Chapter 2: The Chemical Level of Organization – Fundamentals of Anatomy & Physiology

The Chemical Level of Organization

Introduction

The chemical level of organization forms the foundation for understanding anatomy and physiology. Chemistry explains the structure of matter, including atoms, molecules, and compounds, and how these building blocks interact to support life processes.

Atoms and Atomic Structure

Matter and Atoms

• Matter is anything that takes up space and has mass.

• All matter is composed of atoms, which join together to form chemicals with distinct characteristics.

• Chemical characteristics of atoms determine physiological functions at molecular and cellular levels.

Subatomic Particles

• Protons: Positively charged, 1 mass unit.

• Neutrons: Neutral charge, 1 mass unit.

• Electrons: Negatively charged, very low mass.

Atomic Structure

• Atomic number: Number of protons in the nucleus; determines the element's identity.

• Nucleus: Central region containing protons and neutrons.

• Electron cloud: Spherical area surrounding the nucleus where electrons are found.

• Electron shell: A two-dimensional representation of the electron cloud, showing energy levels.

Example: Atom Diagram

The nucleus is at the center of the atom, surrounded by the electron cloud where electrons are likely to be found.

Principal Elements in the Human Body

Overview

The human body is composed of several principal elements, each with specific physiological roles.

Element	(% of total body weight)	Significance
Oxygen (O)	65.0	A component of water and other compounds; gaseous form is essential for respiration.
Carbon (C)	18.6	Found in all organic molecules.
Hydrogen (H)	9.7	A component of water and most other compounds in the body.
Nitrogen (N)	3.2	Found in proteins, nucleic acids, and other organic compounds.
Calcium (Ca)	1.8	Found in bones and teeth; important for membrane function, nerve impulses, muscle contraction, and blood clotting.
Phosphorus (P)	1.0	Found in bones and teeth, nucleic acids, and high-energy compounds.
Potassium (K)	0.4	Important for proper membrane function, nerve impulses, and muscle contraction.

Learning Outcomes for the Chemical Level

Key Concepts

• Describe an atom and how atomic structure affects interactions between atoms.

• Compare the ways in which atoms combine to form molecules and compounds.

• Distinguish among the major types of chemical reactions important for physiology.

• Describe the crucial role of enzymes in metabolism.

• Distinguish between inorganic and organic compounds.

• Explain how the chemical properties of water make life possible.

• Explain what pH is and discuss its importance.

• Describe the physiological roles of acids, bases, and buffers in body fluids.

• Describe monomers and polymers, and the importance of functional groups in organic compounds.

• Discuss the structures and functions of carbohydrates, lipids, proteins, nucleic acids, and high-energy compounds.

Chemistry in Anatomy & Physiology

Importance

• Chemistry is the science that deals with the structure of matter.

• Understanding the structure of atoms and how they combine is essential for grasping physiological processes.

• Basic chemical building blocks form increasingly complex structures, supporting life at the cellular and molecular levels.

Summary Table: Principal Elements in the Human Body

This table summarizes the most abundant elements in the human body and their physiological significance.

Element	Body Weight (%)	Physiological Role
Oxygen	65.0	Essential for respiration and water formation.
Carbon	18.6	Backbone of organic molecules.
Hydrogen	9.7	Component of water and organic compounds.
Nitrogen	3.2	Found in proteins and nucleic acids.
Calcium	1.8	Bone structure, muscle contraction, nerve function.
Phosphorus	1.0	Bone structure, nucleic acids, energy compounds.
Potassium	0.4	Membrane function, nerve impulses, muscle contraction.

Conclusion

Understanding the chemical level of organization is essential for studying anatomy and physiology. Atoms, elements, and their interactions form the basis for all biological structures and processes, influencing everything from cellular function to the physiology of the entire organism.