BIOCHEM LAB

• Carbohydrates


  Organic compounds composed of carbon, hydrogen and oxygen that act as the primary source to provide energy for living organisms
• Saccharides


  Another term for carbohydrates
• Sugars


  Carbohydrates with a sweet taste
• Classification of carbohydrates based on reactivity

  • Reducing sugars
  • Non-reducing sugars
• Reducing sugars


  Carbohydrates that can reduce Tollen's, Benedict's or Fehling's reagents (have a free aldehyde or ketone group)
• Reducing sugars


  • Maltose
  • Lactose
• Non-reducing sugars


  Carbohydrates that cannot reduce Tollen's, Benedict's or Fehling's reagents
• Non-reducing sugars


  • Sucrose
• Molisch's test


  1. Add Molisch's reagent (10% alcoholic solution of α-naphthol) and concentrated sulfuric acid

  2. Carbohydrates undergo dehydration to form furfural that reacts with α-naphthol to form a violet colored product

  
• The appearance of a purple or violet ring confirms the presence of carbohydrates in Molisch's test
• Fehling's test


  1. Add Fehling's solution A (copper sulfate) and Fehling's solution B (potassium sodium tartrate) to aqueous carbohydrate solution and heat

  2. Reducing sugars reduce the deep blue copper(II) ions to a red precipitate of copper(I) oxide

  
• The appearance of a red precipitate confirms the presence of reducing sugars in Fehling's test
• Benedict's test


  1. Add Benedict's reagent (contains copper(II) ions) to aqueous carbohydrate solution and heat

  2. Reducing sugars reduce the copper(II) ions to form a red precipitate of copper(I) oxide

  
• The appearance of a red precipitate confirms the presence of reducing sugars in Benedict's test
• Tollen's test


  1. Add Tollen's reagent (ammoniacal silver nitrate solution) to aqueous carbohydrate solution

  2. Reducing sugars reduce the silver ions to form a silver mirror on the inner walls of the test tube
• The appearance of a silver mirror confirms the presence of reducing sugars in Tollen's test
• Iodine test


  1. Add iodine solution (in potassium iodide) to a sample

  2. Iodine reacts with starch to form a blue-black starch-iodine complex

  
• The appearance of a blue-black color confirms the presence of starch in the iodine test

  
• Water is vital to living organisms
• Water makes up roughly 50-95% of the composition of living cells, depending on their function and nutrient content
• Water


  A chemical compound with unique physical and chemical properties that make it an ideal compound for life
• Water forms hydrogen bonds


  • These weak bonds that collectively are very strong make possible most of water's unique properties, such as cohesive and adhesive properties, high specific heat, high heat of vaporization and polarity
• Hydrogen bonds


  Weak bonds that form between hydrogen atoms of one molecule and the lone pair(s) of neighboring electronegative atoms
• Hydrogen bonding


  • Allows for water molecules to be both adhesive (sticking to other surfaces) and cohesive (sticking to each other)
  • Critical to living organisms, as water is able to reach the tops of the tallest trees due to adhesion and cohesion
  • Causes capillary action in plants and non-living objects
• Water is polar


  Water has both a positive and a negative charge on its molecular structure due to the unpaired electrons of the oxygen atom
• Water is not a universal solvent, as it is unable to dissolve nonpolar molecules such as lipids and some proteins</b>
• Water has a high surface tension


  • Due to hydrogen bonding, creating a 'net' of water molecules that allows some organisms to walk on water
  • Causes water to bead up on waxy surfaces
  • Must be reduced for cleaning purposes using surfactants
• Heat of vaporization


  The energy required to change water from a liquid into a gas (2260 J/g)
• Water is less dense as a solid than as a liquid
• Ice floating on top of bodies of water provides insulation for the life below and prevents organisms' bodies from freezing solid in the winter
• Capillary Action


  1. Cut paper towel strip

  2. Tape to pencil

  3. Place in water

  4. Observe
• Cohesion


  1. Place coins in water, soapy water, and alcohol

  2. Observe number of drops that can fit on each coin
• Water Polarity


  1. Add salt and sugar to water and alcohol

  2. Observe what happens

  3. Form puddle on wax paper and glass slide, observe
• Surface Tension


  1. Float paper clip on water

  2. Add soap, observe
• Vaporization


  Measure time for water, 40% ethanol, and 70% ethanol to evaporate