Structure and Function of Biological Molecules

Chapter 5: Structure and Function of Biological Molecules

Introduction

Biological molecules, also known as biomolecules, are essential for life. They include carbohydrates, lipids, proteins, and nucleic acids. These macromolecules are composed of smaller subunits and play critical roles in structure, function, and regulation within living organisms.

Major Classes of Biological Molecules

Overview of Biomolecules

• Carbohydrates: Serve as fuel and building material.

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

• Proteins: Perform a wide range of functions including catalysis, structure, transport, and regulation.

• Nucleic Acids: Store and transmit genetic information.

Biomolecule Terminology

Monomers, Dimers, and Polymers

• Monomer: A single subunit or building block of a macromolecule.

• Dimer: Two monomers covalently bonded together.

• Polymer: Many monomers covalently bonded together, forming a large molecule.

Enzymes are biological catalysts that help to make and break biomolecules.

Polymerization and Depolymerization

Dehydration Synthesis

Dehydration synthesis is the process by which monomers are covalently bonded together into polymers, with the removal of a water molecule.

• Anabolic process: Builds larger molecules from smaller ones.

• Requires energy input.

• Example: Formation of a disaccharide from two monosaccharides.

$\text{Monomer}_1 + \text{Monomer}_2 \rightarrow \text{Polymer} + \text{H}_2\text{O}$

Hydrolysis

Hydrolysis is the process by which polymers are broken down into monomers, with the addition of a water molecule.

• Catabolic process: Breaks down larger molecules into smaller ones.

• Releases energy.

• Example: Digestion of starch into glucose monomers.

$\text{Polymer} + \text{H}_2\text{O} \rightarrow \text{Monomer}_1 + \text{Monomer}_2$

Macromolecules: Structure and Function

Comparison of Major Macromolecules

The four major classes of macromolecules differ in their monomers, functions, elemental composition, and solubility.

Macromolecule	Monomer	Function(s)	Elements Present	Water Solubility	Examples
Carbohydrates	Monosaccharides	Energy storage, structure	C, H, O	Yes	Glucose, starch, cellulose
Lipids	Glycerol & fatty acids	Energy storage, membranes	C, H, O (sometimes P)	No	Fats, oils, phospholipids
Proteins	Amino acids	Catalysis, structure, transport	C, H, O, N (sometimes S)	Varies	Enzymes, hemoglobin
Nucleic Acids	Nucleotides	Genetic information	C, H, O, N, P	Yes	DNA, RNA

Carbohydrates

Structure and Function

Carbohydrates serve as fuel and building material. They include sugars and polymers of sugars. The simplest carbohydrates are monosaccharides, or single sugars. Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks.

• Elemental composition: C, H, O in a 1:2:1 ratio (e.g., C6H12O6).

• Monosaccharides: Glucose, fructose, galactose.

• Disaccharides: Sucrose, lactose, maltose.

• Polysaccharides: Starch, glycogen, cellulose.

Classification and Nomenclature

Type	Examples	Description
Monosaccharide	Glucose, fructose	Single sugar unit
Oligosaccharide	Maltose, sucrose	2-10 sugar units
Polysaccharide	Starch, cellulose, glycogen	Many sugar units

Structure and Function of Polysaccharides

• Starch: Storage polysaccharide in plants, composed of amylose and amylopectin.

• Glycogen: Storage polysaccharide in animals, highly branched.

• Cellulose: Structural polysaccharide in plant cell walls, composed of β-glucose monomers.

Key Science Skills

• Visual representation/modeling

• Concept explanation

• Argumentation

Summary Table: Macromolecules and Their Properties

Macromolecule	Monomer	Bond Type	Main Function
Carbohydrate	Monosaccharide	Glycosidic linkage	Energy, structure
Lipid	Glycerol + fatty acids	Ester bond	Energy storage, membranes
Protein	Amino acid	Peptide bond	Catalysis, structure
Nucleic Acid	Nucleotide	Phosphodiester bond	Genetic information

Additional info: The notes above expand on the slide content by providing definitions, examples, and context for each macromolecule class, as well as the chemical processes of dehydration synthesis and hydrolysis. The tables are reconstructed and summarized for clarity and completeness.