Chapter 4 Notes: Carbon and Molecular Diversity

Carbon: The Backbone of Life

  • Carbon's ability to form large, complex molecules is unparalleled.
  • Organic compounds contain carbon; organic chemistry studies these molecules.
  • Carbon forms single or double covalent bonds, branching to four other atoms.
  • Four single covalent bonds result in a tetrahedral arrangement.
  • Two carbon atoms forming a double bond create a flat plane.

Carbon Skeletons

  • Carbon chains form the skeleton of most biological molecules.
  • Skeletons vary in:
    • Length
    • Branching
    • Double bond presence
    • Rings

Isomers

  • Isomers: Same number/types of atoms, different structures.
    • Structural isomers: Differ in covalent bonding arrangements (same molecular formula, different arrangement).
    • Cis-trans isomers: Differ in arrangement around a double bond.
    • Cis: "Xs" on the same side.
    • Trans: "Xs" on opposite sides.
    • Enantiomers: Mirror images, possible with carbon attached to four different atoms.

Functional Groups

  • Functional groups influence molecule properties (polarity, bonding, shape, function).
  • Seven important groups:
    • Hydroxyl: (−OH)(-OH), polar, alcohols.
    • Carbonyl: (C=O)(C=O), polar.
    • Aldehydes: at the end of the molecule.
    • Ketones: in the interior of the molecule.
    • Carboxyl: (COOH)(COOH), polar, can be negatively charged (acids).
    • Amino: (NH2)(NH_2), polar or positively charged.
    • Sulfhydryl: (−SH)(-SH), forms cross-links (Thiols).
    • Methyl: (−CH3)(-CH_3), nonpolar, affects gene expression (Methylated compound).
    • Phosphate: (PO4)(PO_4), negatively charged.

ATP

  • ATP (adenosine triphosphate): energy-carrying molecule; removing a terminal phosphate releases energy.