Chemical Reactions and Organic Chemistry: Structure and Function of Biological Molecules

Organic Compounds

Definition and Importance

Organic compounds are molecules that contain carbon and are fundamental to all living organisms. Carbon's unique ability to form large and diverse molecules underlies the complexity of biological systems.

• Key Biological Molecules:

  • Carbohydrates

  • Lipids

  • Proteins

  • Nucleic acids

• Carbon's Electron Configuration: Carbon has four electrons in its outer shell and forms four covalent bonds to achieve a stable octet.

• Example: Methane (CH4) demonstrates carbon's tetrahedral bonding structure.

Hydrocarbons and Carbon Skeletons

Hydrocarbons are organic compounds composed only of carbon and hydrogen. The arrangement of carbon atoms forms the molecule's carbon skeleton, which can be branched or unbranched.

• Unbranched Skeleton: Example: butane

• Branched Skeleton: Example: isobutane

• Isomers: Molecules with the same chemical formula but different connectivity (structure) are called isomers. Isomers have distinct chemical properties due to their shapes.

Functional Groups

Role and Types

Functional groups are specific groups of atoms attached to the carbon skeleton of organic molecules. They determine the molecule's unique chemical properties and reactivity.

• Polar Functional Groups: Groups containing oxygen or nitrogen are typically polar, making molecules hydrophilic (water-loving).

• Water Solubility: The polarity of functional groups is crucial for biological function, as it often makes molecules water soluble.

Functional Group	Structure	Example	Properties
Hydroxyl	-OH	Ethanol	Polar, forms alcohols
Carbonyl	-C=O	Aldehyde, Ketone	Polar, found in sugars
Carboxyl	-COOH	Carboxylic acid	Acidic, ionizes in solution
Amino	-NH2	Amines	Basic, found in amino acids
Phosphate	-PO4	ATP	Energy transfer, acidic
Methyl	-CH3	Methylated compounds	Non-polar, affects shape

Specific Functional Groups

• Methyl Group: Non-polar and non-reactive, but influences molecular shape and function.

• Hydroxyl Group: Composed of a hydrogen atom bonded to an oxygen atom, which is then attached to a carbon skeleton. Molecules with hydroxyl groups are called alcohols. Example: Ethanol

• Carbonyl Group: Consists of a carbon atom double-bonded to an oxygen atom.

  • If at the end of a chain: Aldehyde

  • If within the chain: Ketone

  • Sugars often contain carbonyl and hydroxyl groups.

• Carboxyl Group: Carbon double-bonded to oxygen and single-bonded to a hydroxyl group. Behaves as an acid, ionizing and donating H+ to solution. Compounds: Carboxylic acids

• Amino Group: Nitrogen bonded to two hydrogens and a carbon skeleton. Acts as a base by picking up H+ from solution. Compounds: Amines; amino acids contain both amino and carboxyl groups.

• Phosphate Group: Phosphorus atom bonded to four oxygen atoms, attached to the carbon skeleton by one oxygen. Involved in energy transfer (e.g., ATP).

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