The Chemistry of Life: Organic Compounds in Anatomy & Physiology

The Chemistry of Life

Introduction

This section introduces the foundational chemical principles underlying human anatomy and physiology, focusing on the major classes of organic compounds essential for life: carbohydrates, lipids, proteins, and nucleic acids. Understanding these molecules is crucial for comprehending cellular structure, metabolism, and physiological processes.

Organic Compounds: Hydrocarbons

Definition and Structure

• Hydrocarbons are organic compounds composed exclusively of carbon (C) and hydrogen (H) atoms.

• They exist as chains (linear or branched) and rings (cyclic structures).

• Hydrocarbons form the backbone of more complex organic molecules found in living organisms.

Example: The hexagon symbol represents a six-carbon ring (benzene), where each corner is a carbon atom and hydrogen atoms are implied but not shown.

Monomers and Polymers

Basic Concepts

• The human body contains four major classes of organic compounds: Carbohydrates, Lipids, Proteins, and Nucleic Acids.

• Monomers are single subunits that can be joined to form larger molecules.

• Polymers are large molecules made by linking many monomers together.

• Dehydration Synthesis is a chemical reaction that joins two monomers by removing a molecule of water.

• Hydrolysis Reaction breaks a polymer into monomers by adding a molecule of water.

Example: Glucose monomers join to form starch or glycogen via dehydration synthesis; these polymers can be broken down by hydrolysis.

Carbohydrates

Overview and Classification

• Carbohydrates are composed of carbon, hydrogen, and oxygen, typically in a 1:2:1 ratio (C:H:O).

• They are polar and hydrophilic (water-soluble).

• Primary function: serve as fuel; some have structural roles.

• Monosaccharides are simple sugars (single monomer units).

• Disaccharides consist of two monosaccharides joined together.

• Polysaccharides are long chains of monosaccharides.

• Glycoproteins and Glycolipids are carbohydrates covalently bonded to proteins and lipids, important for cell recognition and communication.

Monosaccharides

• Contain 3 to 7 carbon atoms.

• Common examples: Glucose (C6H12O6), Fructose, Galactose, Ribose, and Deoxyribose.

• Glucose is the primary energy source for cells.

Disaccharides

• Formed by joining two monosaccharides via dehydration synthesis.

• Examples: Sucrose (table sugar, glucose + fructose), Lactose (milk sugar, glucose + galactose).

• Can be broken down into monosaccharides by hydrolysis.

Polysaccharides

• Composed of many monosaccharide units linked together.

• Starch: storage form of glucose in plants.

• Glycogen: storage form of glucose in animals (liver and skeletal muscle).

• Highly branched structures allow rapid release of glucose when needed.

Summary Table: Types of Carbohydrates

Type	Structure	Example	Function
Monosaccharide	Single sugar unit	Glucose, Fructose	Energy source
Disaccharide	Two sugar units	Sucrose, Lactose	Transport, energy
Polysaccharide	Many sugar units	Starch, Glycogen	Energy storage