2.1 Basic components of living Flashcards
What are the 2 lenses called on a compound light microscope?
Objective lens and eyepiece lens
What are the 4 types of sample preparation?
Dry mount
Wet mount
Squash slides
Smear slides
Name 2 positively charged dyes and what they are attracted to
Methylene blue and Crystal violet
attracted to negatively charged materials in the cytoplasm
Name 2 negatively charged dyes and what they are repelled by
Nigrosine and Congo red
repelled by the negatively charged cytosol
What happens to gram positive bacteria when stained with crystal violet?
The gram positive bacteria retain the pain and appear blue/purple under a microscope
What happens to gram negative bacteria when stained with crystal violet?
Gram negative bacteria lose the stain due to thinner cell walls. They are then stained with a counterstain, safranin dye which makes them appear red.
Which type of bacteria is susceptible to penicillin?
Gram positive - it inhibits the formation of cell walls
What are the 4 stages in the production of pre-prepared slides?
- Fixing
- Sectioning
- Staining
- Mounting
What are the rules for producing good scientific drawings?
- include a title
- state magnification
- use a sharp pencil
- use white unlined paper
- use as much paper as possible
- draw smooth continuous lines
- do not shade
- label lines should not cross and should be parallel to the top of the page and drawn with a ruler
How is magnification calculated?
Magnification (no units) = size of image/actual size
What is magnification?
How many times larger the image is than the actual size of the object being viewed
What is resolution?
the shortest distance between 2 objects that can be seen as separate objects
What is resolution limited by?
Diffraction
What is diffraction?
Diffraction is the tendency of light waves to spread as they pass close to physical structures
How can resolution be increased?
by using beams of electrons
What do you use to calibrate a light microscope?
an eyepiece graticule
Name 4 disadvantages of electron microscopy
- expensive
- can only be used inside a carefully controlled environment in a dedicated space
- specimens can be damaged by the electron beam
- problem with artefacts
What are the 2 types of electron microscope?
- Transmission electron microscope
- Scanning electron microscope
What is the difference between TEM and SEM?
In TEM a beam of electrons is transmitted through a specimen whereas in SEM a beam of electrons is sent across the surface of the specimen
How is a sample prepared for electron microscopes?
fixation using chemicals/freezing
staining with heavy metals
dehydration with solvents
Name 4 differences between light microscopes and electron microscopes
- light microscopes are inexpensive to buy and operate
- electron microscopes are large and need to be installed
- electron microscopes require complex sample preparation
- in light microscopy samples can be living or dead
What is an artefact?
A visible structural detail caused by processing the specimen and not a feature of the specimen
How does a laser scanning confocal microscope work?
It moves a single spot of focused light across a specimen which causes fluorescence from components labelled with a fluorescent dye. This emitted light is filtered through a pinhole aperture and is detected. A 2D image is produced.
Name a use of laser scanning confocal microscopy
used in the diagnosis of diseases
