Lecture #1

Course Introduction: BIOL 325 Physiology

Overview of Course Content

This course provides a foundational understanding of human physiology, focusing on the chemical and cellular basis of life, neural and hormonal control systems, and the coordination of body functions. The course is designed for students pursuing studies in Anatomy & Physiology and related health sciences.

• Basic Cell Physiology: Study of cell structure, function, and the chemical processes essential for life.

• Neural and Hormonal Control Systems: Examination of how the nervous and endocrine systems regulate body functions.

• Coordinated Body Functions: Exploration of how different organ systems work together to maintain homeostasis.

Lecture #1: Introduction and Chemistry

Chemistry Overview in Physiology

Chemistry is fundamental to understanding physiological processes. This section introduces the distinction between organic and inorganic molecules, as well as the concepts of hydrophilicity, hydrophobicity, and amphiphilicity.

Organic vs. Inorganic Molecules

• Organic Molecules: Contain carbon and hydrogen, often large and complex (e.g., proteins, lipids, nucleic acids, carbohydrates).

• Inorganic Molecules: Generally do not contain both carbon and hydrogen; include water, salts, acids, bases, and gases (e.g., O2, CO2).

• Electrolytes: Inorganic ions such as Na+, K+, Cl-, Ca2+, which are essential for nerve impulse transmission and muscle contraction.

Example: Glucose (C6H12O6) is an organic molecule, while sodium chloride (NaCl) is inorganic.

Hydrophilic, Hydrophobic, and Amphiphilic Molecules

• Hydrophilic: "Water-loving" molecules that dissolve easily in water; typically polar or charged (e.g., salts, sugars).

• Hydrophobic: "Water-fearing" molecules that do not dissolve in water; typically nonpolar (e.g., fats, oils).

• Amphiphilic (Amphipathic): Molecules with both hydrophilic and hydrophobic regions (e.g., phospholipids in cell membranes).

Example: Phospholipids have hydrophilic heads and hydrophobic tails, allowing them to form the bilayer structure of cell membranes.

Key Chemical Bonds in Physiology

Types of Chemical Bonds

Chemical bonds are essential for assembling atoms into molecules and enabling chemical interactions in the body.

• Ionic Bonds: Formed by the transfer of electrons between atoms, resulting in charged ions (e.g., Na+ and Cl- in NaCl).

• Covalent Bonds: Formed by the sharing of electrons between atoms; can be nonpolar (equal sharing) or polar (unequal sharing).

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).

• Hydrophobic Interactions: Nonpolar molecules aggregate to avoid water, important in protein folding and membrane structure.

Example: Water molecules are held together by hydrogen bonds, contributing to water's unique properties.

Major Causes of Death (Contextual Relevance)

Leading Causes of Death in the United States

Understanding the major causes of death provides context for the importance of physiological health and disease prevention.

Cause of Death
Heart disease
Cancer
COVID-19
Accidents
Stroke
Chronic lower respiratory disease
Alzheimer’s disease
Diabetes
Other respiratory
Kidney disease

Application: Many of these diseases are linked to physiological dysfunctions at the cellular or molecular level, highlighting the importance of understanding physiology.

Summary Table: Properties of Molecules

Property	Hydrophilic	Hydrophobic	Amphiphilic
Solubility in Water	High	Low	Variable (depends on region)
Examples	Salts, sugars	Fats, oils	Phospholipids
Role in Physiology	Transport, metabolism	Membrane structure, energy storage	Membrane formation, signaling

Key Terms and Definitions

• Physiology: The study of the functions and mechanisms occurring in living organisms.

• Anatomy: The study of the structure of organisms and their parts.

• Homeostasis: The maintenance of a stable internal environment.

• Macromolecule: A large, complex molecule such as a protein, nucleic acid, carbohydrate, or lipid.

• Electrolyte: A substance that dissociates into ions in solution and is capable of conducting electricity.

Equations and Chemical Principles

• General Formula for Ionic Compounds:

$\text{Cation}^{+} + \text{Anion}^{-} \rightarrow \text{Ionic Compound}$

• General Formula for Covalent Compounds:

$\text{A} + \text{B} \rightarrow \text{A--B}$

• Hydrogen Bond Representation:

$\text{A--H} \cdots \text{B}$

Additional info: The course will also cover the structure and function of major organ systems, the movement of substances across membranes, and the integration of physiological processes.