Chapter 4: Carbon and the Diversity of Life Organic molecules: molecules that contain carbon Carbon: valence of 4 form 4 covalent bonds Variations in carbon skeletons contribute to the diversity of organic molecules.

Hydrocarbons: molecules containing only carbon and hydrogen -are hydrophobic and nonpolar Major component of many Lipids (fats)

Isomers compounds with the same molecular formula but with different structures (hence different properties)

Three types of isomers [Figure 4.6] Structural isomers – covalent partners Geometric isomers – rearrangement around double bond (rhodopsin) Enantiomers – 3-D shape /mirror image - require asymmetric carbons

Functional Groups contribute to molecular diversity and behave consistently from one organic molecule to another

Hydroxyl Group – consists of a hydrogen atom bonded to an oxygen atom, which in turn is bonded to carbon (-OH)  Contributes polarity  Organic compounds with hydroxyl groups are called alcohols

Carbonyl Group – consists of a carbon atom double bonded to an oxygen (-C=O)  Contributes polarity  A functional group found in sugars  aldehyde(“hides at end”) or ketone (“right at home, mixing in)

Carboxyl Group consists of a carbon atom which is both double- bonded to an oxygen and single-bonded to a hydroxyl group (-COOH)  Contributes polarity  hydrogen reversibly dissociates as H + (acidic properties).  Compounds with this functional group are called carboxylic acids.

Amino Group – consists of a nitrogen atom bonded to two hydrogens and to the carbon skeleton (-NH2).  Contributes polarity  Acts as a weak base. The unshared pair of electrons on the nitrogen can accept a proton, giving the amino group a +1 charge.  Organic compounds with this functional group are called amines.

Sulfhydryl Group – consists of an atom of sulfur bonded to an atom of hydrogen (-SH). * Contributes polarity  Help stabilize the structure of proteins  Organic compounds with this functional group are called thiols.

Phosphate Group – Functional group which is the dissociated form of phosphoric acid (H 3 PO 4 )  (-OPO 3 )  Contributes polarity  The loss of two protons by dissociation leaves the phosphate groups with a negative charge.  Has acidic properties since it loses protons  Organic phosphates are important in cellular energy storage and transfer (i.e., ATP)

Methyl Group – Functional group which consists of a carbon and three hydrogen atoms (-CH 3 )  Nonpolar group (hydrophobic)