More microscopy- 2.3 (3) Flashcards
Module 2, Chapter 2, 2.3, Page 20 & 21
What is an artefact?
a visible structural detail caused by processing the specimen and not a feature of the specimen
In which two types of microscopes do artefacts appear in?
light microscopes and electron microscopy
The bubbles that get trapped under the cover slip as you prepare a slide…
for light microscopy are artefacts
What is inevitable when preparing specimens for electron microscopy?
the changes in the ultrastructure of cells during the processing that the samples must undergo
What are artefacts seen as? - the loss of…
continuity in membranes
What are artefacts seen as? - distortion of…
organelles
What are artefacts seen as? - empty spaces in the…
cytoplasm of cells
What does experience enable scientists to distinguish?
between a artefact and a true structure
What can cause much discussion and controversy?
identifying artefacts in microscopy preparation
What was mesosome given as a name to?
invaginations (inward foldings) of cell membranes that were observed
What were mesosomes observed using?
electron microscopes after bacterial specimens had been chemically fixed
Were mesosomes thought to be a normal structure, or organelle, found within prokaryotes?
yes
The large surface area of the folded membrane was considered to be an…
important site for the process of oxidative phosphorylation
When specimens were fixed by the more recently developed, non-chemical technique called cryofixation, the…
mesosomes were no longer visible
What is now widely thought of mesosomes?
majority of mesosomes observed are actually artefacts
What are mesosomes produced by?
chemicals used in the fixation process in electron microscopy preparation
Are there still a number of scientists who believe that some species of bacteria do have mesosomes as part of their normal structure?
yes
What makes it a good example of how the scientific community accepted an idea based on the evidence available at the time?
as techniques improved and more evidence became available, the collective knowledge and, understanding developed, and changed.
What can new evidence provide?
either further support for a theory or disprove an earlier theory
What is constantly developing?
scientific knowledge
What has also continued to develop?
light microscopy
What do some of the latest technology produce?
images that are very different from electron micrographs but are just as useful
What is the function of conventional optical microscopes?
they use visible light to illuminate specimens and a lens to produce a magnified image
In fluorescent microscopes, what is used to illuminate a specimen that has been treated with a fluorescent chemical / dye?
a higher light intensity
What is fluorescence?
it is the absorption and re-radiation of light
What is used to produce a magnified image in laser scanning confocal microscopy?
light of a longer wavelength and lower energy is emitted and used
What moves a single spot of focused light across a specimen?
a laser scanning confocal microscope
What does the movement of a single spot of focused light across a specimen cause?
fluorescence from the components labelled with a dye
What is the emitted light from the specimen filtered through?
a pinhole aperture
What is only detected?
light radiated from very close to the focal plane
What is the focal plane?
the distance that gives the sharpest focus
