Biological molecules

• Carbohydrates


  Chemical elements present: Carbon, hydrogen, oxygen (C,H,O)
• Lipids


  Chemical elements present: Carbon, hydrogen, oxygen (C,H,O)
• Proteins


  Chemical elements present: Carbon, hydrogen, oxygen, nitrogen, sulfur (C,H,O,N,S)
• Starch and glycogen


  Smaller molecules they are made from: Glucose
• Cellulose


  Smaller molecule it is made from: Glucose
• Proteins


  Smaller molecules they are made from: Amino acids
• Fats and oils


  Smaller molecules they are made from: Fatty acids, Glycerol
• Test for starch


  Add iodine to the sample
• Positive test for starch


  The yellow/brown solution turns blue/black
• Test for reducing sugars

  1. Add a few drops of Benedict's solution

  2. Warm in a water bath for 3 minutes at about 80 degrees
• Positive test for reducing sugars

  The more reducing sugar present, the closer to red the colour is
• Test for proteins


  Add equal volumes of Biuret A (copper sulfate) and Biuret B (sodium hydroxide) to the sample and shake
• Positive test for protein

  The solution turns from blue to purple
• Test for lipids


  1. Add 2cm3 of ethanol to the sample

  2. Leave to dissolve

  3. Add 2cm3 of distilled water to the sample
• Positive test for lipids


  A cloudy white emulsion will form
• Test for Vitamin C

  Add DCPIP to the solution drop by drop until the solution permanently changes colour
• Positive test for Vitamin C

  The solution will turn the DCPIP from dark blue to colourless permanently
• How the sequence of amino acids affects the protein produced

  • The different amino acids and their structures can determine the shape, size, properties of the protein and how it folds in different ways
• Functions of proteins


  • Antibodies
  • Enzymes
• Structure of DNA


  • It is a polymer made of many nucleotide monomers
  • It is made of 2 strands in the shape of a double helix
  • Each strand contains bases (A, T, C, G)
  • The 2 strands are linked between the bases
• Bases in DNA


  • A
  • T
  • C
  • G
• How the bases in DNA pair up

  • A always pairs with T
  • C always pairs with G
• Use of water in the body


  Water is used as a solvent in the body
• Processes in which water is used as a solvent

  • Digestion
  • Excretion
  • Transport