Chemical Level of Organization: Foundations for Anatomy & Physiology

Chemical Level of Organization

Introduction

The chemical level of organization is the foundation of anatomy and physiology, focusing on the elements, compounds, and reactions that make up living matter. Understanding these basics is essential for grasping how the human body functions at higher levels of organization.

Major Classes of Chemical Compounds

Inorganic Compounds

• Water: The most abundant inorganic compound in living systems, vital for life.

• Salts: Ionic compounds that dissociate in water to form ions.

• Acids & Bases: Substances that affect hydrogen ion concentration in solutions.

Organic Compounds

• Carbohydrates: Energy sources and structural components.

• Lipids: Energy storage, cell membrane structure.

• Proteins: Structural, functional, and regulatory roles.

• Nucleic Acids: Genetic information storage and transfer.

Elements in the Human Body

Most Abundant Elements

Four elements make up about 96% of body weight:

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

These elements are essential for forming the molecules that constitute living tissues.

Biochemistry: The Study of Chemical Composition

Definition

• Biochemistry is the study of the chemical composition and reactions of living matter.

• All chemicals in the body are classified as either organic or inorganic compounds.

Ions in the Body

Cations and Anions

Ions are charged particles formed when atoms gain or lose electrons. They play critical roles in physiological processes.

Cations	Symbol	Anions	Symbol
Hydrogen ion	H+	Fluoride ion	F-
Sodium ion	Na+	Chloride ion	Cl-
Potassium ion	K+	Iodide ion	I-
Ammonium ion	NH4+	Hydroxide ion	OH-
Hydronium ion	H3O+	Nitrate ion	NO3-
Magnesium ion	Mg2+	Bicarbonate ion	HCO3-
Calcium ion	Ca2+	Oxide ion	O2-
Iron (II) ion	Fe2+	Sulfate ion	SO42-
Iron (III) ion	Fe3+	Phosphate ion	PO43-

Properties of Water

Importance and Functions

• Water is the most important and abundant inorganic compound in living systems.

• It acts as a solvent, dissolving many substances (universal solvent).

• Dissolved materials are called solutes.

• Solvent plus solutes make up a solution (e.g., saline solution: 0.9% NaCl in water).

Acids, Bases, and Salts

Definitions and Examples

• Acids: Compounds that dissociate in water to release hydrogen ions (H+).

• Bases: Compounds that dissociate to release hydroxide ions (OH-), or accept H+ ions.

• Salts: Ionic compounds that dissociate into cations and anions, neither of which is H+ or OH- (e.g., NaCl, CaCO3).

Acids, bases, and salts are essential for maintaining physiological pH and ionic balance.

pH Scale

Measurement and Significance

• pH is a measure of hydrogen ion concentration in a solution.

• pH ranges from 0 to 14; each unit represents a tenfold change in H+ concentration.

• Neutral pH is 7: $[H^+] = [OH^-]$

• Below pH 7: acidic (more H+ ions)

• Above pH 7: basic (more OH- ions)

Acid-Base Balance

Homeostasis and Regulation

• Normal blood pH: 7.35–7.45 (narrow range)

• Deviations can be fatal; maintaining pH is crucial for homeostasis.

• Three homeostatic mechanisms regulate acid-base balance:

  1. Buffer systems

  2. Respiratory regulation

  3. Renal (kidney) regulation

• Buffers resist abrupt changes in pH by releasing or binding hydrogen ions.

Organic Compounds

General Characteristics

• Organic molecules contain carbon and are often large.

• Carbon atoms can form chains and rings, making diverse structures.

• Monomers join to form macromolecules (polymers).

• Four major classes: Carbohydrates, Lipids, Proteins, Nucleic Acids.

Carbohydrates

Structure and Functions

• General formula: $[CH_2O]_n$ (n = number of carbon atoms)

• Example: Glucose ($C_6H_{12}O_6$)

• Functions:

  1. Broken down for chemical energy (ATP production)

  2. Stored as glycogen for future energy needs

  3. Structural components of DNA, RNA, cells, and tissues

Types of Carbohydrates:

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

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

• Polysaccharides: Many monosaccharides joined (e.g., glycogen)

Example: Glycogen is the storage form of glucose in animals; starch is the storage form in plants.

Summary Table: Major Macromolecules

Macromolecule	Building Blocks	Main Functions
Carbohydrates	Monosaccharides	Energy, structure
Lipids	Fatty acids, glycerol	Energy storage, membranes
Proteins	Amino acids	Structure, enzymes, regulation
Nucleic Acids	Nucleotides	Genetic information

Additional info:

• Further details on lipids, proteins, and nucleic acids are covered in subsequent sections of the course.

• Understanding chemical properties is essential for topics such as metabolism, cellular function, and physiological regulation.