Cell Structure Flashcards
What is resolution?
The ability of an optical instrument to see or produce an image that shows final detail clearly.
optical microscopes
Use light Lower resolution Maximum resolution 0.2 micrometers Good for look at whole cells or tissue Maximum useful magnification of a light microscope about x1500
Disadvantages of optical microscopes?
Uses only optical light between 400 and 700 nm
Resolution limits magnification
Wave length of visible light ranges from 400 to 700 nm so structures closer than 200nm will appear as one objects
Ribosomes can’t be examined as they are too small
Stages of using microscope
Start by clipping slide containing specimen onto stage
Select lowest-powered lens
Use coarse adjustment knob to move objective lens down to just above slide
Look down eyepiece and adjustment knob until clear image
If you need to see slide with greater magnification swap higher-powered objective lens and refocus
Calculating magnification
Total magnification= magnifying power of objective lens x magnifying power of eyepiece lens
Details about laser scanning microscope
Use laser beams to scan specimen tagged with fluorescent dye
Laser causes dye to fluoresce give off light. Light focused through pinhole onto detector. Detector hooked up to computer generated image. Image can be 3D
Pinhole any out of focus is blocked so microscope produce a much clearer image than normal light microscope
Can be used to look at objects at different depths in thick specimens
Electron microscopes are
Large and expensive
Need great deal of skill and training to use
Transmission and scanning
Higher resolution
Transmission electron microscopes
Specimen have to be chemically fixed by dehydrated and stained
Beams of electrons passes through specimen stained by metal salts some electrons pass through and are focused on screen or photographic plate
Form 2D black and white images
Can produce up to 2 million times some even 50 million times
Scanning electron
Electrons bounce off specimen surface
3D image with magnification from 15 x to x 200000
Image black and white computer programme adds colour
Calculations
I/MA
Um to convert to x 1000
Graticules
Little thing used to measure under microscope
Nucleus
Has nuclear envelope with double membrane
Has nucleolus between envelope and nucleus
Control centre of cell, contains instructions of cell
Rer/ ser
Rough endoplasmic reticulum- Coated with ribosomes, provides area to assemble amino acids into proteins
Smooth endoplasmic reticulum- no ribosomes, catalyse reactions involved in lipid metabolism
Golgi appartus
Membrane bound sacs
Protein modifying
Mitochrondrion
Site of ATP production during aerobic respiration
Self replicating abudent to in cells
