biochemical tests

• benedict's test for reducing sugars:

  1. add benedict's reagent to a sample and heat it in a water bath
  2. if test + form a coloured precipitate
  3. higher the concentration the further the colour change goes
• test for non-reducing sugars :

  1. if test is - still could ne a non reducing sugar present, to test for non reducing sugars like sucrose you have to break them down into monosaccharides
  2. get a new sample and add dilute hydrochloric acid and heat in water bath
  3. neutralise with sodium hydrogen carbonate and carry out benedict's test
  4. if + coloured precipitate
  5. if - stay blue
• test for glucose: use test strips coated in reagent they change colour if glucose is present and can be compared to a chart
• test for starch: add iodine dissolved in potassium iodide solution

  • if starch is present browny-orange to dark, blue-black
  • if not it stays browny-orange
• test for proteins: biuret test

  1. solution needs to be alkaline so add a few drops of sodium hydroxide solution
  2. add some copper(ii) sulphate solution
  3. if protein is present- turns purple
  4. if not present - stay blue
• emulsion test for lipids :

  shake the test substance with ethanol for 1min then pour the solution into water

  • if lipid is present solution will turn milky
  • the more lipid the more noticeable it will be
  • if no protein solution will stay clear
• a colorimeter is a device that measures the strength of a coloured solution by how much light passes through it
• a colourimeter measures absorbance. the more concentrated the colour the higher the absorbance
• a biosensor is a device that uses a biological molecule, such as an enzyme to detect a chemical and it produces a signal which is converted into an electrical signal by a transducer the signal is then processed and can be used to work out other info