Basic Principles of Chemistry for Anatomy & Physiology

Basic Principles of Chemistry

Introduction

Chemistry is fundamental to understanding the structure and function of the human body. All physiological processes are underpinned by chemical principles, from cellular respiration to muscle contraction and neural signaling. This section introduces the essential chemical concepts relevant to Anatomy & Physiology.

Elements and Atoms

Elements

• Element: A substance that cannot be broken down into simpler substances by ordinary chemical means.

• There are 118 known elements, of which about 24 are found in the human body.

• Four elements—carbon (C), oxygen (O), hydrogen (H), and nitrogen (N)—make up approximately 96% of body mass.

• Other elements, such as calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, and iron, are present in smaller amounts but are essential for life.

Atoms

• Atom: The smallest unit of an element that retains the properties of that element.

• Atoms consist of a nucleus (protons and neutrons) and electrons orbiting the nucleus.

• The unique arrangement of protons, neutrons, and electrons gives each element its specific chemical and physical properties.

Molecules and Compounds

Definitions

• Molecule: A general term for two or more atoms bonded together (e.g., O2, H2O).

• Compound: A molecule that contains two or more different kinds of atoms chemically bonded together (e.g., C6H12O6).

• Example: Glucose (C6H12O6) is a compound because it contains more than one type of atom.

• Molecules composed of only one type of atom (e.g., O2, H2) are not considered compounds.

Mixtures

Types of Mixtures

• Mixture: Two or more substances physically intermixed, not chemically combined.

• Three basic types of mixtures in the body:

  • Solutions: Homogeneous mixtures with very small solute particles (e.g., mineral water).

  • Colloids (Emulsions): Heterogeneous mixtures with larger solute particles that do not settle out (e.g., Jell-O, cytosol of cells).

  • Suspensions: Heterogeneous mixtures with large, visible solute particles that settle out over time (e.g., blood, where blood cells settle if left standing).

Properties of Mixtures

• Mixtures can be separated by physical means (e.g., filtration, evaporation).

• Mixtures do not involve chemical bonding between components.

• Mixtures can be homogeneous (solutions) or heterogeneous (colloids and suspensions).

Comparison: Mixtures vs. Compounds

• Mixtures: No chemical bonding, components retain their original properties, can be separated physically.

• Compounds: Chemical bonds form between elements, properties differ from component elements, can only be separated by chemical means.

Table: Types of Mixtures

Type	Particle Size	Appearance	Example
Solution	Very small (molecular, < 1 nm)	Clear, does not scatter light	Mineral water, saline
Colloid	Intermediate (1–100 nm)	Cloudy, scatters light	Jell-O, cytosol
Suspension	Large (> 100 nm)	Cloudy, particles settle out	Blood (with cells)

Key Terms in Chemistry

• Solvent: The substance present in the greatest amount in a solution (usually a liquid, such as water).

• Solute: The substance dissolved in the solvent (e.g., glucose in blood plasma).

• Homogeneous mixture: A mixture with uniform composition throughout (e.g., solution).

• Heterogeneous mixture: A mixture with non-uniform composition (e.g., suspension, colloid).

Application to Body Processes

• Chemical principles underlie all physiological reactions, including movement, digestion, heart function, and nervous system activity.

• Understanding the nature of elements, atoms, molecules, compounds, and mixtures is essential for comprehending how the body functions at the molecular and cellular levels.

Additional info:

• Water is the most abundant solvent in the human body and is vital for dissolving and transporting substances.

• Electrolytes are compounds that dissociate into ions in solution and are crucial for nerve impulse transmission and muscle contraction.