Search for notes by fellow students, in your own course and all over the country.
Browse our notes for titles which look like what you need, you can preview any of the notes via a sample of the contents. After you're happy these are the notes you're after simply pop them into your shopping cart.
Title: A level OCR A Cell structure
Description: Contains all the information on the specification for the topic- cell structure
Description: Contains all the information on the specification for the topic- cell structure
Document Preview
Extracts from the notes are below, to see the PDF you'll receive please use the links above
Cell Structure
•
•
Magnification: how many times bigger the image is produced
Resolution: ability to distinguish between 2 points that are close together as
separate structures
Optical microscopes:
•
•
•
•
•
•
Use light to form an image- limits the resolution of the microscope
Produce a colour image
Maximum resolution: 200nm
Can be used to observe eukaryotic cells (living or dead), their nuclei
and maybe mitochondria and chloroplast
Cant be used to observe smaller organelles i
...
ribosomes, ER or
lysosomes
Maximum magnification: x1500
Electron microscopes:
•
•
•
•
•
•
Uses electrons to form an image
Vacuum needed for electron microscopes
Maximum resolution: 0
...
5nm
• Allows internal structures within cells to be seen
▪ Disadvantages:
• Can only be used with very thin specimens
• Cannot be used to observe live specimens
• Lengthy treatment to prepare specimens
• Don’t produce a colour image
o SEM: electrons scanned across the surface of the specimen
...
• A laser scanning confocal microscope moves a single
spot of focused light across a specimen (point
illumination)- causes fluorescence from the components
with dye
• Emitted light from the specimen is filtered through a
pinhole aperture
...
Dry mount: specimens viewed whole or cut into very thin slices with a sharp bladesectioning
Specimen is placed on the centre of the slide and a cover slip is placed over the
sample
2
...
Squash slide: wet mount is first prepared, then a lens tissue is used to gently press
down the coverslip
Potential damage to a coverslip can be avoided by squashing the sample inbetween
two microscopic slides
4
Title: A level OCR A Cell structure
Description: Contains all the information on the specification for the topic- cell structure
Description: Contains all the information on the specification for the topic- cell structure