Chapter 2: Biological Macromolecules: Organic Compounds, Functional Groups, Polymers, and Reactions

Organic Compounds and Functional Groups

Introduction to Organic Chemistry

Organic chemistry is the study of compounds containing carbon, which forms the foundation of biological molecules essential for life. Carbon's unique properties allow it to form diverse structures and complex molecules.

• Organic compounds are molecules primarily composed of carbon atoms bonded with hydrogen, oxygen, nitrogen, sulfur, and other elements.

• Carbon atoms have four valence electrons, enabling them to form four covalent bonds and create chains, branched molecules, and rings.

• Major categories of carbon compounds in biology: Carbohydrates, Lipids, Proteins, and Nucleic acids.

Functional Groups in Organic Molecules

Functional groups are clusters of atoms attached to the carbon backbone that determine many properties and reactivity of organic molecules.

• Hydroxyl group (-OH): Found in sugars and alcohols; increases solubility in water.

• Methyl group (-CH3): Found in fats, oils, steroids, and amino acids; affects molecular shape and function.

• Carboxyl group (-COOH): Present in amino acids and sugars; acts as an acid by donating H+.

• Amino group (-NH2): Found in amino acids and proteins; acts as a base by accepting H+.

• Phosphate group (-PO4): Found in nucleic acids and ATP; involved in energy transfer.

Name & Symbol	Structure	Occurs in
Hydroxyl (-OH)	O-H	Sugars, alcohols
Methyl (-CH3)	C-H3	Fats, oils, steroids, amino acids
Carboxyl (-COOH)	C=O, O-H	Amino acids, sugars, proteins
Amino (-NH2)	N-H2	Amino acids, proteins
Phosphate (-PO4)	P-O4	Nucleic acids, ATP

Polymers and Monomers

Definition and Biological Importance

Polymers are large organic molecules made of repeating units called monomers. They are essential for the structure and function of cells and tissues.

• Monomers: Small, identical or similar subunits (e.g., glucose, amino acids, nucleotides).

• Polymers: Chains of monomers (e.g., starch is a polymer of glucose).

• Examples: Proteins (polymers of amino acids), Polysaccharides (polymers of sugars), Nucleic acids (polymers of nucleotides).

Polymerization: Dehydration Synthesis and Hydrolysis

Polymers are formed and broken down by specific chemical reactions:

• Dehydration synthesis (condensation): Monomers covalently bond to form polymers, releasing water as a by-product. Equation: $\text{Monomer}_1 + \text{Monomer}_2 \rightarrow \text{Polymer} + H_2O$

• Hydrolysis: Polymers are broken down into monomers by the addition of water, which splits the covalent bond. Equation: $\text{Polymer} + H_2O \rightarrow \text{Monomer}_1 + \text{Monomer}_2$

Example: Formation and Breakdown of a Disaccharide

• Dehydration synthesis joins two monosaccharides (e.g., glucose + fructose) to form sucrose and water.

• Hydrolysis splits sucrose into glucose and fructose using water.

Visual Representation of Reactions

Dehydration synthesis and hydrolysis are illustrated by the joining and splitting of monomers, with water as a key reactant or product.

• In dehydration synthesis, an -OH group is removed from one monomer and an H+ from another, forming water.

• In hydrolysis, water is added, and the molecule ionizes into OH- and H+, which are added to the separated monomers.

Summary Table: Key Concepts

Concept	Description	Example
Organic Compound	Molecule containing carbon	Glucose, DNA
Functional Group	Cluster of atoms affecting properties	Carboxyl in amino acids
Monomer	Single subunit	Glucose, amino acid
Polymer	Chain of monomers	Starch, protein
Dehydration Synthesis	Joins monomers, releases water	Formation of maltose
Hydrolysis	Breaks polymers, uses water	Digestion of starch

Additional info:

• These notes cover foundational biochemistry relevant to Anatomy & Physiology, focusing on the molecular basis of biological structure and function.

• Further study will include specific macromolecules (carbohydrates, lipids, proteins, nucleic acids) and their roles in cellular processes.