Chemistry Fundamentals for Anatomy & Physiology I

Chemistry Basics for Anatomy & Physiology

Introduction to Chemistry in Biological Systems

Chemistry is foundational to understanding anatomy and physiology, as all biological processes are governed by chemical principles. This section introduces the essential chemical concepts relevant to the human body.

Basics of Chemistry

Definition of Matter

• Matter: Anything that has mass and takes up space. Matter exists in three states: solid, liquid, and gas.

• Example: Water (H2O) can exist as ice (solid), liquid water, or steam (gas).

Mass

• Mass: The quantity of material in matter. On Earth, mass is often measured as weight, but mass remains constant regardless of location.

Atoms: The Building Blocks of Matter

Structure of Atoms

• Atom: The smallest unit of matter; the fundamental building block of all substances.

• Atoms are composed of three subatomic particles:

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

  • Neutrons (n0): Neutral (uncharged) particles also found in the nucleus.

  • Electrons (e-): Negatively charged particles that orbit the nucleus in an electron cloud.

Atomic Number and Mass Number

• Atomic Number: The number of protons in an atom, which defines the element.

• Mass Number: The total number of protons and neutrons in an atom.

• Element: A substance composed only of atoms with the same atomic number (e.g., hydrogen).

Principal Elements in the Human Body

The human body is primarily composed of four elements, which together account for 96.5% of total body weight:

Element	Symbol	% of Total Body Weight	Significance
Oxygen	O	65	Component of water and other compounds; essential for respiration
Carbon	C	18.6	Found in all organic molecules
Hydrogen	H	9.7	Component of water and most other compounds in the body
Nitrogen	N	3.2	Found in proteins, nucleic acids, and other organic compounds

Hydrogen Atom Example

• Hydrogen (H): The simplest atom, with an atomic number of 1.

• Consists of 1 proton and 1 electron (no neutrons in the most common isotope).

• The electron orbits the nucleus in an electron cloud.

Isotopes and Atomic Mass

• Isotopes: Atoms of the same element with the same number of protons but different numbers of neutrons.

• Atomic Mass: The average mass of an atom of a specific element, measured in daltons.

• Example: Hydrogen-1 (protium) has 1 proton; Hydrogen-2 (deuterium) has 1 proton and 1 neutron.

Electron Shells

• Electrons occupy energy levels called shells around the nucleus.

• The first shell can hold up to 2 electrons; the second and third shells can each hold up to 8 electrons.

• Atoms are most stable when their outermost shell is full.

Summary Table: Atomic Structure

Subatomic Particle	Charge	Location
Proton	+1	Nucleus
Neutron	0	Nucleus
Electron	-1	Electron cloud (shells)

Additional info: Later sections would cover chemical bonding, ions, and the role of these elements in physiological processes.