biological molecules

biological molecules

1. water

   • polar molecule (allow for up take up nutrients as polar molecules)
   • ice forms an insulating layer
   • many hydrogen bonds between molecules
   • high specific heat capacity (not much change due to temperature)
   • less dense when solid (organisms don't freeze/ allow organisms to move)

2. amino acids

   • contain the amine group (H-N-H), r group (variable, with different charges), carboxylic acid group (HO-C=O)
   • peptide bonds formed by condensation reactions (removal of water), broken by hydrolysis (addition of water)
   • 2 amino acids joined together (dipeptide), many peptides joined together (polypeptide)
   • structures
     • primary structure (the specific sequence of amino acids in a polypeptide chain)
     • secondary structure (the polypeptide chain uses hydrogen bonds to form alpha helix or beta folded sheets)
     • quarternary structure (more than 1 polypeptide chain, which could be haemoglobin or insulin)
     • tertiary structure (the overall 3-D structure of final protein)
       • held together by hydrogen bonds, disulphide bonds, ionic bonds (by different charged r groups on amino acids)
       • globular or fibrous
         • globular- haemoglobin (soluble in water, made from wide range of amino acids, contain haem group, quarternary alpha hellix)
         • fibrous- collagen (non-soluble in water, 35% of the same amino acid, no group, tertiary left handed helix)
           • 3 polypeptide chains in a helix with hydrogen bonds, molecules held together by covalent bonds (fibril), many fibrils to form fibre
             • in walls of arteries, tendons, cartilage

3. carbohydrates

   • glucose
     • beta glucose (has OH on top of carbon 1)
     • alpha glucose (has OH on bottom of carbon 1)
   • disaccharide
     • contain 2 units (maltose, 2 alpha glucose units)
   • polysaccharide
     • contain many repeating units
       • amylose- straight chain of alpha glucose
       • amylopectin- branched chain of alpha glucose (in starch)
         • insoluble (not effect water potential of cells when stored in plant cells), 1,4 glycosidic bonds (easy to hydrolyse), in a spiral (can store more in smaller space)
       • glycogen- made from repeating units of alpha glucose
         • insoluble (not effect water potential of cells when stored in animal cells), 1,4 glycosidic bonds (easily to hydrolyse), 1,6 glycosidic bonds (makes branch and easy for respiration)
       • cellulose- made from repeating units of beta glucose
         • insoluble (form structural part of cell wall), beta glucose (very strong bonding), hydrogen bongs between chains (to give mechanical strength), gaps between macrofibrils (allow some water through)

4. lipids

   • oil (liquid at room temp), fats (solid at room temp)
   • saturated (no double bonds), unsaturated (1 or many double bonds)
   • triglyceride- glycersol and 3 fatty acid chains
     • contain lots of carbon, hydrogen and oxygen,(so good for respiration)
   • phospholipids- glycersol, 2 fatty acid chains, phosphate group
     • has hydrophobic and hydrophilic parts to form bilayer in membrane
   • cholesterol- 4 fused rings which contain carbon, hydrogen and oxygen
     • is narrow and hydrophobic so can fit between phospholipids in membrane to give strengh and stability

5. food tests

   • lipids- emulsion test, boil with ethanol, pour into water (positive, white emulsion forms near top)
   • starch- add iodine (positive, turns brown to blue/black)
   • protein- biuret test, add biuret reagent (positive, blue to lilac)
   • non reducing sugar- boil with HCL acid, cool, do reducing sugar test (positive, blue to brick red)
   • reducing sugars- heat with benedicts solution at 80 degress (positive, blue to brick red)
     • using colourimeter- concentration of reducing surgar
       • do benedicts test, filter out percipitate, pour solution into curvett, set colourimeter using water, test sample, plot transmission reading on calibration curve (already values for known concentrations of reducing sugars)