TS

Essentials of Biology - Carbon and Organic Molecules

Organic Molecules

  • Contain carbon and hydrogen.
  • Biological molecules are organic.
  • Inorganic molecules lack carbon and hydrogen.

Carbon

  • Forms macromolecules: proteins, nucleic acids (RNA and DNA), carbohydrates, and lipids.
  • Forms covalent bonds with up to four atoms.

Carbon Atom

  • Has 6 electrons, 4 in outer shell.
  • Bonds with C, H, N, O, P, S.
  • Forms stable carbon-carbon bonds, enabling large chains.

Hydrocarbons

  • Organic molecules of carbon and hydrogen (e.g., methane CH_4).
  • Form branched/unbranched chains or rings.
  • Store energy, released upon oxidation.

Hydrocarbon Chains

  • Aliphatic hydrocarbons: linear carbon chains.
  • Suffixes denote carbon-carbon bonds: "-ane" (single), "-ene" (double), "-yne" (triple).

Hydrocarbon Rings

  • Aromatic hydrocarbons: closed rings (e.g., benzene).
  • May have double bonds.
  • Can be both aliphatic and aromatic portions.

Isomers

  • Molecules with the same formula but different structures.
  • Structural isomers: different covalent bond placement (e.g., butane vs. isobutene, C4H{10}).

Geometric Isomers

  • Differ in bond arrangement around double bonds.
  • * trans configuration: groups on opposite sides, linear structure.
  • * cis configuration: groups on same side, bend the carbon backbone.

Unsaturated Fats

  • Contain double bonds.
  • Cis bonds cause bending, resulting in liquid oils.
  • Trans fats have linear fatty acids and form solid fats.

Saturated fats

  • No double bonds, contain maximum hydrogen.
  • Solid at room temperature, usually animal origin.

Enantiomers

  • Non-superimposable mirror images.
  • Example: amino acid alanine; L-forms make proteins; D-forms in bacterial cell walls.
  • D-glucose is a product of photosynthesis.

Common Functional Groups

  • Atoms within molecules that confer specific properties.
  • Attached to carbon backbone.
  • Proteins, lipids, carbohydrates, and nucleic acids each have characteristic sets.

Functional Groups (Hydrophobic/Hydrophilic)

  • Classified by charge/polarity.
  • Methyl (CH_3) is hydrophobic.
  • Carboxyl (COOH) is hydrophilic.

Impact of functional groups

  • Hydrocarbons are nonpolar and hydrophobic.
  • Glucose (with hydroxyl groups) is hydrophilic.
  • Carboxyl groups are polar, weak acids (-COOH \rightarrow -COO^- + H^+).

Hydrogen Bonds

  • Important for macromolecule folding and shape.
  • Examples: DNA base pairing, enzyme-substrate binding.