BIOLOGY

• All life on Earth shares a common chemistry. This provides indirect evidence for evolution.
• Despite their great variety, the cells of all living organisms contain only a few groups of carbon-based compounds that interact in similar ways.
• Key biological molecules


  • Carbohydrates
  • Lipids
  • Proteins
  • Nucleic acids
  • Water
• Monomers


  Smaller units from which larger molecules are made
• Polymers


  Molecules made from a large number of monomers joined together
• Monomers


  • Monosaccharides
  • Amino acids
  • Nucleotides
• Condensation reaction


  Joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water
• Hydrolysis reaction


  Breaks a chemical bond between two molecules and involves the use of a water molecule
• Monosaccharides


  The monomers from which larger carbohydrates are made
• Common monosaccharides


  • Glucose
  • Galactose
  • Fructose

  
• Formation of disaccharides


  Condensation reaction between two monosaccharides to form a glycosidic bond
• Glucose isomers


  α-glucose and β-glucose

  
• Polysaccharides


  Formed by the condensation of many glucose units

  
• Polysaccharides


  • Glycogen (α-glucose)
  • Starch (α-glucose)
  • Cellulose (β-glucose)

  
• Glycogen, starch and cellulose


  • Basic structure and functions
  • Relationship of structure to function in animal and plant cells
• Biochemical tests using Benedict's solution for reducing sugars and non-reducing sugars, and iodine/potassium iodide for starch
• Triglycerides


  Formed by the condensation of one molecule of glycerol and three molecules of fatty acid
• Formation of ester bond in triglycerides


  Condensation reaction between glycerol and a fatty acid (RCOOH)
• Fatty acids

  May be saturated or unsaturated
• Phospholipids


  One of the fatty acids of a triglyceride is substituted by a phosphate-containing group

  
• The different properties of triglycerides and phospholipids related to their different structures
• The emulsion test for lipids
• Calibration curve


  Used to identify the concentration of glucose in an unknown solution

  
• Triglycerides and phospholipids are two groups of lipid
• Triglyceride formation


  Condensation of one molecule of glycerol and three molecules of fatty acid
• Ester bond


  Formed by condensation reaction between glycerol and fatty acid (RCOOH)
• Fatty acids


  • R-group may be saturated or unsaturated
• Different properties of triglycerides and phospholipids


  Related to their different structures
• The emulsion test is used for lipids
• Amino acids


  Monomers from which proteins are made
• General structure of an amino acid


  NH2 (amine group), COOH (carboxyl group), R (side chain)

  
• Peptide bond formation


  Condensation reaction between two amino acids
• Dipeptides


  Formed by condensation of two amino acids
• Polypeptides


  Formed by condensation of many amino acids
• Functional protein may contain one or more polypeptides
• Protein structure


  • Hydrogen bonds, ionic bonds and disulfide bridges play a role
• Proteins have a variety of functions within all living organisms
• The biuret test is used for proteins
• Enzyme


  Lowers the activation energy of the reaction it catalyses
• Properties of an enzyme


  • Related to tertiary structure of active site and ability to combine with complementary substrate(s)