F212 - Biological Molecules

F212 - Biological Molecules

1. Water

   • Water is a polar molecule.
     • It can form hydrogen bonds
   • Properties of Water
     • Solvent
       • Metabolic processes rely on chemicals being able to react together
     • Liquid
       • Movement of materials requires a liquid transport medium
     • Cohesion
       • creates surface tension and makes long, thin water columns very stong
   • More Properties of Water
     • Freezing
       • Water below a frozen surface becomes insulated and less likely to freeze
     • Thermal Stability
       • Large bodies of water have fairly stable temperatures. Evaporation of water can col surfaces by removing heat
     • Metabolic
       • Water takes part as a reactant in some processes.

2. Proteins

   • Amino Acids
     • Structure
     • Peptide Bonds
       • Synthesis
         • The –OH from one amino acid and the –H from another are removed to make water, and the C and the N join together via a peptide bond
       • Hydrolysis
         • A water molecule is used to break the peptide bond. The –H joins back to the N, and the –OH back to the C
   • Structure of Proteins
     • Primary
       • The unique sequence of amino acids
     • Secondary
       • Coiling of pleating parts of the polypeptide
         • β-pleated sheet
         • α-helix
     • Tertiary
       • overall '3D' structure
         • Hydrogen Bonding, Ionic Bonding, Hydrophobic Bonds, Disulfide Bridges
     • Quarternary
       • more than one polypeptide chain
         • e.g. Haemoglobin - four polypeptide chains
   • Collagen
     • Three polypeptide chains with hydrodgen bonds and cross links - the cross links are staggered to make the molecule stronger.
   • Haemoglobin vs. Collagen

3. Carbohydrates

   • Glucose
     • Alpha / Beta
       • OH below plane / OH above plane
   • Glycosidic Bonds
     • Synthesis
       • The –OH from one glucose and the –H from another are removed to make water, and the O and the C join together via a glycosidic bond
     • Hydrolysis
       • A water molecule is used to break the glycosidic bond. The –H joins back to the O, and the –OH back to the C4
   • Amylose vs. Cellulose
   • Structure of Glycogen
     • Mostly 1,,4/ 9% are 1,6
   • Relating Structure to Function
     • Glucose
       • Simplest sugar - used in respiration
     • Amylose
       • insoluble in water - doesn't affect ψ
     • Glycogen
       • Many branches means it can be hydrolysed easily
     • Cellulose
       • very strong and arrangement of macrofibrils allows water to move in and out easily and determines how a cell can grow or change shape
     • Triglyceride
       • compact energy store, insoluble in water - doesn't affect ψ
     • Cholseterol
       • Small, thin molecules - fit into the lipid bilayer giving strength and stability
     • Phospholipid
       • Part hydrophilic/part hydrophobic - idea for cell membranes
   • Triglyceride
     • Glycerol,three fatty acids
   • Phospholipid
     • Glycerol , two fatty acids ,phosphate

4. Colorimetry

   • Chemical Tests
     • protein (biuret) test
       • pale blue to lilac
     • reducing sugars - Benedict's test
       • add Benedict’s, heat to 80˚C - blue to orange-red
     • non-reducing sugars - Benedict's test
       • If RS is - boil with HCl, cool and neutralise with NaHCO3. repeat Benedict’s test.
     • starch (iodine) test
       • yellow to blue-black
     • lipids (emulsion) test
       • Mix the ethanol, pour into water - emulsion forms if a lipid is present
   • Determining concentration of glucose in a solution
     • Perform Benedict's test on the solution until there is no further colour change.
       • Cool and filter solution
         • Take filtrate and test using a colorimeter
           • Low reading for absorbance means higher conc. of reducing sugar.
           • High reading for absorbance means lower conc. of reducing sugar

Images and files in the map