards

1
Q

Who first discovered cells?

A

Robert Koch

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2
Q

What is cell theory?

A
  • All organisms composed of ONE OR MORE CELLS
  • Cells are the SMALLEST UNITS of life - form basis of organisation (in all living things)
  • Cells arise only by division of a PRE-EXISTING CELL
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3
Q

What can we do to understand a cells function?

A

Based on the COMPONENTS of the cell - VARIATION allows us to understand this

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4
Q

How many types of cells are in the human body?

A

At least 200 cell types

All have the same chromosomes

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5
Q

What is the Honey Fungus like?

A

Largest organism in the world (2,200 acres)

Probably <20 types of cells in this fungus

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6
Q

What is microscopy?

A

Produces enlarged image through magnification

Images can be sensor detected & computer manipulated/enhanced

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7
Q

What is resolution?

A

Ability to discriminate parts of an image

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8
Q

What are the two main types of microscopy used?

A

Light microscopy
Electron microscopy

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9
Q

What is light microscopy?

A
  • Broad beam of illuminating light focussed on specimen by condenser lens
  • Bright light passes thru img

Requires staining - often involves in cell death

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10
Q

What sort of section needs to be used for light microscopy?

A

Thin section

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11
Q

What is the limit of resolution and magnification for light microscopy?

A

Resolution = 0.2um

Which is 1000x

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12
Q

What are the 4 stages to prepare a section for light microscopy?

A
  1. Fixation
  2. Embed
  3. Section
  4. Staining
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13
Q

What is the purpose of fixation for light microscopy?

A

Stops the tissue falling apart, immobilises cells

(use fixative e.g. formaldehyde)

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14
Q

What is the purpose of embedding for light microscopy?

A

This provides mechanical support

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15
Q

What is the purpose of sectioning for light microscopy?

A

You need a thin section for light microscopy

Cut thin section using microtome (with metal, glass or diamond blade)

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16
Q

What is the purpose of staining for light microscopy?

A

Improves the visibility of the thin sections

17
Q

What is the equation for magnification?

A

Total magnification = magnification of objective lens X magnification of eyepiece lens

18
Q

What are the other types of light microscopy?

A
  1. Phase contrast
  2. DIC (Differential Interference Contrast)
  3. Fluorescence microscopy
  4. Laser scanning confocal light microscopy
19
Q

What is phase contrast microscopy?

A

Increase ‘contrast’ of images using phase contrast microscopy, cellular components have different refractive indexes

(good for looking at components)

20
Q

What is DIC microscopy?

A

Rates of change in refractive index = 3D shapes

(Differential Interference Contrast)

21
Q

What is fluorescence microscopy?

A

Specimen stained w fluorescent dye or protein - UV light excites the specimens, makes high contract img

Contrasts to dark background

22
Q

What protein is often used for fluorescence microscopy?

A

GFP from jellyfish (Green Fluorescent Protein)

23
Q

What is laser scanning confocal light microscopy?

A

Imagining of a thin plane with a thicker specimen (non-sectioned)

Focussed laser beam excited fluorescent molecules in cells & tissues, scans at single points in planes (gives sharp images)

24
Q

What is laser scanning confocal light microscopy useful for?

A

For living cells - can pool images to construct 3D model

25
Q

What are the two types of electron microscopy?

A
  1. Transmission electron microscopy (TEM)
  2. Scanning electron microscopy (SEM)
26
Q

How does electron microscopy work?

A

Uses a beam of electrons rather than light

Creates much more powerful images that light

26
Q

How does electron microscopy work?

A

Uses a beam of electrons rather than light

Creates much more powerful images that light

27
Q

How does TEM work?

A

Electrons pass through a very thin specimen - allows magnification of up to 1,000,000x

28
Q

How must the specimen be prepared for TEM?

A

Fixed, dehydrated, sectioned & stained with electron dense metals (platinum or gold)

29
Q

What happens to samples for TEM?

A

The samples could be rapidly frozen (cryofixatton)

Freeze-fracture reveals cell structure (knife used) cleaving cell then split surfaces using dense materials

30
Q

How does SEM work?

A

Electron beam is scanned over the surface - electrons bounce back & strike a detector

31
Q

What kind of image is produced by SEM?

A

Provides info on the surface details - appears 3D

Lower mag than TEM

32
Q

What are the 3 main recent advances in microscopy?

A
  • Cryo-electron microscopy
  • Super resolution microscorpy
  • Atomic force microscopy (AFM)
33
Q

What is Cryo-electron microscopy?

A

Less harsh method, more intricate detail

Use deep frozen molecules in solution & gentler electron beams (these are collected on the other side of the cell)

Determines structure of biomolecules

34
Q

What is super resolution microscopy?

A

Fluorescent based techniques

Overcomes traditional light resolution limit by various complex interference/tunneling methods

Allows resolution to ca. 100nm

35
Q

What is Atomic Force Microscopy (AFM)?

A

Method to visualise surfaces at a molecular scale

uses fine pointed tip linked to cantilever arm, can move up & down as moves across surface

Detect fine movement by reflected laser beam

GMC (6 decks)

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