Cell structure Flashcards
Advantages of light microscopes.
Cheap, easy to use, portable and able to study living organisms.
What is the magnification and resolution of light microscopes.
The magnification is up to x1500 and some types x2000. The resolution is limited as they cannot magnify higher while still giving a clear image.
Difference between magnification and resolution.
Magnification is how big an image appears to be in comparison with the original object and resolution is the ability to show fine detail clearly so that two parts of an image don’t merge.
How do light microscopes work?
Uses visible light of a wavelength between 400 and 700nm.
How do laser scanning microscopes work?
Uses laser light to scan an object and assemble the pixel information to form the image on a computer screen.
How do electron microscopes work.
Use a beam of fast-travelling electrons with a wavelength of about 0.004nm. The electrons are fired from a cathode, focused by magnets onto a screen.
Advantages of electron microscopes?
Produce highly magnified images. Much better resolution than optical microscope.
How do transmission electron microscopes work?
Specimen is dehydrated and stained. The beam of electrons which pass through are focused
What resolution and magnification can be achieved using a transmission electron microscope?
A 2D black and white image is formed. Can magnify up to x2 million times.
Difference between transmission electron microscope and scanning electron microscope.
Transmission electron microscope produces 2D images and electrons pass through the specimen whereas scanning electron microscope produces 3D images and electrons bounce off the specimens surface.
Magnification and resolution of scanning electron microscopes.
Magnification X15 to x200,000. Image is in black and white.
Why are specimens stained?
To make the specimen or part of the specimen easy to see.
Function of nucleus
Stores genetic information and provides instructions for protein synthesis
Function of nucleolus
Where ribosomes are made
Function of nuclear envelope
Separates the contents of the nucleus from the rest of the cell
Function of the rough endoplasmic reticulum
Channels for transporting substances around the cell. Gives surface area for ribosomes to assemble amino acids is into proteins