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.