4. Biological molecules

• Most of the molecules in living organisms

  • Carbohydrates
  • Proteins
  • Lipids
• These all contain carbon and so are described as organic molecules
• Chemical Elements Table
• Large Molecules


  Made from Smaller Molecules
• Carbohydrates


  Long chains of simple sugars
• Glucose


  A simple sugar (a monosaccharide)
• Glucose molecules joining together

  1. Maltose is formed (a disaccharide)

  2. Starch, glycogen or cellulose can form (a polysaccharide)
• Glycogen, cellulose and starch are all made from glucose molecules
• Fats (lipids)


  • Most fats in the body are made up of triglycerides
  • Their basic unit is 1 glycerol molecule chemically bonded to 3 fatty acid chains
  • The fatty acids vary in size and structure
  • Lipids are divided into fats (solids at room temperature) and oils (liquids at room temperature)
• Proteins

  • Long chains of amino acids
  • There are about 20 different amino acids
  • They all contain the same basic structure but the 'R' group is different for each one
  • When amino acids are joined together a protein is formed
  • The amino acids can be arranged in any order, resulting in hundreds of thousands of different proteins
  • Even a small difference in the order of the amino acids results in a different protein being formed
• chemical elements table

  
• 1 2

  
• amino acid

  
• amino acid to form protein

  
• Test for glucose (a reducing sugar)

  1. Add Benedict's solution into sample solution in test tube

  2. Heat at 60 - 70 °c in water bath for 5 minutes

  3. Take test tube out of water bath and observe the colour
• Positive test for glucose

  Colour change from blue to orange or brick red
• Test for starch using iodine


  Add drops of iodine solution to the food sample
• Positive test for starch

  Colour change from orange-brown to blue-black
• Test for protein

  Add drops of Biuret solution to the food sample
• Positive test for protein

  Colour change from blue to violet / purple
• Test for lipids

  1. Food sample is mixed with 2cm3 of ethanol and shaken

  2. The ethanol is added to an equal volume of cold water
• Positive test for lipids

  Cloudy emulsion forming
• Test for vitamin C

  1. Add 1cm3 of DCPIP solution to a test tube

  2. Add a small amount of food sample (as a solution)
• Positive test for vitamin C

  Blue colour of the dye disappearing
• benedicts test for glucose

  
• iodine test

  
• test for protein

  
• test for lipids

  
• test for vitamin c

  
• DNA

  Deoxyribonucleic acid, the molecule that contains the instructions for the growth and development of all organisms
• DNA molecule

  • Consists of two strands of DNA wound around each other in a double helix
• Nucleotides


  The individual units of DNA
• Components of a nucleotide

  • Phosphate
  • Deoxyribose sugar
  • Base
• DNA bases

  • Adenine (A)
  • Cytosine (C)
  • Thymine (T)
  • Guanine (G)
• Base pairing in DNA

  • Adenine always pairs with Thymine (A-T)
  • Cytosine always pairs with Guanine (C-G)
• DNA backbone

  The phosphate and sugar section of the nucleotides form the 'backbone' of the DNA strand (like the sides of a ladder)
• DNA rungs


  The base pairs of each strand connect to form the rungs of the ladder
• It is this sequence of bases that holds the code for the formation of proteins
• DNA, chromosome and the nucleus

  
• A nucleotide