tests for molecules/qualitative methods

test for reducing sugars

warm with benedicts reagent

* reducing sugars turn from blue to brick red precipitate
* non reducing sugars stay blue

test for lipids

add water and ethanol then shake

* if lipid, white emulsion forms

test for protein

add biuret reagent

* proteins will change colour from blue to lilac/purple

test for starch

add few drops of iodine solution

* colour change from orange to blue black

test for non reducing sugars

boil with HCl then neutralise with NaCO3, then add benedicts solution and heat in a water bath

* non reducing sugars will change colour from blue to brick red precipitate

reagent test strips

test for the presence of reducing sugars such as glucose. using a colour coded chart the concentratino of sugar can be determined

colorimetry

used to qualititatively measure the absorbance or transmission of light by a coloured solution.

* the more concentrated the more light it will absorb and less will be transmitted

biosensors

uses biological components to determine the presence and concentration of molecules.

* molecular recognition: a protein or single stranded DNA is immobilised to the surface which interacts with the molecule under investigation
* transduction: causes chnge in transducer
* display: produces a visible signal such as particular colour on test strip or reading on machine

colorimetry method

* filter placed in colorimeter
* colorimeter calibrated using distilled water
* measure % transmittance using colorimeter
* plot calibration curve

paper & thin layer chromatography

separates the individual components in a mixture. the solubility of the solute in the solvent determines how far the molecule travels

Rf value

distance travelled by solute / distance travelled by solvent