TESTS FOR BIOLOGICAL MOLECULES Flashcards
Test for starch
Few drops of iodine solution (potassium iodine and iodine)
Yellow brown-purple black
Starch, amylose and amylopectin
Blue/black = starch
Deep blue= amylose
Red/purple =amylopectin
Reducing sugars test
All monosaccharides and some disacchardies
Donate electrons
use benedicts reagent ( copper 2 sulphate)
Heat Benedict reagent
Reducing sugars react with copper ions
result in addition of electrons to blue cu2+ ions
Reducing them to brick red Cu+
More reducing sugar= more precipitate = less blue cu2+
Non reducing sugars
Dont react with Benedict
e..g Sucrose
Add dilute Hcl and heat, then add BR
Sucrose - hydrolysed by acid to glucose and fructose which ARE reducing
Colourimetry
Carbohydrate quantitative test
Measures absorbance/transmission of light by a coloured solution
More concentrated = more light absorbed/less transmitted
Emulsion test
Lipids
ethanol and water
White emulsion = lipid
Biosensors
Use biological components to determine presence of biological molecules e.g. glucose
Molecular recognition protein/DNA immobilised to surface, interacts with molecule
Transaction- interaction produces change in transducer, response e.g.. dye
Display - visible qualitative/quantitative signal e..g colour and reading
Protein test
Biruret reagent ( alkali and copper sulphate - NaOH) Blue - copper 2 sulpahte Protein = purple
Chromatography
Separating mixtures of substance sthat are soluble in same solvnet
Spot of mixture of some paper
Separated - more soluble spread faster
Rf= distance moved by spot/solvent
Tlc
Stationary phase= silica el on surface
AA added to one end( submerged in organic solvent)
Organic solvent moves through
Rate which they move through - interactive ( H bonds) they have with the silica in stationary phase = different AA move different distances at same time
