Biological Molecules

• Biochemistry


  The study of the chemicals and reactions that take place inside living things
• Biological molecules in our body


  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids
• Carbohydrates


  Organic molecules that contain carbon, hydrogen and oxygen
• Types of carbohydrate molecules


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides


  Single sugars (e.g. glucose, fructose, galactose)
• Disaccharides


  Double sugars made from two monosaccharides (e.g. maltose, sucrose, lactose)
• Polysaccharides


  Multiple sugars made from many monosaccharides linked by glycosidic bonds (e.g. starch, glycogen, cellulose, chitin)
• Functions of carbohydrates


  • Energy source
  • Building blocks of polysaccharides
  • Provide rigidity and shape to cells
  • Raw material for various products
• Benedict's test for glucose


  1. Add glucose/sweet food to Benedict's solution

  2. Heat the mixture

  3. Observe colour change
• Iodine test for starch


  1. Add iodine solution to starchy food

  2. Observe colour change
• Lipids


  Contain carbon, hydrogen, oxygen, and sometimes phosphorus or nitrogen
• Triglycerides


  Consist of glycerol and fatty acids, act as energy stores
• Types of triglycerides


  • Phospholipids
  • Cholesterol
  • Steroid hormones
  • Waxes
• Emulsion test for lipids


  1. Break food into pieces, mix with alcohol, shake

  2. Pour top layer, mix with water, shake

  
• Functions of lipids


  • Long-term energy storage
  • Provide protection
• Proteins


  Contain carbon, hydrogen, oxygen, nitrogen, and sometimes sulphur
• Amino acids


  Building blocks of proteins, linked by peptide bonds
• Biuret test for proteins


  1. Dissolve food sample, mix with Biuret solution

  2. Observe colour change
• Functions of proteins


  • Enzymes
  • Structural components (e.g. actin, myosin, collagen, keratin)
  • Hormones
• Nucleic acids


  Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus
• Types of nucleic acids


  • DNA (deoxyribonucleic acid)
  • RNA (ribonucleic acid)
• Nucleotide


  Building block of nucleic acids, consisting of a sugar group, a phosphate group, and a nitrogen-containing base
• DNA structure


  1. Nucleotides bind to form DNA strands

  2. Two parallel DNA strands form a double helix