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

Anatomy and Physiology25 CardsCreated about 1 month ago

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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TermDefinition
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
A M

I - image size
A - actual size
M - magnification

Eukaryotic Cells
Have a nucleus containing genetic info
Prokaryotic cells
Don’t have a nucleus | No membrane bound organelles