Organic Molecules in Chemistry

Definition and Classification

Organic molecules are chemical compounds primarily composed of carbon atoms covalently bonded to hydrogen, oxygen, nitrogen, and other elements. They form the basis of living matter and are central to biochemistry and general chemistry.

• Key Elements: CHNOPS (Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur) are the bulk elements in living systems.

• Organic Molecules: Defined as molecules with covalently linked carbon atoms.

• Hydrocarbons: Molecules made only of carbon and hydrogen atoms.

Example: Hydrocarbons include methane (CH4), ethane (C2H6), and benzene (C6H6).

Carbon as a Building Block

Carbon's ability to form four covalent bonds makes it a versatile 'atomic building block' for a wide variety of molecules.

• Backbone Variability: Carbon backbones can vary in length, position of double bonds, branching, and ring forms.

• Structural Diversity: This variability allows for the formation of complex organic molecules.

Example: Carbon chains can be straight, branched, or form rings, as seen in glucose and benzene.

Functional Groups in Organic Chemistry

Definition and Importance

Functional groups are specific groups of atoms within molecules that are responsible for characteristic chemical reactions.

• Reactivity: Functional groups are reactive and commonly found together in organic molecules.

• Extension: They typically extend off the carbon backbone.

• Common Groups: Hydroxyl (-OH), Carbonyl (C=O), Carboxyl (-COOH), Amino (-NH2), Sulfhydryl (-SH), Phosphate (-PO4), and Methyl (-CH3).

Biomolecules: Classes and Structure

Main Classes of Biomolecules

Biomolecules are organic molecules essential for life. There are four primary classes:

• Carbohydrates

• Proteins

• Nucleic Acids

• Lipids

Example: Carbohydrates include glucose; proteins include enzymes; nucleic acids include DNA and RNA; lipids include fats and phospholipids.

Monomers and Polymers

Monomers are individual building blocks that can be linked together to form polymers.

• Polymers: Long chains of monomers linked together.

• Monomer Types: Vary by biomolecule class (e.g., monosaccharides for carbohydrates, amino acids for proteins).

Polymerization Reactions

Polymers are formed and broken down by specific chemical reactions:

• Dehydration Synthesis: Forms covalent bonds between monomers, releasing water.

• Hydrolysis: Breaks covalent bonds by adding water.

Equation:

Carbohydrates: Structure and Function

Definition and General Formula

Carbohydrates are carbon-based molecules hydrated with many hydroxyl groups (-OH). They are commonly referred to as sugars.

• General Formula:

• Simple Carbohydrates: Monosaccharides like glucose ()

• Complex Carbohydrates: Polysaccharides like starch and cellulose

Classification by Size

• Monosaccharides: Single sugar units (e.g., glucose)

• Oligosaccharides: 2-20 covalently linked monosaccharides

• Polysaccharides: Hundreds to thousands of monosaccharides linked

Formation and Breakdown of Polysaccharides

Polysaccharides are formed by dehydration synthesis, linking monosaccharides via glycosidic bonds. Hydrolysis breaks these bonds.

• Glycosidic Bond: Covalent bond between monosaccharides

• Dehydration Synthesis:

• Hydrolysis:

Carbohydrate Functions

Structural Support and Energy Storage

Carbohydrates serve two main functions in living organisms:

• Structural Support: Building materials (e.g., cellulose in plants, chitin in insects)

• Energy Storage: Storage of glucose (e.g., starch in plants, glycogen in animals)

Example: Starch is the main energy storage polysaccharide in plants, while glycogen serves this role in animals.

Additional info: Chitin is also found in the exoskeletons of crustaceans and insects, providing structural support.