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 carbonbased compounds that interact in similar ways.
• Carbonbased compounds in cells


  • 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 of two monosaccharides
• Disaccharides


  • Maltose
  • Sucrose
  • Lactose
• Glucose isomers


  α-glucose and β-glucose
• Polysaccharides


  Formed by the condensation of many glucose units
• Polysaccharides


  • Glycogen
  • Starch
  • Cellulose
• Glycogen, starch and cellulose


  • Basic structure and functions
• Structure of glycogen, starch and cellulose


  Relationship to function in animal and plant cells
• Biochemical tests


  1. Benedict's solution for reducing sugars and non-reducing sugars

  2. Iodine/potassium iodide for starch
• Triglycerides


  Formed by the condensation of one molecule of glycerol and three molecules of fatty acid
• Phospholipids

  One of the fatty acids of a triglyceride is substituted by a phosphate-containing group
• Properties of triglycerides and phospholipids

  Related to their different structures
• Emulsion test


  For lipids
• Amino acids


  The monomers from which proteins are made
• Peptide bond


  Formed by a condensation reaction between two amino acids
• Dipeptides


  Formed by the condensation of two amino acids
• Polypeptides


  Formed by the condensation of many amino acids
• Protein structure


  • Role of hydrogen bonds, ionic bonds and disulfide bridges
• Protein functions


  Variety of functions within all living organisms
• Protein structure


  Relationship to protein function
• Biuret test


  For proteins
• Enzyme


  Lowers the activation energy of the reaction it catalyses
• Properties of enzymes


  • Relate to the tertiary structure of the active site and ability to combine with complementary substrate(s)
• Factors affecting rate of enzyme-controlled reactions

  • Enzyme concentration
  • Substrate concentration
  • Concentration of competitive and non-competitive inhibitors
  • pH
  • Temperature
• DNA and RNA are important information-carrying molecules
• DNA nucleotide


  Components: deoxyribose, phosphate group, one of the organic bases (adenine, cytosine, guanine or thymine)
• RNA nucleotide


  Components: ribose, phosphate group, one of the organic bases (adenine, cytosine, guanine or uracil)
• Formation of phosphodiester bond


  Between two nucleotides in a condensation reaction
• DNA molecule


  Double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs
• RNA molecule


  Relatively short polynucleotide chain
• Semi-conservative replication of DNA

  1. Unwinding of double helix

  2. Breakage of hydrogen bonds between complementary bases

  3. Role of DNA helicase

  4. Attraction of new DNA nucleotides to exposed bases on template strands and base pairing

  5. Role of DNA polymerase in condensation reaction