Back to AI Flashcard MakerAnatomy and Physiology /OCR Biology A - 2.1.1 - Cell Structure Part 2
OCR Biology A - 2.1.1 - Cell Structure Part 2
This deck covers key concepts related to cell structure, focusing on microscopy techniques and cell types.
Compound microscopes
Use several lenses to obtain high magnification
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Key Terms
Term
Definition
Compound microscopes
Use several lenses to obtain high magnification
Resolution of light microscopy
About 200nm, which is good enough to see cells, but not details of cell organelles
Examples of procedures undertaken to prepare slide samples
Fixation
Dehydration
Embedding
Sectioning
Staining
Mounting
Light microscopy
Specimens are illuminated with light, which is focussed using glass lenses and viewed with the eye or photographic film.
Specimens can be living or de...
What is the wavelength of electrons
Less than 1nm, so can be used to resolve small sub-cellular ultra-structure
How did the electron microscope revolutionise biology
Allows organelles such as mitochondria, ER and membranes to be seen in detail for the first time
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| Term | Definition |
|---|---|
Compound microscopes | Use several lenses to obtain high magnification |
Resolution of light microscopy | About 200nm, which is good enough to see cells, but not details of cell organelles |
Examples of procedures undertaken to prepare slide samples | Fixation
Dehydration
Embedding
Sectioning
Staining
Mounting |
Light microscopy | Specimens are illuminated with light, which is focussed using glass lenses and viewed with the eye or photographic film.
Specimens can be living or dead, but often need to be stained with a coloured dye to make them visible |
What is the wavelength of electrons | Less than 1nm, so can be used to resolve small sub-cellular ultra-structure |
How did the electron microscope revolutionise biology | Allows organelles such as mitochondria, ER and membranes to be seen in detail for the first time |
Problems with an electron microscope | Specimens must be fixed in plastic and viewed in a vacuum, and must therefore be dead
Specimens can be damaged by the electron beam
Specimens must be stained with an electron-dense chemical (usually heavy metals like osmium, lead or gold) |
What are the two types of electron microscope | Transmission Electron Microscope (TEM)
| Scanning Electron Microscope (SEM) |
TEM | Works much like a light microscope, transmitting a beam of electrons through a thin specimen and then focusing the electrons to form an image on a screen or on film
Most common form of electron microscope and has best resolution |
SEM | Scans a fine beam of electron onto a specimen and collects the electrons scattered by the surface
Has poorer resolution but gives excellent 3D images |
Laser scanning confocal microscope | Used to observe an object at a certain depth within a cell |
Why do we stain samples | To ensure contrast between structures
| Identification of cells |
Magnification of light microscope | X1500 |
Magnification of TEM | X500,000 |
Resolution of TEM | 0.2 nm |
Magnification of SEM | X100,000 |
Resolution of SEM | 10nm |
Method of laser scanning confocal microscopy | Using a laser light to scan an object point by point and a computer assembles the image |
Pros of laser scanning confocal microscopy | Can be used to study whole, live specimens and can be used to obtain images at different depths in thick sections |
Main stains | Haemoxylin | Eosin |
Haemoxylin | Blue colour Stains DNA and RNA in all nuclei Often used together (differential staining) |
Eosin | Pink or red colour | Stains connective tissue and substances in cytoplasm |
IAM Equation | I I - image size |
Eukaryotic Cells | Have a nucleus containing genetic info |
Prokaryotic cells | Don’t have a nucleus
| No membrane bound organelles |