Chapter 2: Chemistry Comes Alive

The Chemical Level of Organization

This chapter introduces the foundational chemical principles necessary for understanding physiological processes in the human body. It covers basic chemistry concepts, the nature of matter and energy, and the structure and function of atoms, molecules, and mixtures as they relate to anatomy and physiology.

Basic Chemistry: Matter, Work & Energy

Definitions and Properties

• Matter: Anything that occupies space and has mass. Examples include solids, liquids, and gases.

• Energy: The capacity to do work or put matter into motion. Energy exists in various forms and is essential for physiological processes.

Forms of Energy

• Kinetic Energy: Energy in action, such as movement of muscles or ions across membranes.

• Potential Energy: Stored energy, such as energy stored in chemical bonds (e.g., glucose, ATP).

Types of Energy Important in Physiology

• Chemical Energy: Energy stored in chemical bonds; released during chemical reactions.

• Electrical Energy: Results from movement of charged particles (e.g., nerve impulses).

• Mechanical Energy: Directly involved in moving matter (e.g., muscle contraction).

• Radiant/Electromagnetic Energy: Energy that travels in waves (e.g., light energy for vision).

Work and Energy Transfer

• Work is performed when energy is used to move an object or change the state of matter.

• Energy conversions are not 100% efficient; some energy is lost as heat.

Composition of Matter: Atoms & Elements

Atoms and Atomic Structure

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

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

• Atomic Number: Number of protons in the nucleus; defines the element.

• Mass Number: Sum of protons and neutrons in the nucleus.

Subatomic Particles

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

• Electrons: Negatively charged particles orbiting the nucleus.

Isotopes

• Isotopes: Atoms of the same element with different numbers of neutrons, resulting in different mass numbers.

• Some isotopes are radioactive and can be used in medical imaging and treatments.

Elements Essential for Life

• Major elements in the human body: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N)

• These elements make up over 96% of body mass.

• Other important elements: Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), Magnesium (Mg), and Iron (Fe).

Atomic Weight and Chemical Symbols

• Atomic Weight: Average of the mass numbers of all isotopes of an element.

• Chemical Symbols: One- or two-letter abbreviations for elements (e.g., H for hydrogen, Na for sodium).

Combining Matter: Molecules & Mixtures

Molecules and Compounds

• Molecule: Two or more atoms bonded together (e.g., H2, O2).

• Compound: Molecule containing two or more different elements (e.g., H2O, NaCl).

Mixtures

• Mixture: Two or more components physically intermixed (not chemically bonded).

• Types of mixtures include solutions, colloids, and suspensions.

Solution Properties

• Solvent: Substance present in greatest amount (usually water in biological systems).

• Solute: Substance dissolved in the solvent.

• Concentration: Expressed as percent, milligrams per deciliter (mg/dL), or molarity (moles per liter).

Molecular Weight

• Molecular Weight: Sum of the atomic weights of all atoms in a molecule.

Table: Major Elements in the Human Body

Key Equations

• Atomic Number:

• Mass Number:

• Molecular Weight:

Summary & Applications

• Understanding chemistry is essential for studying physiology because all body functions depend on chemical interactions.

• Knowledge of atoms, elements, and molecules provides the basis for understanding cellular structure and function.

• Energy transformations underlie all physiological processes, from muscle contraction to nerve signaling.

Additional info: Some explanations and table entries were expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.