biological molecules

water
1. polar molecule (allow for up take up nutrients as polar molecules)
2. ice forms an insulating layer
3. many hydrogen bonds between molecules
4. high specific heat capacity (not much change due to temperature)
5. less dense when solid (organisms don't freeze/ allow organisms to move)
amino acids
1. contain the amine group (H-N-H), r group (variable, with different charges), carboxylic acid group (HO-C=O)
2. peptide bonds formed by condensation reactions (removal of water), broken by hydrolysis (addition of water)
3. 2 amino acids joined together (dipeptide), many peptides joined together (polypeptide)
4. structures
  1. primary structure (the specific sequence of amino acids in a polypeptide chain)
  2. secondary structure (the polypeptide chain uses hydrogen bonds to form alpha helix or beta folded sheets)
  3. quarternary structure (more than 1 polypeptide chain, which could be haemoglobin or insulin)
  4. tertiary structure (the overall 3-D structure of final protein)
    1. held together by hydrogen bonds, disulphide bonds, ionic bonds (by different charged r groups on amino acids)
    2. globular or fibrous
      1. globular- haemoglobin (soluble in water, made from wide range of amino acids, contain haem group, quarternary alpha hellix)
      2. 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
carbohydrates
1. glucose
  1. beta glucose (has OH on top of carbon 1)
  2. alpha glucose (has OH on bottom of carbon 1)
2. disaccharide
  1. contain 2 units (maltose, 2 alpha glucose units)
3. polysaccharide
  1. contain many repeating units
    1. amylose- straight chain of alpha glucose
    2. amylopectin- branched chain of alpha glucose (in starch)
      1. 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)
    3. glycogen- made from repeating units of alpha glucose
      1. 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)
    4. cellulose- made from repeating units of beta glucose
      1. 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)
lipids
1. oil (liquid at room temp), fats (solid at room temp)
2. saturated (no double bonds), unsaturated (1 or many double bonds)
3. triglyceride- glycersol and 3 fatty acid chains
  1. contain lots of carbon, hydrogen and oxygen,(so good for respiration)
4. phospholipids- glycersol, 2 fatty acid chains, phosphate group
  1. has hydrophobic and hydrophilic parts to form bilayer in membrane
5. cholesterol- 4 fused rings which contain carbon, hydrogen and oxygen
  1. is narrow and hydrophobic so can fit between phospholipids in membrane to give strengh and stability
food tests
1. lipids- emulsion test, boil with ethanol, pour into water (positive, white emulsion forms near top)
2. starch- add iodine (positive, turns brown to blue/black)
3. protein- biuret test, add biuret reagent (positive, blue to lilac)
4. non reducing sugar- boil with HCL acid, cool, do reducing sugar test (positive, blue to brick red)
5. reducing sugars- heat with benedicts solution at 80 degress (positive, blue to brick red)
  1. using colourimeter- concentration of reducing surgar
    1. 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)

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biological molecules

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