2.1.2 Slides and photomicrographs Flashcards
how can you view specimen without staining?
adjusting the iris diaphragm or use a dark background
what does acetic orcein bind to?
DNA
what does acetic orcein stain?
chromosomes dark red
what does eosin bind to?
cytoplasm
what colour is eosin?
red
what does Sudan red stain?
lipids
what does iodine stain?
iodine in potassium iodine solution stains the cellulose in plant cell walls and starch granules
what colour does iodine stain cellulose?
yellow
what colour does iodine stain starch granules?
blue/black (will look violet under the microscope)
what is methylene blue?
an all purpose blue stain
how are slides prepared by experts in a lab?
-dehydrating the specimen
-embedding them in wax to prevent distortion whilst slicing
-using a special instrument to make sections (which are stained and mounted in a special chemical to preserve them)
how to find the actual size of the structures? eg a leaf in a transverse section
-measure the widest part of the leaf on the photomicrograph, in mm
-convert that measurement to µm, by multiplying by 1000x
-now divide this figure by the magnification (actual thickness of the leaf)
-use IAM formula to find magnification, if image is given
how to draw a biological drawing?
-use plain paper
-use a sharp pencil for both drawings and labels
-include a title and the magnification used
-indicate the scale
what is differential staining?
specimens or sections are sometimes stained with multiple dyes to ensure the different tissues within the specimen show up
what makes the structures within the specimen that have absorbed the dye visible?
the dyes used absorb specific colours of light while reflecting others
