biology - microscopy Flashcards
how to prepare a microscope slide using onion tissue?
1) peel off the epidermal layer using forceps
2) place the sample on a drop of water on a slide
3) add a few drops of iodine solution to sample
4) lower cover slip onto sample using mounting needle
why is a thin sample of tissue needed?
allows light to pass through so that internal structures can be seen
why is water added to the slide before adding the sample?
allows the sample to be suspended between the slide and cover slip, and ensures slip stays in place
why is iodine solution added to stain the cells?
iodine solution adds contrast as it reacts with starch in plant cells and turns blue-black (allows internal structures to be more visible)
why is the cover slip lowered using a mounting needle?
ensure that no air bubbles get trapped
how to measure the length of a cell under a microscope?
measure using eyepiece graticule and calibrate with stage micrometer
how do you calculate the magnification?
magnification = observed cell length / actual cell length
what safety precautions are required?
eye irritation - wear goggles when handling iodine solution
cuts or injuries- place forceps out of the way not in use
