chapter3

• Organic Chemistry

  Study of carbon compounds
• Organic chemistry deals with a great variety of different compounds
• Versatility of carbon


  • Atomic number = 6
  • Six protons and six electrons
  • 4 valence electrons
  • Forms 4 non-polar bonds (usually covalent)
  • Arrangement of bonds is a tetrahedral shape
• Covalent bonds


  • Single—sharing 1 pair of electrons
  • Double—sharing 2 pairs of electrons
  • Triple—sharing 3 pairs of electrons
• The length, angle, and direction of bonds between any two elements are always the same
• Methane


  • Always forms a tetrahedron
• Molecules in living organisms

  • Proteins
  • Carbohydrates
  • Lipids
  • Nucleic acids
• Living organisms are carbon-based. The 4 classes of biological molecules all contain large numbers of carbon atoms
• Polymers


  Most biological molecules are polymers of smaller molecules called monomers
• Biological polymers

  • Proteins: combinations of 20 amino acids
  • Carbohydrates: sugar monomers (monosaccharides) are linked to form polysaccharides
  • Nucleic acids: 4 kinds of nucleotide monomers
  • Lipids: noncovalent forces maintain interactions between lipid monomers
• Biochemical unity: the four kinds of macromolecules are present in roughly the same proportions in all living organisms, and have similar functions
• Hydrocarbons


  The backbone of biological molecules - organic molecules consisting of carbon and hydrogen atoms
• Functional groups


  Groups of atoms with specific chemical properties and consistent behavior
• A single macromolecule may contain many different functional groups
• Isomers


  Molecules with the same chemical formula, but atoms are arranged differently
• Structural isomers


  Differ in how their atoms are joined together
• Optical isomers


  Occur when a carbon atom has four different atoms or groups of atoms attached to it
• Molecules that only differ in spatial arrangement are referred to as Enantiomers
• Some biochemical molecules that can interact with one optical isomer are unable to "fit" the other
• Polymer formation


  1. Monomers are joined by covalent bonds in condensation reactions

  2. A water is removed; so they are also called dehydration reactions
• Organic Chemistry


  Study of carbon compounds
• Polymer breakdown


  Polymers are broken down into monomers in hydrolysis reactions
• Organic chemistry deals with a great variety of different compounds
• Versatility of carbon


  • Atomic number = 6
  • Six protons and six electrons
  • 4 valence electrons
  • Forms 4 non-polar bonds (usually covalent)
  • Arrangement of bonds is a tetrahedral shape
• Functions of proteins


  • Enzymes—catalytic proteins
  • Defensive proteins (e.g., antibodies)
  • Hormonal and regulatory proteins—control physiological processes
  • Receptor proteins—receive and respond to molecular signals
  • Storage proteins store amino acids
  • Structural proteins provide physical stability and movement
  • Transport proteins carry substances within the organism (e.g., hemoglobin)
  • Genetic regulatory proteins regulate when, how, and to what extent a gene is expressed
• Covalent bonds


  • Single—sharing 1 pair of electrons
  • Double—sharing 2 pairs of electrons
  • Triple—sharing 3 pairs of electrons
• Polypeptide chain


  Single, unbranched chain of amino acids
• The length, angle, and direction of bonds between any two elements are always the same
• Proteins can consist of more than one type of polypeptide chain
• Methane


  • Always forms a tetrahedron
• Hemoglobin has 4 distinct polypeptide chains that are folded separately and come together to make the functional protein
• Molecules in living organisms


  • Proteins
  • Carbohydrates
  • Lipids
  • Nucleic acids
• Amino acids


  Have carboxyl and amino groups—so they function as both acid and base
• Living organisms are carbon-based. The 4 classes of biological molecules all contain large numbers of carbon atoms
• Amino acid isomeric forms


  • D-amino acids (dextro, "right")
  • L-amino acids (levo, "left")—this form is found in organisms
• Monomers


  Smaller molecules from which larger molecules are made
• The side chains or R-groups of amino acids also have functional groups
• Biological molecules


  • Proteins: combinations of 20 amino acids
  • Carbohydrates: sugar monomers (monosaccharides) are linked to form polysaccharides
  • Nucleic acids: 4 kinds of nucleotide monomers
  • Lipids: noncovalent forces maintain interactions between lipid monomers
• Amino acids can be grouped based on side chains
• Biochemical unity: the four kinds of macromolecules are present in roughly the same proportions in all living organisms, and have similar functions