Biological molecules

• polymerisation 


  joining of monomers to form polymer chains
• what are the 4 carbon-based compounds?

  protein, lipids, carbohydrates and nucleic acid
• monomers:

  • monosacchraide
  • amino acid
  • nucleotides


  polymers:

  • polysaccharide
  • protein- polypeptide
  • DNA- polynucleotides
• two main functions of carbohydrates in living organisms?

  Energy storage- starch (plants) glycogen (animals)

  structural support- cell wall (cellulose)
• Monosaccharides

  • simple sugars
  • all reduce in Benedict's solution
  • all sweet tasting
  • soluble
  • easily transported
• What does reducing mean?

  Sugar looses electrons to the Benedict's solution
• which disaccharides are reducing sugars?

  • maltose
  • lactose
• name the monosaccharides which are reducing sugars?

  Glucose and fructose and galatose
• What is Benedict's reagent made of?

  Copper 2 sulfate
• why is the Benedict's test semi-quantitive?

  Because the Benedict's test measures the presence and approximate amount of reducing sugars in a solution, but it does not provide an exact quantitative measurement.
• • glucose + glucose = maltose
  • glucose + fructose= sucrose
  • glucose + galactose = lactose
• How to test for a reducing sugar?

  • Place set volume of liquid solution in test tube
  • add same volume of Benedict's reagent
  • place in water bath at 90 degrees for 3-5 minutes
  • red= positive test
• How to test for non-reducing sugars?

  • carry out Benedict's test
  • if negative result
  • boil solution with hydrochloric acid
  • add sodium hydrogen carbonate powder
  • add Benedicts reagent and heat in water bath
  • view results
• Polysaccharide- Starch

  Monomer- alpha glucose

  Glycosidic bond- 1-4/1-6

  Structure- branched, compact and helical
• Polysaccharide- cellulose

  Monomer- beta glucose

  Glycosidic bond- 1-4

  Structure- unbranched, straight
• Polysaccharide- glycogen

  Monomer- alpha glucose

  glycosidic bonds- 1-4/1-6

  structure- highly branched
• Amylopectin- long, branched structure ideal for quick energy release
• Amylose- long, unbranched helical structure ideal for storage
• Glycogen is similar in structure to starch but has shorter chains and is more highly branched
• Importance of cellulose in plant cell walls?

  Structural support, turgor pressure
• What is the structure of cellulose?

  Cellulose is a linear polymer composed of glucose units linked together by beta-1,4-glycosidic bonds. It has straight parallel chains with hydrogen bonds in-between layers
• What are the differences between triglyceride and phospholipids?

  Triglyceride- contains 3 fatty acids and doesn't have a phosphate group

  Phospholipids- contains 2 fatty acids and contains a phosphate group
• What are the similarities between triglycerides and phospholipids?

  • both contain glycerol molecule
  • both contain fatty acids
  • both contain carbon, hydrogen and oxygen
  • molecules are joined by ester bonds formed through condensation reactions
• How to carry out the emulsion test

  • Add a small sample of liquid food sample into test tube
  • as a control use water in another test tube
  • add 5cm cubed of ethanol
  • shake vigorously to dissolve the liquid sample
  • add 5cm cubed of distilled water and shake gently
  • contents of the tube turns cloudy white
• Describe the structure of a protein

  • polymer of amino acids
  • joined by peptide bonds
  • formed by condensation reaction
  • order of amino acids is the primary structure
  • folded into alpha helix or beta pleated sheets as secondary structure
  • 3-D shape as tertiary structure
• Describe how proteins are broken down in the human gut

  • hydrolysis of peptide bonds
  • endopeptidases break polypeptides into smaller peptide chains
  • exopeptidase remove terminal amino acid
  • dipeptidases breaks down dipeptides into amino acids
• Role of lipids

  • Energy source
  • waterproofing- waxy cuticle
  • insulation
  • protection- layer of fat around important organs