2.1- 2.3 Microscopy Flashcards
(41 cards)
What is a microscope?
an instrument which enabes you to magnify an object hundreds, thousands and even hundreds of thousands of times
The first type of microscopes to be developed were?
light microscopes
When was light microscopes developed?
16th to 17th century
What does cell theory state?
1) both plant and animal tissue is composed of cells
2) cells are the basic unit of all life
3) cells only develop from existing cells
Advantages of light microscopes?
- easily available, relatively cheap
- used out in the field
- observe living organisms as well as dead, prepared speciments
a compound light microscope has two lenses. What are they
objective lens, placed near to specimen and eyepiece lens, through which the specimen is viewed
what do the objective and eyepiece lens do?
objective lens- produces a magnified image
eyepiece lens- magnifies it again by eyepiece lens
what does this objective/ eyepiece lens configuration allow?
allows for much higher magnification and reduced chromatic aberration than that in a simple light microscope
Illumination is provided where?
light underneath the sample
How may opaque specimens be illuminated
can be illuminated from above with some microscopes
What is the dry mount method of sample preparation
- sectioning (solid specimens are viewed whole/ cut into very think slices with a sharp blade)
- speciment placed on the centre of the slide and a cover slip is placed over sample
e. g. hair, polen and insect parts. Muscle tissue or plants can be sectioned and viewed in this way.
what is the squash slides method of sample preparation
-good technique for soft samples
-wet mount first prepared
-lens tissue is used to gently press down cover slip
-depends on material, potential damage to a cover strip can be avoided by squashing the sample between two microscope slides
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what is the smear slides method of sample preparation
-edge of a slide is used to smear the sample, creating a thin, even coating on another slide.
what is the wet mount sample preparation
- specimens suspended in a liquid such as water or an immersion oil
- cover slip placed on from an angle
what needs to be cared for in squash slides
cover slip is not broken when being pressed
what is an example of a smear slide?
sample of blood, good way to view the cells in the blood
wet mount method can be used for what method?
aquatic samples and other living organisms
what is necessary in scientific drawings
- a title
- magnification
- sharp pencil for drawings and labels
- white unlined paper
- use as much of paper as possible
- smooth continuous lines
- do not shade
- draw clearly defined structures
- ensure proportions are correct
- label lines should not cross and no arrow heads
- label lines should be parallel to the top of page and drawn with a ruler
What can differential staining do?
- distinguish between two types of organisms that would otherwise be hard to identify
- can also differentiate between different organelles of a single organism with a tissue sample
What is the Gram stain technique used for?
To separate bacteria into two groups, Gram-positive bacteria and Gram-negative bacteria
How is the gram stain method carried out?
Crystal violet is first applied to a bacterial specimen on a slide, then iodine, which fixes the dye. Slide is washed with alcohol
How do we tell which one in gram-negative bacteria and one is gram-positive bacteria?
Gram Stain technique- Gram positive bacteria retain the CRYSTAL VIOLET STAIN and will appear blue or purple under a microscope
Gram negative bacteria- thinner walls, and therefore LOSE THE STAIN
What happes after the gram-negative bacteria is identified by the gram stain technique?
They are then stained with safranin dye, which is called a counterstain. Bacteria will appear red
Gram-positive bacteria are susceptible to what?
antibiotic penicillion, which inhibits the formation of cell walls
