Basic Chemistry for Anatomy & Physiology

Basic Chemistry for Anatomy & Physiology

Introduction

Chemistry forms the foundation for understanding the structure and function of the human body. This section introduces the essential chemical principles relevant to anatomy and physiology, including the nature of matter and energy, the elements that compose the human body, and the basic forms of energy used in biological processes.

Matter and Its States

Definition and Properties of Matter

• Matter is anything that occupies space and has mass.

• Matter exists in three primary states:

  • Solid: Definite shape and volume (e.g., bones, teeth).

  • Liquid: Definite volume, takes the shape of its container (e.g., blood, plasma).

  • Gas: Neither definite shape nor volume (e.g., oxygen, carbon dioxide in the lungs).

Energy in Biological Systems

Definition and Types of Energy

• Energy is the ability to do work or cause change.

• Two main forms of energy:

  • Kinetic energy: Energy in action (e.g., muscle contraction).

  • Potential energy: Stored energy (e.g., energy stored in chemical bonds).

Forms of Energy in the Body

• Chemical energy: Stored in the bonds of chemical substances; released during chemical reactions (e.g., breakdown of glucose).

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

• Mechanical energy: Directly involved in moving matter (e.g., muscle movement).

• Radiant energy: Travels in waves; includes energy of the electromagnetic spectrum (e.g., light energy for vision).

Elements of the Human Body

Major Elements

The human body is composed primarily of a few key elements, each with specific roles in physiological processes.

Element	Atomic Symbol	Percentage of Body Mass	Role
Oxygen	O	65.0%	Major component of both organic and inorganic molecules; essential for oxidation of glucose and other fuels to produce ATP (cellular energy).
Carbon	C	18.5%	Primary element in all organic molecules, including carbohydrates, lipids, proteins, and nucleic acids.
Hydrogen	H	9.5%	Component of most organic molecules; as an ion (proton), it influences the pH of body fluids.
Nitrogen	N	3.2%	Component of proteins and nucleic acids (genetic material).

Minor Elements

Element	Atomic Symbol	Percentage of Body Mass	Role
Calcium	Ca	1.5%	Found as a salt in bones and teeth; in ionic form, required for muscle contraction, neural transmission, and blood clotting.
Phosphorus	P	1.0%	Present as a salt, in combination with calcium, in bones and teeth; present in nucleic acids and many proteins; forms part of ATP (energy compound).
Potassium	K	0.4%	In ionic form, the major intracellular cation; necessary for conduction of nerve impulses and muscle contraction.
Sulfur	S	0.3%	Component of proteins, particularly contractile proteins of muscle.

Additional info: Other trace elements (such as sodium, chlorine, magnesium, iron, iodine, etc.) are also essential for various physiological functions, including fluid balance, oxygen transport, and hormone production.

Summary

• Understanding the basic chemical composition and energy forms in the body is essential for studying anatomy and physiology.

• The four most abundant elements—oxygen, carbon, hydrogen, and nitrogen—make up over 96% of body mass and are critical for life processes.

• Energy in various forms powers all physiological activities, from muscle contraction to nerve signaling.