Chapter 4. Carbon and the Molecular Diversity of Life. AP Biology Parkway Central H.S. A. Bergeron

Transcription

1 Chapter 4 Carbon and the Molecular Diversity of Life AP Biology Parkway Central.S. A. Bergeron

2 Do Now: ydrocarbons are considered to be hydrophobic molecules. Why are hydrocarbons hydrophobic and not hydrophilic?

3 Organic Chemistry for the Biologist Carbon atoms can form diverse molecules by bonding to four other atoms Carbon has four valence electrons This allows it to form four covalent bonds with a variety of atoms

4 A Carbon Atom s Four Valence Electrons Allow it to Form Chemical Bonds with a Multitude of Different Atoms The electron configuration of carbon gives it covalent compatibility with many different elements ydrogen Oxygen Nitrogen Carbon (valence = 1) (valence = 2) (valence = 3) (valence = 4) O N C Figure 4.4

5 Simple Organic Compounds ow many bonds does each carbon atom form with other atoms? Why?

6 The Structure of Carbon Skeletons Can Vary

7 Isomers Molecules with the same molecular formula but different structures and properties Three types of isomers typically found in Biology are: Structural Geometric Enantiomers (a) Structural isomers (b) Geometric isomers C C C C C X C C C C C C C X C C X CO 2 CO 2 X (c) Enantiomers C C 3 N 2 N 2 C C 3 Figure 4.7 A-C

8 Structural Isomers Molecules can have the same molecular formula (i.e. #atoms, types of atoms) but very different structures

9 Geometric Isomers Cis: atoms and/or functional groups are on the same side of the double bond Trans: atoms and/or functional groups are on opposite sides of the double bond

10 Biological Importance of cis and trans Geometric Isomers Cis-9-octadecenoic acid Trans-9-octadecenoic acid Each of these molecules consists of a long hydrocarbon chain with a carboxylic acid (-COO) group at the end What type of molecule do these two structures represent?

11 Enantiomers/Stereoisomers Asymmetric carbon - a central carbon atom that is connected to four different atoms or functional groups Think of one molecule looking at its reflection in the mirror Use the and Rule to determine handedness of the molecule (I can show you how this works if you want to know)

12 Enantiomers Are important in the pharmaceutical industry Figure 4.8 L-Dopa (effective against Parkinson s disease) D-Dopa (biologically inactive)

13 Functional Groups are the Parts of Molecules Involved in Chemical Reactions Functional groups Are the chemically reactive groups of atoms within an organic molecule Six functional groups are important in the chemistry of life ydroxyl Carbonyl Carboxyl Amino Sulfhydryl Phosphate

14 Functional Groups in Biological Molecules Name!! Structural Formula! Polar/Nonpolar!? Found In ydroxyl! R-O!!! Polar!! Alcohols Carbonyl! R-C=O! (general)! Polar!! Sugars a. Aldehyde!!!! b. Ketone!!!! Carboxyl R-COO!! Polar!! Amino acids Amino!! R-N 2!!! Polar!! Amino acids Phosphate! R-PO 2-4!!! Polar!! DNA, RNA!!!!!!! nucleotides Sulfhydryl! R-S!!! Polar!! Thiols R= Rest of molecule

15 Important Functional Groups of Organic Compounds FUNCTIONAL GROUP YDROXYL! CARBONYL CARBOXYL O (may be written O ) C O C O O STRUCTURE In a hydroxyl group ( O), 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, O.) > The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond. When an oxygen atom is doublebonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group ( COO).

16 Important Functional Groups of Organic Compounds - Examples NAME OF COMPOUNDS EXAMPLE Alcohols (their specific names usually end in -ol) Ketones if the carbonyl group is within a carbon skeleton Aldehydes if the carbonyl group is at the end of the carbon skeleton O Carboxylic acids, or organic acids O C C O Ethanol, the alcohol present in alcoholic beverages C C C Acetone, the simplest ketone C C O Acetic acid, which gives vinegar its sour tatste O C C C Propanal, an aldehyde

17 Important Functional Groups of Organic Compounds AMINO SULFYDRYL POSPATE N S (may be written S ) O O P O O The amino group ( N 2 ) 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 ( OPO 3 2 ) is an ionized form of a phosphoric acid group ( OPO 3 2 ; note the two hydrogens).

18 Important Functional Groups of Organic Compounds - Examples O O O O C C N C C S C C C O P O O O Glycine Ethanethiol Glycerol phosphate Because it also has a carboxyl group, glycine is both an amine and a carboxylic acid; compounds with both groups are called amino acids.

19 1) 3) 4) 5) 2) 6) 7) 8) 9) Briefly explain why the group circled in #3 is protonated. 10) The groups circled in #4 and #6 are classified as

20 Why Are Functional Groups Important? Example - Structural differences btw male and female sex hormones Estrogen Testosterone