Chapter 4 Carbon and the Molecular Diversity of Life

Ch 4 Carbon and the Molecular Diversity of Life What is organic chemistry? Branch of chemistry that studies carbon compounds

Ch 4 Carbon and the Molecular Diversity of Life What is organic chemistry? What do you know about carbon? Atomic # = 6 Forms covalent bonds Tetravalent – 4 valence electrons – forms 4 bonds Tetravalence makes large, complex molecules possible. Determines 3D shape of molecules Compatible with other abundant elements H O N C Hydrogen (valence = 1) Oxygen (valence = 2) Nitrogen (valence = 3) Carbon (valence = 4) This is also the number of covalent bonds each element can form!!!!

Ch 4 Carbon and the Molecular Diversity of Life What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? Carbon skeletons – covalent bonds that link C atoms together & form the skeletal framework of organic molecules

Figure 4.5 Variations in carbon skeletons H (a) Length H C Ethane Propane (b) Branching 2-methylpropane (commonly called isobutane) Butane (c) Double bonds 1-Butene 2-Butene (d) Rings H C Cyclohexane Benzene

Ch 4 Carbon and the Molecular Diversity of Life What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? What are hydrocarbons? Molecules consisting of only hydrogen & carbon Fossil fuels Some are biologically important (fats) Hydrophobic (non-polar) – oil & water don’t mix

Ch 4 Carbon and the Molecular Diversity of Life What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? What are hydrocarbons? What are isomers? - compounds w/ the same molecular formula but w/ different structures & therefore, different properties

Figure 4.7 Three types of isomers CO2H CH3 NH2 C X (a) Structural isomers (b) Geometric isomers (c) Enantiomers L isomer D isomer

Ch 4 Carbon and the Molecular Diversity of Life What is organic chemistry? What do you know about carbon? How does carbon contribute to molecular diversity? What are hydrocarbons? What are isomers? What are functional groups? Parts of molecules involved in chemical rxns Molecules added to carbon skeletons that give properties to the macromolecule….carbs, proteins, lipids, nucleic acids

Figure 4.10 Exploring some important FUNCTIONAL GROUP (may be written HO ) HYDROXYL CARBONYL CARBOXYL OH In a hydroxyl group (—OH), a hydrogen atom is bonded to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH–.) STRUCTURE The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond. When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (—COOH). C O FUNCTIONAL PROPERTIES  Is polar as a result of the electronegative oxygen atom drawing electrons toward itself.  Attracts water molecules, helping dissolve organic compounds such as sugars (see Figure 5.3).  A ketone and an aldehyde may be structural isomers with different properties, as is the case for acetone and propanal.  Has acidic properties because it is a source of hydrogen ions. The covalent bond between oxygen and hydrogen is so polar that hydrogen ions (H+) tend to dissociate reversibly; for example,  In cells, found in the ionic form, which is called a carboxylate group. H O + H+ Acetic acid Acetate ion Figure 4.10 Exploring some important functional groups of organic compounds

Methyl group (-CH3) non-polar FUNCTIONAL PROPERTIES FUNCTIONAL GROUP AMINO SULFHYDRYL PHOSPHATE H SH O N (may be written HS ) O P O H OH STRUCTURE The amino group (—NH2) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton. The sulfhydryl group consists of a sulfur atom bonded to an atom of hydrogen; resembles a hydroxyl group in shape. In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P . The phosphate group (—OPO32–) is an ionized form of a phosphoric acid group (—OPO3H2; note the two hydrogens).  Acts as a base; can pick up a proton from the surrounding solution:  Two sulfhydryl groups can interact to help stabilize protein structure (see Figure 5.20).  Makes the molecule of which it is a part an anion (negatively charged ion). Can transfer energy between organic molecules. FUNCTIONAL PROPERTIES H H N +N H Methyl group (-CH3) non-polar H H (nonionized) (ionized)  Ionized, with a charge of 1+, under cellular conditions.