bio chap3: biological molecules

• Carbohydrates


  Made of elements carbon, hydrogen, oxygen
• single sugars

  • Glucose (plants)
  • Fructose
  • Sucrose
• reducing sugar


  • Can pass through cell membrane
  • Tested for using Benedict's test
• Reducing sugars


  Glucose, fructose, maltose
• Benedict's test for reducing sugars

  1. Add sample to Benedict's solution

  2. Heat in boiling water bath for 2-3 minutes

  3. Green, yellow, red precipitate forms if sugar is present
• Non-reducing sugars


  Remain blue in Benedict's test
• Complex carbohydrates


  Made up of many similar molecules of single sugar joined together to form large molecule
• Complex carbohydrates


  • Starch
  • Glycogen
  • Cellulose
• Starch


  • Storage form of carbohydrates in plants
  • Can be digested to glucose to provide energy
• Cellulose


  • Cell wall component in plants
  • Cannot be digested in human intestines
  • Acts as dietary fibre
• Glycogen


  • Storage form of glucose in mammals
  • Digested to provide energy for cellular activities
  • Stored in liver and muscle
• Types of Molecules


  • Carbohydrates
  • Lipids
  • Proteins
• Carbohydrates


  Molecules made up of carbon, hydrogen and oxygen
• Complex carbohydrates


  • Starch
  • Glycogen
• Starch


  Carbohydrate storage molecule in plants
• Glycogen


  Carbohydrate storage molecule in animals
• Starch and glycogen


  Both are stores of glucose
• Starch and glycogen


  • They are insoluble in water
  • They are compact in shape and occupy less space than the individual glucose units that make them up
• Digestion of starch


  1. Bonds within the polysaccharide are broken

  2. Glucose molecules are released
• Amylase


  Enzyme that digests starch
• Amylase cannot break down maltose to glucose</b>
• Complete digestion of starch

  1. Amylase breaks down starch to maltose

  2. Maltase further breaks down maltose to glucose
• Lipids


  Molecules made of carbon, hydrogen and oxygen, with a high proportion of hydrogen
• Lipids


  • Can be broken down for energy
  • Act as an insulating material to prevent heat loss
  • Solvent for fat-soluble vitamins and other fat-soluble substances
• Proteins


  Molecules made up of carbon, hydrogen, oxygen, nitrogen and sometimes sulfur
• Amino acids


  Simpler compounds that proteins are built up from
• Proteins


  • Made up of one or more polypeptide chains
  • Involved in the synthesis of new cytoplasm, enzymes, hormones and antibodies
• Test for starch


  1. Add iodine solution

  2. Blue-black colour indicates presence of starch

  3. Brown colour indicates absence of starch
• Test for fats


  1. Add ethanol

  2. White emulsion indicates presence of fats
• Test for proteins


  1. Add biuret solution

  2. Violet colour indicates presence of proteins

  3. Blue colour indicates absence of proteins