Biology 107Biology 107

Carbon and Molecular DiversityCarbon and Molecular Diversity

September 4, 2002September 4, 2002

Organic Molecules Contain CarbonOrganic Molecules Contain Carbon

Valence Shells of Atoms Most Commonly Found in Valence Shells of Atoms Most Commonly Found in Organic MoleculesOrganic Molecules

Majors Types of Majors Types of IsomersIsomers

1.1. Structural isomersStructural isomers

2.2. Geometric isomersGeometric isomers

3.3. Enantiomers (mirror-images)Enantiomers (mirror-images)

Functional Groups

Biological Molecules Usually Have More Than One Biological Molecules Usually Have More Than One Functional GroupFunctional Group

Dehydration Synthesis Reactions - Additions

Hydrolysis Reaction - RemovalsHydrolysis Reaction - Removals

Polymer Synthesis Polymer Synthesis and Breakdown and Breakdown

ReactionsReactions

Synthesis of complex Synthesis of complex molecules from simpler molecules from simpler molecules (molecules (anabolismanabolism) by ) by dehydration synthesis dehydration synthesis reactionsreactions

Break down of complex Break down of complex molecules to simpler molecules to simpler molecules (molecules (catabolismcatabolism) by ) by hydrolysis reactionshydrolysis reactions

Why so many different metabolic Why so many different metabolic enzymes in cells?enzymes in cells?

CarbonCarbonStudent Objectives:Student Objectives: As a result of this lecture and the assigned reading, you should As a result of this lecture and the assigned reading, you should

understand the following:understand the following:

1.1. Role of carbon in life's diversity - next to water, compounds containing carbon are the Role of carbon in life's diversity - next to water, compounds containing carbon are the most common substances in living organisms.most common substances in living organisms.

2.2. The enormous variety of carbon-based molecules is because a carbon atom has 4 outer The enormous variety of carbon-based molecules is because a carbon atom has 4 outer shell electrons in a shell that holds 8.shell electrons in a shell that holds 8.

3.3. Compounds with the same molecular formula but different structure are calledCompounds with the same molecular formula but different structure are called isomers isomers..

CarbonCarbon4.4. The unique properties of an organic compound depend not only The unique properties of an organic compound depend not only

on its carbon skeleton, but also on certain groups of atoms that on its carbon skeleton, but also on certain groups of atoms that are covalently linked to the skeleton. These groups of atoms are are covalently linked to the skeleton. These groups of atoms are called functional groups, the name reflecting the fact that these called functional groups, the name reflecting the fact that these parts of the organic molecules usually are involved in chemical parts of the organic molecules usually are involved in chemical reactions. See Table 4.1 in Campbell reactions. See Table 4.1 in Campbell et alet al..

5.5. Most of these functional groups are polar, because their oxygen Most of these functional groups are polar, because their oxygen or nitrogen atoms are highly electronegative. The polarity tends or nitrogen atoms are highly electronegative. The polarity tends to make compounds containing these groups hydrophilic, and to make compounds containing these groups hydrophilic, and therefore soluble in water - a necessary condition for their roles in therefore soluble in water - a necessary condition for their roles in water-based life. Note that many biological molecules have two water-based life. Note that many biological molecules have two or more functional groups (e.g., amino acids - contain at least one or more functional groups (e.g., amino acids - contain at least one carboxyl as well as one amino group).carboxyl as well as one amino group).

CarbonCarbon

6.6. Organic macromolecules are polymers created through Organic macromolecules are polymers created through dehydration synthesis reactionsdehydration synthesis reactions that chemically link the specific that chemically link the specific monomers together with covalent bonds. Polymers are broken monomers together with covalent bonds. Polymers are broken down through down through hydrolysis reactionshydrolysis reactions..

7.7. It is the variety in polymers that accounts for the uniqueness of It is the variety in polymers that accounts for the uniqueness of each organism; the monomers used to make polymers are each organism; the monomers used to make polymers are essentially universal throughout the biological realm. essentially universal throughout the biological realm.