BIOL 111 Chapter 4

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Carbon

Most organic molecules have a carbon skeleton (chains, rings, etc.; very diverse)
- varied lengths of carbon chains
- varied positioning and number of double bonds
- varied branching of two or more chains
- varied hexagonal ring positioning of 6 carbon atoms
4 bonding points (valence = 4) in tetrahedral pattern
Hydrocarbons = oodles of hydrogen + oodles of carbon = oodles of energy

Same chemical formula, different ways to arrange atoms structurally.

EX: C₅H₁₂ can be arranged three ways

Structural Isomers: different bonds between atoms (i.e. C can be bonded to 2 H and 1 C in one molecule or 3 C and 1 H in a different molecule)
Geometric Isomers: same bonds between atoms, but different orientation (i.e. C is always bound to 1 C, 1 H, and 1 X for all molecules, but Xs can be on same side (cis) or opposite (trans))
Enantiomers: mirror-images: left- (L) and right- (D) handed molecules; mirrored around asymmetric carbon atom.

Common patterns among organic compounds: (most are bound to carbon atoms)

Carbonyl (CAR-bo-NEEL): >CO (carbon double-bonded with oxygen); Polar in sugars

Carboxyl: Carbonyl + Hydroxyl; —COOH (carbon has two oxygen: one is double bound, other is single; single-bond oxygen has hydrogen); Polar (hydrophilic), always acidic due to OH^– (see BIOL 111 Chapter 3; found in amino acids and fatty acids

Amino: —NH₂ (nitrogen with two hydrogens); polar, acts as a base on pH scale; picks up an extra H⁺ ion

Sulfhydryl: —SH or HS—; In some amino acids; Important to protein structure

Phosphate: —OPO₃^2–; EX: Cell gets energy from adenosine triphosphate (ATP); Very polar; Negatively charged; Found in nucleic acids, ATP, and phospholipids

Methyl: —CH₃ (carbon with three hydrogens); Addition to DNA/other molecules affects function of that molecule (more or less reactive; turns genes on or off)