Biological molecules

• Food


  Contains nutrients including carbohydrates, fats, proteins and water
• Water


  Very crucial to our body as about 70% of our body weight is water
• Types of carbohydrates


  • Simple sugars
  • Double sugars
  • Complex carbohydrates
• Sugars

  Sweet, when they dissolve in water they lower the water potential of the solution
• Types of sugars


  • Simple sugars
  • Double sugars
• Simple sugars


  Include glucose and fructose (fruit sugar), basic unit of carbohydrates, can pass through cell membrane
• Double sugars


  Result of combination of two simple sugars, can be split into single sugars by enzymes
• Double sugars


  • Maltose
  • Sucrose
• Complex carbohydrates


  Formed by many similar molecules of single sugars joining together, examples are starch, cellulose and glycogen
• Types of complex carbohydrates


  • Starch
  • Cellulose
  • Glycogen
• Starch


  • Large molecule formed from many units of glucose, can be digested to glucose to provide energy, not formed or stored by animals, relatively insoluble and ideal for storage, found in plant storage organs
• Cellulose


  • Consists of numerous units of glucose molecules linked differently than starch, not easily broken down in human digestive system, major component of dietary fibre, protects plant cells
• Glycogen


  • Formed by many glucose molecules into a highly branched molecule, storage form of carbohydrates in mammals, can be digested to glucose to provide energy, stored in liver and muscles
• Functions of carbohydrates


  • Source of energy
  • Forming supporting structures
  • Conversion to other organic compounds
  • Formation of nucleic acids
  • Production of nectar
  • Synthesis of lubricants
• Reducing sugars


  Sugars that have reducing properties and produce a red precipitate when boiled with Benedict's solution, includes glucose, fructose, maltose
• Starch test


  Add iodine solution, changes to blue-black when starch is present
• Fats


  A type of lipid, can be animal fats or plant fats, enzymes help break them down into glycerol and fatty acids
• Sources of fats


  • Butter, cheese, fatty meat, nuts, peas, beans, palm oil, fish like salmon and herring
• Functions of fats


  • Energy source
  • Insulation
  • Solvent
  • Prevention of water loss
  • Constituent of protoplasm
• Fat test


  Ethanol emulsion test, forms a white emulsion when ethanol and water are added to fats and shaken
• Proteins


  Always present in all cells, amino acids are the building blocks
• Amino acids


  • Have an amino group, an acidic group, and a side chain, there are 20 different naturally occurring ones
• Polypeptide


  Different amino acids join together in a linear sequence to form a polypeptide
• Protein molecule


  One or more longer chains of amino acids interact and combine to form a protein molecule that is folded into a 3D shape
• Sources of proteins


  • Animal sources like milk, eggs, seafood, meat, plant sources like soya beans, nuts, grains, vegetables
• Functions of proteins


  • Synthesis of new cytoplasm, for growth and repair
  • Synthesis of enzymes and some hormones
  • Formation of antibodies to fight diseases