Microscopes Flashcards
What is the equation that links image size, magnification and real size?
Magnification= image size/ real size
Define magnification
how many times bigger the image is when compared to the object
Define resolution
minimum distance apart 2 objects can be to appear as separate items
What is the link between light and resolution
Longer wavelength than electrons so limited resolution
What is the limit of a light and electron microscope?
light= 0.2 micrometres
electron=0.1 nanomentres
What is the equation of the mitotic index?
number of dividing cells in field of view/ number of cells in total
Define cell fractionation
process where cells are broken up and the different organelles they contain are separated out
Describe homogenation
homogeniser breaks up cells to release the organelles
resultant fluid= homogenate
filter to remove debris and large cell chunks
Define ultracentrifugation
process by which the fragments in the filtered homogenate are separated in a machine called a centrifuge.
What speed are \_\_\_\_\_\_ spun at? Nuclei Lysosomes Chloroplast Mitochondria Ribosomes
nuclei= 1000
mitochondria= 3500
lysosomes= 16500
ribosomes=100,000
Name the two types of electron microscopes
Transmission electron microscope
Scanning electron microscope
What is the resolving power of the TEM and why is this not often achieved in practise?
0.1 nm
higher electron beam required which can destroy the specimen
difficulty in preparing the specimen
What are the main limitations of the TEM
specimen must be extremely thin
whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts
What are the main limitations of the TEM
specimen must be extremely thin
Image is 2D ( can build 3D via many images which is slow and complicated)
whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts
What are the limitations of the SEM?
whole system must be in a vacuum hence the specimen must be dead
complex staining process is required but image is not in colour
image may contain artefacts