topic 1

• Monomers


  Smaller / repeating molecules from which larger molecules / polymers are made
• Polymers


  Molecules made up of many identical / similar molecules / monomers
• Condensation reaction


  1. 2 molecules join together

  2. Forming a chemical bond

  3. Releasing a water molecule

  
• Hydrolysis reaction


  1. 2 molecules separated

  2. Breaking a chemical bond

  3. Using a water molecule

  
• Polymers


  • Nylon
  • Polyethylene
  • Polyester
  • Teflon
  • Epoxy
• Monosaccharides


  • Glucose
  • Fructose
  • Galactose
• α-glucose


  OH group is below carbon 1
• β-glucose


  OH group is above carbon 1
• Disaccharides


  Two monosaccharides joined together with a glycosidic bond
• Common disaccharides


  • Maltose (glucose + glucose)
  • Sucrose (glucose + fructose)
  • Lactose (glucose + galactose)
• Polysaccharides


  Many monosaccharides joined together with glycosidic bonds
• Starch


  • Energy store in plant cells
  • Polysaccharide of α-glucose
  • Amylose - 1,4-glycosidic bonds → unbranched
  • Amylopectin - 1,4- and 1,6-glycosidic bonds → branched
• Glycogen


  • Energy store in animal cells
  • Polysaccharide made of α-glucose
  • 1,4- and 1,6-glycosidic bonds → branched
• Structure of starch and glycogen

  Relates to their functions
• Cellulose


  • Provides strength and structural support to plant / algal cell walls
  • Polysaccharide of β-glucose
  • 1,4-glycosidic bond → straight, unbranched chains
  • Chains linked in parallel by hydrogen bonds forming microfibrils

  
• Structure of cellulose relate to its function 


  beta glucose is inverted in a long unbranded chain-many hydrogen bonds link parallel strands to form microfibrils Hydrogen bonds are strong and high in number-provides strength to plant
• Reducing sugars


  Monosaccharides, maltose, lactose
• Test for reducing sugars

  1. Add Benedict's solution

  2. Heat in boiling water bath

  3. Positive result = green / yellow / orange / red precipitate
• Test for non-reducing sugars

  1. Do Benedict's test and stays blue / negative

  2. Heat in boiling water bath with acid (to hydrolyse into reducing sugars)

  3. Neutralise with alkali

  4. Heat in boiling water bath with Benedict's solution

  5. Positive result = green / yellow / orange / red precipitate
• Measure quantity of sugar in solution

  Carry out Benedict's test, filter and dry precipitate, find mass/weight
• Measure quantity of sugar in solution

  1. Make sugar solutions of known concentrations

  2. Heat with Benedict's solution, measure absorbance with colorimeter

  3. Plot calibration curve, measure unknown sample absorbance and read off curve
• Test for starch


  Add iodine dissolved in potassium iodide, positive result = blue-black
• Lipids


  Triglycerides and phospholipids
• Fatty acid


  • Variable R-group - hydrocarbon chain (saturated or unsaturated)
  • -COOH = carboxyl group
• Saturated fatty acid


  No C=C double bonds in hydrocarbon chain, all carbons fully saturated with hydrogen
• Unsaturated fatty acid


  One or more C=C double bond in hydrocarbon chain (creating bend / kink)
• Triglyceride formation


  1. 1 glycerol molecule and 3 fatty acids

  2. Condensation reaction

  3. Removing 3 water molecules

  4. Forming 3 ester bonds

  
• Phospholipids


  One of the fatty acids of a triglyceride is substituted by a phosphate-containing group
• Properties of phospholipids


  Relate to their structure
• Test for lipids


  Add ethanol, shake, then add water, positive = milky white emulsion
• Amino acid


  • COOH = carboxyl group
  • R = variable side chain / group
  • H2N = amine group
• The 20 amino acids that are common in all organisms differ only in their side group (R)
• Amino acid joining


  1. Condensation reaction

  2. Removing a water molecule

  3. Between carboxyl / COOH group of one and amine / NH2 group of another

  4. Forming a peptide bond
• Dipeptide


  2 amino acids joined together
• Polypeptide


  Many amino acids joined together
• Primary structure of protein

  Sequence of amino acids in a polypeptide chain, joined by peptide bonds
• Secondary structure of protein

  • Folding (repeating patterns) of polypeptide chain eg. alpha helix / beta pleated sheets
  • Due to hydrogen bonding between amino acids
• Tertiary structure of protein


  • 3D folding of polypeptide chain
  • Due to interactions between amino acid R groups (dependent on sequence of amino acids)
  • Forming hydrogen bonds, ionic bonds and disulfide bridges
• Quaternary structure of protein

  • More than one polypeptide chain
  • Formed by interactions between polypeptides (hydrogen bonds, ionic bonds, disulfide bridges)
• Test for proteins


  Add biuret reagent, positive result = purple / lilac colour (negative stays blue) → indicates presence of peptide bonds