Organic Chemistry in Biology

Organic Chemistry: The Origin of Life

Organic chemistry is the study of compounds that contain carbon. It is fundamental to understanding biological molecules and the origin of life on Earth.

• Organic compounds range from simple molecules to very large molecules.

• Complex molecules contain carbon-carbon bonds.

• Stanley Miller's experiment demonstrated the abiotic synthesis of organic compounds, suggesting that life could have originated from non-living chemical processes.

Additional info: Abiotic synthesis refers to the formation of organic molecules without biological intervention, possibly under early Earth conditions.

Carbon: Structure and Bonding

Carbon atoms can form diverse molecules by bonding to four other atoms, allowing for a wide variety of organic molecules.

• The major elements of life (C, H, O, N, S, P) are similar in all organisms.

• Carbon can form four bonds, enabling complex molecular structures.

• Each carbon bonded to four other atoms forms a molecule with a tetrahedral shape.

• When two carbon atoms are joined by a double bond, the atoms joined to the carbons are in the same plane as the carbons.

• Carbon atoms can form chains known as carbon skeletons, which are the basis of most organic molecules.

• Carbon chains vary in length and shape.

Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen. They are nonpolar and hydrophobic.

Isomers

Isomers are molecules that contain the same atoms but have those atoms arranged in a different pattern, resulting in different properties.

• Structural isomers: Same atoms, different arrangement.

• Geometric isomers (cis-trans isomers): Same atoms, different spatial arrangement around a double bond.

• Enantiomers: Mirror images of each other, requiring an asymmetric carbon.

Additional info: Enantiomers can have dramatically different biological activities due to their three-dimensional shapes.

Functional Groups in Organic Molecules

Functional Groups: Key to Molecular Function

Distinctive properties of organic molecules depend on the carbon skeleton and the chemical groups, known as functional groups, attached to it. Functional groups are commonly involved in chemical reactions and give molecules unique properties.

• The number and arrangement of functional groups give each molecule its unique molecular architecture and properties.

Major Functional Groups in Biology

The seven functional groups most important in the chemistry of life are:

Functional Group Properties and Examples

• Hydroxyl Group: Polar, forms hydrogen bonds with water, found in alcohols.

• Carbonyl Group: Polar, can be a ketone or aldehyde, found in sugars.

• Carboxyl Group: Polar, acts as an acid, found in carboxylic acids.

• Amino Group: Polar, acts as a base, found in amines.

• Sulfhydryl Group: Nonpolar, can form disulfide bridges in proteins, found in thiols.

• Phosphate Group: Polar, negative charge, component of high energy molecules such as ATP.

• Methyl Group: Nonpolar, affects gene expression when attached to DNA.

ATP: Energy for Cellular Processes

Adenosine triphosphate (ATP) is an important organic phosphate that stores potential energy for cellular processes.

• ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups.

• ATP stores potential energy; its hydrolysis releases energy that can be used by cells.

Equation for ATP hydrolysis:

Summary Table: Functional Groups and Their Properties

Additional info: Functional groups are critical for the structure and function of biomolecules, influencing reactivity, solubility, and interactions within cells.