Chapter 5: The Structure and Function of Large Biological Molecules (Campbell Biology)

Introduction to Biological Macromolecules

Overview of Macromolecules

Large biological molecules, or macromolecules, are essential for life and include carbohydrates, lipids, proteins, and nucleic acids. Most macromolecules are polymers made from smaller units called monomers, with the exception of lipids. The specific structure of each macromolecule determines its biological function.

• Carbohydrates: Provide energy and structural support.

• Lipids: Function in energy storage, membrane structure, and signaling.

• Proteins: Serve as enzymes, structural components, and signaling molecules.

• Nucleic acids: Store and transmit genetic information.

Key Vocabulary

• Monomer: A small molecule that can join with others to form a polymer.

• Polymer: A long molecule composed of many monomers.

• Dehydration Reaction: Chemical reaction that joins two monomers by removing a water molecule.

• Hydrolysis: Chemical reaction that breaks polymers into monomers by adding water.

• Carbohydrates: Monosaccharides, disaccharides, polysaccharides.

• Lipids: Fats, phospholipids, steroids.

• Proteins: Amino acids, peptide bonds, primary to quaternary structure.

• Nucleic acids: DNA, RNA, nucleotides.

The Synthesis and Breakdown of Polymers

Polymer Formation and Degradation

Polymers are formed and broken down by specific chemical reactions, often catalyzed by enzymes.

• Dehydration Reaction: Joins two monomers by removing a water molecule.

• Hydrolysis: Breaks a polymer into monomers by adding water; essentially the reverse of dehydration.

• Enzymes: Specialized proteins that speed up these reactions.

Carbohydrates

Classification and Functions

Carbohydrates are sugars and their polymers, serving as energy sources and structural materials.

• Monosaccharides: Simple sugars (e.g., glucose, fructose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose, lactose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose, chitin).

• Functions: Energy storage (starch, glycogen), structural support (cellulose in plants, chitin in fungi and arthropods).

Sugars: Structure and Classification

Monosaccharides have molecular formulas that are usually multiples of CH2O. Glucose ($C_6H_{12}O_6$) is the most common monosaccharide. Classification is based on:

• The location of the carbonyl group (aldose or ketose).

• The number of carbons in the carbon skeleton (triose, pentose, hexose).

Table: Classification of Monosaccharides

Type	Aldoses (Aldehyde Sugars)	Ketoses (Ketone Sugars)
Triose (3C)	Glyceraldehyde	Dihydroxyacetone
Pentose (5C)	Ribose	Ribulose
Hexose (6C)	Glucose, Galactose	Fructose

Linear and Ring Forms of Sugars

Monosaccharides can exist in both linear and ring forms. In aqueous solutions, sugars often form rings, which are more stable.

• Ring formation involves a reaction between the carbonyl group and a hydroxyl group.

• Example: Glucose forms a six-membered ring in solution.

Disaccharides

A disaccharide is formed when a dehydration reaction joins two monosaccharides. The covalent bond formed is called a glycosidic linkage.

• Example: Maltose (glucose + glucose), Sucrose (glucose + fructose).

Polysaccharides

Polysaccharides are polymers of sugars with storage and structural roles. Their architecture and function are determined by their sugar monomers and the positions of glycosidic linkages.

• Storage Polysaccharides: Starch (plants), Glycogen (animals).

• Structural Polysaccharides: Cellulose (plants), Chitin (fungi, arthropods).

Table: Major Polysaccharides and Their Functions

Polysaccharide	Organism	Function
Starch	Plants	Energy storage
Glycogen	Animals	Energy storage
Cellulose	Plants	Structural support (cell wall)
Chitin	Fungi, Arthropods	Structural support (exoskeleton, cell wall)

*Additional info: Further details on lipids, proteins, and nucleic acids are present in the full notes but not shown in the provided images. The above content covers the first half of the chapter, focusing on carbohydrates and polymer chemistry. For a complete study guide, include similar structured notes for lipids, proteins, and nucleic acids as outlined in the text.*