Biological molecules

Body mass

  • 65% of the body’s mass is oxygen

  • 18% of the body’s mass is carbon

  • 10% of the body’s mass is hydrogen


Carbohydrates

  • C,H,O arranged in a ring shape = simple sugar

  • Glucose is of simple sugar and is a monosaccharide

  • Disaccharide = simple sugars joined in a pair, e.g. sucrose

  • Polysaccharide = Large molecules of simple sugars, e.g. starch, glycogen and cellulose


Proteins

  • Consist of long chains of amino acids

  • 20 different amino acids joined in any order in animal and plant cells

  • There are structural proteins that form muscle, enzymes and some hormones


Lipids

  • Made of fatty acids and glycerol

  • Contain 3 fatty acids and 1 glycerol

  • Fats = solid at room temperature, oils = liquid at room temperature

  • They form cell membranes, steroid hormones and fats in storage cells


Tests

Starch

  • Drop a few drops of iodine / potassium iodide solution onto food on spotting tile or mix with solution

  • Brown → black-blue


Glucose

  • Add equal volume of pale blue Benedict’s solution to the sample and heat to 95C

  • Blue → Orange-red (considerable glucose), Yellow (moderate), Green (small)


Protein

  • Add 1cm3 of Biurettes solution to food sample

  • Blue → Purple


Lipid

  • Perform emulsion test

  • Add 4cm3 of ethanol to food sample, shake well and leave for one minute for solution to settle

  • Remove top part of filtrate and add to to test tube of water

  • Clear → Cloudy solution or layer