Biological molecules

• Monomers examples


  • glucose
  • amino acids
  • nucleotides
• Polymers examples

  • starch
  • cellulose
  • glycogen
  • proteins
  • DNA
  • RNA
• Describe a condensation reaction to create polymers

  1. Joining two molecules together

  2. Creating a chemical bond

  3. Removing water
• Describe a hydrolysis reaction to break apart monomers

  1. Breaking of a chemical bond between two molecules

  2. Involves the use of water
• Carbohydrate monosaccharides


  • glucose
  • fructose
  • galactose
• Carbohydrate disaccharides

  • sucrose
  • maltose
  • lactose
• Carbohydrate polysaccharides


  • starch
  • cellulose
  • glycogen
• Alpha glucose


  Hydrogen atom on top, hydroxyl group on bottom of carbon 1
• Beta glucose


  Hydroxyl group on top, hydrogen atom on bottom of carbon 1
• Glycosidic bond


  Chemical bond that forms between two monosaccharides in disaccharides
• Starch


  • Glucose store in plants
  • Made from alpha glucose
• Cellulose


  • Structural strength in plant cell walls
  • Made from beta glucose
• Glycogen


  • Glucose store in animals
  • Made from alpha glucose
  • Highly branched structure
• Triglycerides


  Lipid with 3 fatty acid chains attached to a glycerol molecule
• Phospholipids


  Lipid with 2 fatty acid chains and a phosphate group attached to a glycerol molecule
• Formation of triglycerides


  1. 3 condensation reactions

  2. 3 water molecules lost

  3. 3 ester bonds formed
• Triglycerides

  • High ratio of energy-storing carbon-hydrogen bonds
  • Can act as metabolic water source
  • Do not affect water potential
• Phospholipids


  • Hydrophilic head, hydrophobic tails
  • Form a bilayer in water
• Amino acid


  Central carbon, hydrogen, amine group, carboxyl group, variable R group
• Formation of dipeptide


  1. Condensation reaction

  2. Water removed

  3. Peptide bond formed
• Formation of polypeptide


  1. Multiple condensation reactions

  2. Multiple peptide bonds formed
• Levels of protein structure


  • Primary
  • Secondary
  • Tertiary
  • Quaternary
• Primary structure


  Sequence of amino acids in polypeptide chain
• Secondary structure


  Folding into alpha helix or beta pleated sheet, held by hydrogen bonds
• Tertiary structure


  Further folding into unique 3D shape, held by ionic, hydrogen and disulfide bonds
• Quaternary structure


  Multiple polypeptide chains in a single protein
• Enzymes


  • Proteins in tertiary structure
  • Catalyze reactions by lowering activation energy
  • Have specific active sites complementary to substrates
• Induced fit model


  Enzyme active site slightly changes shape to mold around substrate
• Factors affecting enzyme-controlled reaction rate


  • Temperature
  • pH
  • Substrate concentration
  • Enzyme concentration
  • Inhibitors
• Lower temperature


  Less kinetic energy, fewer successful collisions, fewer enzyme-substrate complexes, lower reaction rate
• pH away from optimum


  Enzyme denaturing, loss of active site shape, fewer enzyme-substrate complexes, lower reaction rate
• Increasing substrate concentration


  More collisions, more enzyme-substrate complexes, higher reaction rate until active sites saturated
• Increasing enzyme concentration


  More active sites available, higher reaction rate until substrate becomes limiting
• Competitive inhibitor


  Binds to active site, preventing substrate binding
• Non-competitive inhibitor


  Binds elsewhere on enzyme, changing active site shape
• Competitive inhibitor


  Binds to the active site of an enzyme, preventing the substrate from binding
• Non-competitive inhibitor


  Binds to the allosteric site of an enzyme, changing the shape of the active site and preventing the substrate from binding
• Biochemical test for starch


  1. Add iodine

  2. Positive test result: iodine goes from orangey brown to blue black
• Biochemical test for reducing sugars

  1. Add Benedict's reagent and heat

  2. Positive test result: solution turns green, yellow, orange or brick red (depending on concentration)
• Biochemical test for non-reducing sugars


  1. Perform Benedict's test for reducing sugars (negative result)

  2. Add acid and boil

  3. Cool and neutralise

  4. Add Benedict's reagent and heat

  5. Positive test result: solution turns orange or brick red