Flashcards in 1: Electron Microscopes and Ultrastructure Deck (15):
1. is the ability of the microscope to show two close objects separately in the image
How do you know when the resolution of the microscope has been exceeded?
1. the point above which the image can no longer be focused sharply
What does resolution depend on?
1. the wavelength of the rays used to form the image
2. the shorter the wavelength, the higher the resolution
What has a shorter wavelength: electrons or light? What does this mean for microscopes?
2. electron microscopes have a higher resolution than light microscopes
3. they can therefore produce a sharper image at much higher magnifications
What is the resolution in a light microscope and electron microscope, respectively?
1. light: 0.25 um
2. electron: 0.25 nm
What is the maximum magnification in a light microscope and electron microscope, respectively?
1. light: x500
2. electron: x500,000
Name two types of electron microscope and their uses.
1. Transmission electron microscope (TEM): used to view ultra-thin sections
2. Scanning electron microscope (SEM): produce an image of the surfaces of structures
Draw and label a scanning electron microscope (SEM). (p5)
1. voltage feed
2. electron gun
4. electron beam
7. objective lens
8. intermediate lens
9. projector lens
10. viewing port
11. fluorescent screen
There is an important trend in science related to technology and discovery. What is it? Give an example.
1. improvements in technology or apparatus lead to developments in scientific research
2. invention of the electron microscope led to a much greater understanding of the structure of cells known as the ultrastructure
You need to be able to recognise different ultracellular components of a cell, and label a micrograph. This needs exam question practice and knowledge of the ultrastructure of eukaryotic cells (next deck).
They may also ask you to "deduce the function of the specialised cell" e.g. chloroplasts + large vacuole so function = photosynthesis"
What do chloroplasts do?
1. carry out photosynthesis
What does the cell wall do?
1. supports and protects the cell
What does the plasma membrane do?
1. controls entry and exit of substances
What do the (free) ribosomes do?
1. synthesize cytoplasmic proteins