Chap 4

• Carbohydrates


  • Monosaccharides are single sugar molecules
  • Disaccharides are two sugar molecules linked
  • Polysaccharides are many sugar molecules linked
• Disaccharides


  • Maltose
• Main categories of molecules in living organisms

  • Carbohydrates
  • Fats
  • Proteins
• Fats or lipids


  • Large molecules made from fatty acids and glycerol
  • Fats that are liquids at room temperature are called oils
• Chemical elements present in carbohydrates, fats, and proteins

  • Carbon
  • Hydrogen
  • Oxygen
  • Nitrogen (only in proteins)
  • Small amounts of sulfur (only in proteins)
• Even a small difference in the order of amino acids

  Results in a different protein being formed
• Food tests

  Can be performed to identify starch, reducing sugars, proteins, fats and oils, or vitamin C
• Polysaccharides

  • Starch
  • Glycogen
  • Cellulose
• Test for starch


  Add drops of iodine solution to the food sample, color changes from orange-brown to blue-black if starch is present
• Proteins

  • Made of long chains of amino acids
  • About 20 different amino acids
  • Different combinations of amino acids result in hundreds of thousands of different proteins
• Monosaccharides

  • Glucose
• Organic molecules

  Molecules containing carbon, hydrogen, and oxygen
• The bodies of all living things are made of many different kinds of chemicals
• Formation of large molecules from smaller molecules

  Carbohydrates: Monosaccharides join to form disaccharides, which can further join to form polysaccharides
• Test for reducing sugars

  Add Benedict solution, heat, observe color change to identify reducing sugars
• Base pairs in DNA are held together by

  Hydrogen bonds
• Food test for proteins


  Add drops of buy red solution to the food sample, observe color change from Blue to Violet or purple
• Full names of bases are not required for exams, just the letters (A, T, C, G)
• Food test for fats and oils

  Mix food sample with two cubic centimeters of ethanol, add to cold distilled water, observe cloudy or milky Emulsion forming
• Chapter 4 Biological Molecules summary: Main topics include food tests for iodine, reducing sugars, proteins, fats and oils, vitamin C, and DNA structure
• Base pairs in DNA

  A pairs with T, C pairs with G
• Food test for reducing sugars

  Add Benedict solution into the food sample solution, heat at 60 to 70 degrees Celsius in a water bath for 5 minutes, observe color change from Blue to orange or brick red
• Food test for iodine


  Row color of iodine turns blue-black
• Food test for vitamin C

  Add 1 cubic centimeter of dcpip solution to a test tube, add a small amount of the food sample, observe blue color of the dye disappearing
• DNA or deoxyribonucleic acid contains the instructions for growth and development of all organisms
• DNA structure

  • Consists of two strands wound around each other in a double helix, strands contain bases (A, T, C, G), hydrogen bonds between pairs of bases hold the strands together, bases always pair up in the same way (A with T, C with G)