Chapter 2: Chemistry Foundations for Anatomy & Physiology

Chemistry and Matter in Anatomy & Physiology

Introduction to Matter and Chemistry

Chemistry is fundamental to understanding the structure and function of the human body. Matter is anything that has mass and occupies space, and it exists in three states: solid, liquid, and gas. Chemistry is the study of matter and its interactions, which underpins all biological processes.

• Matter: Anything that has mass and occupies space; can be solid, liquid, or gas.

• Chemistry: The scientific study of matter, its properties, and how it interacts and changes.

Atoms and Atomic Structure

Atoms: The Building Blocks of Matter

An atom is the smallest unit of matter that retains the properties of an element. Atoms are composed of even smaller structures called subatomic particles.

• Protons (p+): Positively charged particles located in the atomic nucleus.

• Neutrons (n0): Neutral particles, slightly larger than protons, also in the nucleus.

• Electrons (e-): Negatively charged particles found outside the nucleus in electron shells.

• Atoms are electrically neutral when the number of protons equals the number of electrons.

Example: A carbon atom has 6 protons, 6 neutrons, and 6 electrons.

Electron Shells and Valence Electrons

Electrons occupy regions called electron shells around the nucleus. Each shell can hold a specific number of electrons:

• 1st shell: 2 electrons

• 2nd shell: 8 electrons

• 3rd shell: 18 electrons (satisfied with 8 for most biological atoms)

Valence electrons are those in the outermost shell and are crucial for chemical bonding.

Elements and the Periodic Table

Atomic Number and Elements

The atomic number is the number of protons in the nucleus and defines each element. An element is a substance that cannot be broken down into simpler substances by chemical means. Each element is made of atoms with the same number of protons.

The Periodic Table: Organization and Symbols

The periodic table lists elements by increasing atomic number and groups them by shared properties. Each element is represented by a chemical symbol.

• Groups: Columns of elements with similar chemical properties.

• Major elements: Make up 96% of the human body (e.g., C, H, O, N).

• Mineral elements: Make up less than 4% (e.g., Na, K, Ca, Mg).

• Trace elements: Present in very small amounts (e.g., Fe, I, Zn).

Elements in the Human Body

The human body is primarily composed of four major elements, with additional mineral and trace elements essential for physiological functions.

Element Type	Examples	Body Percentage
Major Elements	Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N)	~96%
Mineral Elements	Sodium (Na), Potassium (K), Calcium (Ca), Magnesium (Mg)	<4%
Trace Elements	Iron (Fe), Iodine (I), Zinc (Zn), Selenium (Se)	0.01%

Key Terms and Concepts

• Atom: Smallest unit of an element retaining its properties.

• Element: Pure substance made of only one kind of atom.

• Atomic Number: Number of protons in an atom's nucleus.

• Electron Shell: Region around nucleus where electrons are found.

• Valence Electrons: Electrons in the outermost shell, important for bonding.

• Periodic Table: Chart organizing elements by atomic number and properties.

• Chemical Symbol: Abbreviation for an element (e.g., H for hydrogen).

Applications in Anatomy & Physiology

• Understanding atomic structure and elements is essential for grasping how molecules form and interact in the body.

• Major, mineral, and trace elements play critical roles in physiological processes such as oxygen transport, nerve signaling, and enzyme function.

Additional info: The periodic table is a foundational tool for understanding the chemical basis of life, including the composition of body tissues and fluids, and the mechanisms of metabolism and cellular function.