2.1- Slides and photomicrographs Flashcards
What type of specimens can be viewed using an optical microscope?
- Living organisms such as paramecium and amoeba
- Smear preparations of human blood and cheek cells
- Thin sections of animal, plant and fungal tissue, such as bone, muscle, leaf, root or fungal hyphae
How do you observe unstained specimens?
Many biological structures, including single celled organisms such as Paramecium, are colourless and transparent. Some microscopes use light interference rather than light absorption, in order to produce a clear image without staining. Some use a dark background against which the illuminated specimen shows up. These microscopes are particular useful for studying living specimens.
How can you view a living specimen by using a school microscope?
You can observe specimens with a school light microscope by adjusting the iris diaphragm to reduce the illumination of the specimen.
What is a stain?
Stains are coloured chemicals that bind to molecules in or on the specimen, making the specimen easy to see.
What is methylene blue?
It is an all purpose stain
How can certain structures of a cell be easily viewed?
Some stains bind to specific cell structures, staining each structure differently so the structure can be easily identified within a single preparation. This is called differential staining.
What does the Acetic orcein stain do?
- Binds to DNA and stains chromosomes dark red
What does the Eosin stain do?
-Stains cytoplasm;
What does the iodide stain do?
-Iodide in potassium iodide solution stains the cellulose in plant cell walls yellow, and starch granules blue/black (these will look violet under the microscope)
How have slides been prepared in laboratories?
- Specimens has been dehydrated
- Then embedded in wax to prevent distortion during slicing
- Finally, they use a special instrument to make very thin slices called sections- these are stained and mounted in a special chemical to preserve them.
What are some key points when using calculations involving magnification?
- Make sure to measure the image correctly
- Always check if anything needs to be converted
- Remember there are no units for magnification its just * number
How do you make drawings of slides?
1) Use a prepared slide such as a transverse section through a dicot leaf. Set it up on the microscope. Focus the specimen on a lower power.
2) Use a sharp HB pencil
3) Use a title that explains exactly what the drawing is and the magnification used
4) Indicate the scale- how much bigger your drawing is than the size of the image
5) Make sure your image is clear and detailed showing where different tissues areas are. Use clear unbroken lines and do not shade.
6) Label the areas shown
7) Make sure the specimen is directly over the hole in the microscope
8) Magnify the specimen
9) Use the fine focus knob to bring the specimen in focus
What does the sudan red stain do?
Sudan red stains lipids
