biological molecules

• polymer = long chain of molecules, made of repeated monomers
• carbohydrates = polymer, sugars are the monomer
• proteins = polymer, amino acids are the monomers
• cations - electrons that have been lost, giving a positive charge

  • calcium - nerve impulse transmission
  • sodium - nerve impulse transmission
  • potassium - nerve impulse transmission
  • hydrogen - pH determination
  • ammonium - production of nitrates
• anions - electrons have been gained giving a negative charge

  • nitrate - component of amino acids
  • hydrogen carbonate - carbon dioxide transport
  • chloride - balance of sodium and potassium ions
  • phosphate - nucleic acid and atp formation
  • hydroxide - pH determination
• when inorganic ions dissolve in water they are called electrolytes
• water

  • hydrogen bonds are weak
  • slightly negative oxygen end
  • slightly positive hydrogen end
• properties of water

  • liquid - providing habitat
  • density - ice is insulating
  • cohesion - cohesion tension theory
  • adhesion - capillary action
  • good solvent - polar molecules dissolve
  • high specific heat capacity - energy required to break hydrogen
  • high latent heat of vaporisation - become a gas
• carbohydrate

  • general formula = (CH2O)n
  • source of energy - glucose
  • store of energy - glycogen and starch
  • structural units - cellulose and chitin
  • components of nucleic acids and glycolipids
• monosaccharides

  • sweet, soluble in water, form crystals
  • can be straight chain or ring form
  • e.g., triose, pentose, ribose, deoxyribose, hexose
• a glucose + a glucose = maltose
• a glucose + fructose = sucrose
• a glucose + galactose = lactose
• disaccharides - two monosaccharides joined together

  • properties = sweet, soluble in water, form crystals
• condensation reaction - water is made and two monomers are joined
• hydrolysis - the breaking of a bond using water
• polysaccharides - repeating monomers of monosaccharides, contains glycosidic bonds
• glycosidic bond - between two sugars
• properties of polysaccharides

  • insoluble in water
  • not sweet
  • can't be crystallised
• starch

  • found in plants
  • a glucose molecules
  • made from amylose and amylopectin
• amylose

  • a glucose
  • 1,4 glycosidic bonds
  • spiral shape
• amylopectin

  • a glucose
  • 1,4 and 1,6 glycosidic bonds
  • spiral shape
• functions of starch

  • insoluble - does not affect water potential
  • branched - glucose can be quickly released by enzymes
  • compact - good storage molecule
• glycogen

  • a glucose
  • 1,4 and 1,6 glycosidic bonds
  • branched
  • more compact than amylopectin
• functions of glycogen

  • insoluble in water - does not affect water potential
  • branched - glucose can be released quickly for respiration
  • compact - good energy store
• cellulose -

  • unbranched, straight chain
  • b glucose molecules rotate 180
  • 1,4 glycosidic bonds
  • held together by hydrogen bonds forming fibres (microfibrils)
  • microfibrils join to form macrofibrils
  • macrofibrils join to form fibres
  • fibres criss cross to provide extra strength
• functions of cellulose

  • cell walls - microfibrils have a very high tensile strength due to glycosidic bonds, preventing bursting when turgid. Spaces between the fibres allow the membrane to be fully permeable
  • fibre - cellulose forms the fibre in our diets and is needed to help maintain a healthy digestive system
• starch test

  1. add a couple of drops of iodine to the test sample

  • starch present = blue/black
  • no starch = remain brown
• reducing sugars test - all monosaccharides, maltose and lactose

  1. add Benedict's solution
  2. heat in a water bath for 3 mins
  3. glucose = brick red precipitate, may also be present if solution is blue,green

  • allows for a qualitative comparison
• non reducing sugar - sucrose

  1. add hydrochloric acid and boil in water bath
  2. cool tube and add an alkali (sodium hydrogen), test with universal indicator
  3. repeat Benedict's again
• reagent strips - a strip is dipped into the solution and then compared to the colour it changes to within the calibration chart provided, allow for a quantitative measure
• colorimetry - shine a light through a sample and measures how much light is transmitted, the more concentrated the less greater the absorbance by the solution and therefore less transmission
• biosensors - uses a biological molecule to detect a chemical and convert it to an electrical signal, acts as a transducer
• serial dilution allows you to make a wider range of concentrations more accurately than a standard dilution
• lipids

  • macromolecules
  • carbon, hydrogen, oxygen
  • soluble in organic solvents
  • can be: triglycerides, phospholipids, cholesterol
• function of lipids

  • structural - phospholipid bilayer
  • thermal insulation - reduce heat loss
  • electrical insulation - myelin sheath
  • protection of organs
  • waterproofing
  • buoyancy
• structure of triglycerides

  • one glycerol
  • 3 fatty acids
  • ester bond
• glycerol structure - alcohol with 3 carbons and 3 OH groups
• fatty acid structure

  • carboxyl group: COOH
  • hydrocarbon tail
  • either saturated - no carbon double bonds, unsaturated - carbon double bonds leading to kinks, kinks reduces the melting point
  • monounsaturated - one carbon double bond
  • polyunsaturated - 2+ carbon double bonds
• esterification - the formation of a triglyceride