Testing for chemicals, microscopy

Test for reducing sugars

Benedict’s test

• add benedict’s solution (blue)

• boil in water bath

• positive = brick red + red brown precipitate

Test for protein

Biuret reagent

sodium hydroxide + copper sulfate = biurets reagent - light blue

positive = mauve (purple)

Test for lipids

• add ethanol

• mix vigorously

• add water

• positive = white emulsion / suspension. NOT precipitate

Test for starch

• a few drops of iodine

• positive = blue black

Emulsion

2 solutions that are mixed but don’t form a single layer

Precipitate

a solid suspended in liquid

Reducing sugar and (4) examples

loses electrons

eg, glucose, fructose, lactose, maltose

Equation for actual size of specimen under microscope

Image size = actual size x magnification

conversion factor (micrometers)

( no. if divisions on stage micrometer x length of division (micrometers ) ) / no. of decision on eye piece graticule

steps for observing prepared specimen under microscope (6)

1. clip slide to stage

2. select lowest power objective lens

3. use coarse adjustment knob to bring stage up to just below objective lens

4. look down eyepiece and use coarse adjustment knob to move stage down until image is roughly in focus

5. adjust focus with fine adjustment knob until you get a clear image

6. if a greater magnification is required, focus using high powered objective lens