General Biology Chapter 3: Organic Chemistry and Biological Molecules

Organic Chemistry in Biology

Introduction to Organic Molecules

Organic chemistry is fundamental to biology, as it explains the structure and function of molecules that make up living organisms. The unique ability of carbon atoms to form four covalent bonds allows for the creation of a vast diversity of organic compounds.

• Organic compounds are molecules primarily composed of carbon and hydrogen.

• Carbon chains form the backbone of most organic molecules, providing structural diversity.

• Isomers are compounds with the same molecular formula but different structures, leading to different properties.

• Hydrocarbons consist only of carbon and hydrogen atoms.

Structural Diversity of Carbon Skeletons

Arrangements of Carbon Atoms

Carbon atoms can be arranged in various ways, resulting in molecules with different shapes and properties. These arrangements include straight chains, branched chains, and rings, as well as the presence of double bonds.

• Straight chains: Examples include ethane and propane, where carbon atoms are connected in a linear sequence.

• Branched chains: Examples include butane and isobutane, where the carbon skeleton branches off.

• Rings: Examples include cyclohexane and benzene, where carbon atoms form closed ring structures.

• Double bonds: Molecules like 1-butene and 2-butene have double bonds that can vary in position, affecting molecular properties.

Types of Isomers

Isomers are molecules with the same chemical formula but different arrangements of atoms. The three main types are:

• Structural isomers: Differ in the covalent arrangement of atoms.

• Geometric isomers: Differ in spatial arrangement around a double bond.

• Enantiomers: Are mirror images of each other, often with different biological activities.

Functional Groups in Organic Molecules

Importance of Functional Groups

Functional groups are specific groups of atoms attached to the carbon skeleton that confer particular chemical properties to organic molecules. The presence and arrangement of these groups determine the molecule's reactivity and function in biological systems.

• Functional groups give organic molecules specific chemical properties and roles in biological processes.

• Six important functional groups commonly found in biological molecules are:

Chemical Group	Structure	Example
Hydroxyl group	-OH	Alcohol
Carbonyl group	-C=O	Carboxylic acid
Carboxyl group	-COOH	Carboxylic acid
Amino group	-NH2	Amine
Phosphate group	-OPO32-	Adenosine
Methyl group	-CH3	Methylated compounds

Additional info: Functional groups are critical in determining the solubility, acidity, and reactivity of organic molecules, influencing processes such as enzyme activity and cell signaling.