Chapter 2 - Basic components of living systems Flashcards
What are the 3 things stated in cell theory?
- both plant and animal tissue is composed of cells
- cells are the basic unit of all life
- cells only develop from existing cells.
Why is light microscopy important, even today?
- easily available
- relatively cheap
- can be used out in the field
- can be used to observe living organisms, as well as dead, prepared specimens.
What is the advantage of having 2 lenses (objective and eyepiece) on a compound light microscope?
- objective lens produces a magnified image, which is magnified again by the eyepiece lens.
- allows for much higher magnification
- reduced chromatic aberration.
What are the different ways for sample preparation?
- dry mount
- wet mount
- squash slides
- smear slides
What is the purpose of stains?
- to increase contrast between different components.
- Different cellular components take up stains to different degrees.
- allows the components to be visible, so that they can be identified.
Example of positively charged dyes?
- crystal violet
- methylene
Example of negatively charged dyes?
- nigrosin
- congo red
How are gram-positive bacteria and gram-negative bacteria distinguished?
- crystal violet is applied (positively charged dye)
- gram-positive bacteria retain the crystal violet stain and appear blue/purple under microscope.
- gram-negative bacteria have thinner cell walls and lose the stain.
- they are stained with safranin dye (counterstain).
- they will appear red
which type of bacteria are susceptible to penicillin?
- penicillin inhibits the formation of bacterial cell walls.
- gram-positive are susceptible.
- gram-negative have thinner cell walls, which are not susceptible.
what are the stages involved in the production of a microscope slide?
- fixing
- sectioning
- staining
- mounting
What are the rules for a good scientific drawing?
- include a title
- state the magnification
- use a pencil
- draw smooth, continuous lines
- do not shade
- ensure proportions are correct.
- label lines should not cross and should not have arrow heads.
- label lines should be parallel to the top of the page.
- label lines should be drawn with a ruler.
What is magnification?
Magnification is how many times larger the image is than the actual size of the object being viewed.
What is resolution?
Resolution is the ability to see individual objects as separate entities.
What is resolution limited by?
The diffraction of light as it passes through samples and lenses.
- If light reflected from individual structures overlap due to diffraction, this means that the structures are no longer seen as separate entities and detail is lost.
How can you increase resolution?
- instead of light in a light microscope,
- use beam of electrons with an electron microscope.
why?
- electron beams have a wavelength thousands of times shorter than light.
- objects that are smaller and closer together can be seen separately without diffraction blurring the image.
