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2.1.2 Biological Molecules (Chemical Tests) (Benedicts Test (Reducing (all…
2.1.2 Biological Molecules (Chemical Tests)
Biuret Test
Proteins
and Biurets reagent to solution
if protein is present colour will change from blue to lilac
Benedicts Test
Reducing (all monosaccharides, and some disaccharides) and Non-Reducing Sugars
heat solution with Benedicts solution
if reducing sugar is present, solution will go from blue to green, to yellow, to orange/red (warmer colour means more reducing sugar present)
for non-reducing sugar: first check that there are no reducing sugars using Benedicts solution
boil solution with hydrochloric acid to hydrolyse and break glycosidic bonds
neutralise solution with sodium hydrogen carbonate and check with benedicts solution again
Reagent Test Strips
Reducing Sugars
dip strip into solution and compare colour with calibration card suplied
Iodine Test
Starch
add iodine to solution
if iodine is present then colour change from yellow-brown to blue-black
Emulsion Test
Lipids
mix solution with ethanol; lipids will dissolve
mix solution with water; lipids will not dissolve, and forms a cloudy white emulsion
Biosensors
convert biological or chemical variable into an electrical signal
Uses: detect contaminants in water; detect airborne bacteria
Chromatography
Stationary Phase: chromatography paper or thin-layer chromatography plate
Mobile Phase: solvent for the biological molecules e.g. water for polar molecules, and ethanol for non-polar molecules
Solvent travels up paper and carries constituents with it; different constituents have different levels of solubility, so are separated
Uses: urine testing in athletes for illegal drugs
Rf value can be calculated:
Calorimetry
works by passing light through a sample, and detecting how much of it is transmitted/ absorbed
create a calibration curve
Sammer Sheikh