Cells AQA AS Biology PART 3 of 6 TOPICS: Methods for studying cells

A quick summary on optical, tramission electron and scanning electron microscope and their pros and cons

It also includes cell fractionation

Based on AQA spec

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Preview of Cells AQA AS Biology PART 3 of 6 TOPICS: Methods for studying cells

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Cells (AQA AS Biology) PART 3 of 6 TOPICS
Methods of studying cells:
Optical microscopes
Cheaper than electron microscopes
Magnification and resolution is not as electron microscopes
Transmission electron microscopes
Smaller wavelength of electron beam allows organelles
smaller than mitochondria to be seen
Specimen has to be dead
Scanning electron microscopes
Gives 3D structure of organelles
It is very expensive
Cell fractionation has three processes:
1. Homogenisation is where the cell membrane is broken to release the organelles into an ice
cold (preventing enzyme activity), isotonic (preventing shrivelling and bursting of organelles)
buffer (to keep the pH constant to prevent the enzymes and organelles from denaturing).
2. Filtration is where the cell membrane is separated from the organelles as well as large debris
using a gauze.

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Ultracentrifugation is where the organelles are separated from each other. All the organelles
are poured into a tube and centrifuged where it is spun at high speed at an angle. Heaviest
organelles such as nuclei form a pellet at the bottom with all the lighter organelles at the top
called the supernatant.…read more


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