Whole

• Bonding


  • Covalent bonding - sharing of electrons between two non-metals
  • Ionic bonding - transfer of electrons from a metal to a non-metal, forming positive and negative ions
  • Hydrogen bonding - weak attraction between opposite dipoles
• Monomer


  Smaller unit from which larger molecules are made
• Polymer


  Molecule made from a large number of monomers joined together in a chain
• Examples of monomers and polymers

  • Amino acid (monomer) - Protein (polymer)
  • Nucleotide (monomer) - DNA/nucleic acid (polymer)
  • Glucose (monomer) - Polysaccharide/carbohydrate (polymer)
• Hydrolysis


  Breaking a chemical bond using water
• Condensation


  Joining two molecules together, creating a chemical bond and eliminating another molecule (usually water)
• Monosaccharide


  Single sugar, monomer for carbohydrates
• Alpha glucose and beta glucose


  • Differ in the spatial arrangement of the hydrogen and OH group
  • Cannot be superimposed, like left and right hand
• Monosaccharides


  • Glucose
  • Galactose
  • Fructose
• Disaccharide


  Two monosaccharides joined together
• Polysaccharide


  Many monosaccharides joined together
• Starch


  • Polymer of alpha glucose, found in plant cells
  • Insoluble, can be coiled and branched, used for energy storage
• Glycogen


  • Polymer of alpha glucose, found in animal cells
  • Highly branched, can be broken down quickly for energy
• Cellulose


  • Polymer of beta glucose, found in plant cell walls
  • Long straight unbranched chains, cross-linked by hydrogen bonds, provides structural support
• Benedict's test


  Test for reducing sugars - add Benedict's solution and heat, positive result is brick red precipitate
• Iodine test


  Test for starch - add iodine, positive result is blue-black colour
• Lipid


  Insoluble in water but soluble in organic solvents, great store of energy
• Triglycerides


  • Made up of 3 fatty acids joined to glycerol by ester bonds
  • Can be saturated, unsaturated, or polyunsaturated
• Phospholipids


  • Made up of 2 fatty acids and a phosphate group joined to glycerol
  • Hydrophilic head and hydrophobic tails, form cell membrane bilayer
• Amino acid


  Contains a central carbon, amino group, carboxyl group, and variable side group (R group)
• Peptide bond formation


  Two amino acids join in a condensation reaction, losing water
• Dipeptide


  Two amino acids joined together
• Polypeptide


  Many amino acids joined together
• Protein structure


  • Primary - sequence of amino acids
  • Secondary - alpha helix or beta pleated sheet
  • Tertiary - further folding and bonding
  • Quaternary - multiple polypeptide chains
• Protein test


  Mix sample with NaOH and copper sulfate, positive result is purple colour
• Alpha helix


  Secondary structure of proteins formed by hydrogen bonds between the carbonyl oxygen and amino hydrogen of the polypeptide backbone
• Beta-pleated sheet


  Secondary structure of proteins formed by hydrogen bonds between polypeptide chains arranged in parallel or antiparallel layers
• Protein folding


  1. Alpha helices and beta-pleated sheets form

  2. Further folding occurs to give rise to tertiary structure

  3. Hydrogen bonding, disulfide bridges, ionic bonding between R-groups determine tertiary structure
• Quaternary structure


  The highest level of protein structure, involving the aggregation of more than one polypeptide chain
• Types of proteins


  • Fibrous proteins
  • Globular proteins (e.g. enzymes, hemoglobin)
• Enzymes


  Biological catalysts that lower the activation energy required for a reaction to take place
• Uncatalyzed reaction


  Reaction progress goes up and down, with a peak in energy required to start the reaction
• Enzyme-catalyzed reaction


  Enzyme lowers the activation energy needed for the reaction to start
• Enzyme specificity


  Enzymes have a specific and complementary active site shape that only binds to a narrow range of substrates
• Induced fit model


  The active site of an enzyme changes shape slightly to better accommodate the substrate, unlike the rigid lock-and-key model
• Measuring enzyme reaction rate

  1. Measure product formation or substrate depletion

  2. Plot changes over time (volume of gas, mass, color, pH)

  3. Qualitative (yes/no) or quantitative (using equipment) tests
• As temperature increases


  Enzyme reaction rate increases due to more collisions, but then decreases as enzyme denatures
• Enzyme optimum temperature


  The temperature at which an enzyme's reaction rate is maximized, before denaturation occurs
• pH


  The concentration of hydrogen ions in a solution, ranging from acidic (low pH) to alkaline (high pH)
• Extreme pH


  Disrupts ionic bonds in enzyme tertiary structure, causing denaturation