Chapter 2: Chemical Compounds and Biological Macromolecules in Anatomy & Physiology

Chemical Compounds in Living Systems

Inorganic vs. Organic Compounds

Living organisms are composed of both inorganic and organic compounds, each playing distinct roles in cellular structure and function.

• Inorganic Compounds: Typically do not contain carbon. Examples include water, salts, acids, and bases. Note: Some exceptions exist, such as carbon dioxide (CO2).

• Organic Compounds: Always contain carbon and are usually larger, more complex molecules. Examples include carbohydrates, lipids, proteins, and nucleic acids.

Water: The Universal Solvent

Properties and Biological Importance

Water is the most abundant inorganic compound in living organisms and is essential for life due to its unique properties.

• High Heat Capacity: Water can absorb and release large amounts of heat with little temperature change, helping to stabilize body temperature.

• High Heat of Vaporization: Evaporation of water requires significant energy, allowing for effective cooling (e.g., sweating).

• Universal Solvent: Water's polarity enables it to dissolve many substances, facilitating chemical reactions and transport.

• Medium for Chemical Reactions: Most biochemical reactions occur in aqueous environments.

Water as a Solvent

• Hydrophilic Substances: Polar molecules and ions dissolve readily in water.

• Hydrophobic Substances: Nonpolar molecules (e.g., fats, oils) do not dissolve in water.

• Amphipathic Molecules: Molecules with both hydrophilic and hydrophobic regions (e.g., phospholipids) can interact with water and lipids.

Biological Macromolecules

Elements and Structure

Macromolecules are large, complex molecules essential for life, composed primarily of carbon (C), hydrogen (H), and oxygen (O), with some also containing nitrogen (N), phosphorus (P), and sulfur (S).

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Polymers and Monomers

Most biological macromolecules are polymers, which are long chains of repeating units called monomers.

• Monomer: The basic building block of a polymer.

• Polymerization: Formation of polymers by joining monomers through dehydration synthesis reactions.

• Dehydration Synthesis: Monomers are joined by removing a water molecule.

• Hydrolysis: Polymers are broken down into monomers by adding water.

Equations:

• Dehydration Synthesis: $\text{Monomer} + \text{Monomer} \rightarrow \text{Polymer} + H_2O$

• Hydrolysis: $\text{Polymer} + H_2O \rightarrow \text{Monomer} + \text{Monomer}$

Dehydration Synthesis and Hydrolysis (Visual Summary)

Process	Description	Example
Dehydration Synthesis	Joins monomers by removing water (OH from one, H from another)	Formation of sucrose from glucose and fructose
Hydrolysis	Breaks polymers by adding water (OH to one, H to another)	Breakdown of sucrose into glucose and fructose

Carbohydrates

Structure and Types

Carbohydrates are hydrophilic molecules with the general formula $(CH_2O)_n$, where n is the number of carbon atoms. They serve as energy sources and structural components.

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

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

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

Examples and Applications:

• Glucose: Primary energy source for cells

• Glycogen: Storage form of glucose in animals

• Starch: Storage form of glucose in plants

• Cellulose: Structural component in plant cell walls

Additional info: Carbohydrates are classified based on the number of sugar units: monosaccharides (one), disaccharides (two), and polysaccharides (many).