The Chemistry of Life

Introduction

The study of Anatomy & Physiology requires a foundational understanding of chemistry, as all biological processes are governed by chemical principles. This section introduces the essential chemical concepts relevant to the human body.

Matter

Definition and States of Matter

• Matter: Anything that has mass and occupies space.

• Matter exists in three states: solid, liquid, and gas.

• Chemistry: The study of matter and its interactions.

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

Atoms and Atomic Structure

Subatomic Particles

• Atoms are composed of smaller structures called subatomic particles:

  • Protons (p+): Located in the atomic nucleus; positively charged.

  • Neutrons (n0): Located in the atomic nucleus; slightly larger than protons; no charge.

  • Electrons (e-): Found outside the atomic nucleus; negatively charged.

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

• The number of neutrons can vary without affecting the charge.

Electron Shells

• Electron shells are regions surrounding the atomic nucleus where electrons exist.

• Each shell can hold a specific number of electrons:

  • 1st shell (closest to nucleus): holds up to 2 electrons.

  • 2nd shell: holds up to 8 electrons.

Elements in the Periodic Table and the Human Body

Atomic Number and Elements

• The atomic number is the number of protons in an atom's nucleus and defines the element.

• Element: A substance that cannot be broken down into simpler substances by chemical means.

• All atoms of an element have the same number of protons.

Major Elements in the Human Body

• The human body is primarily composed of four major elements:

  • Hydrogen (H)

  • Oxygen (O)

  • Carbon (C)

  • Nitrogen (N)

• Additionally, there are 7 mineral elements and 13 trace elements essential for physiological functions.

Isotopes and Radioactivity

Mass Number and Isotopes

• Mass number: The sum of all protons and neutrons in the atomic nucleus.

• Isotope: Atoms of the same element (same number of protons) but different mass numbers (different number of neutrons).

• Examples of hydrogen isotopes:

  • 1H: Hydrogen

  • 2H: Deuterium

  • 3H: Tritium

Radioisotopes

• Radioisotopes: Unstable isotopes that release high energy or radiation through radioactive decay, allowing the isotope to become more stable.

• Radioisotopes have important medical applications, such as imaging and cancer therapy.

Example: Tritium (3H) is a radioactive isotope of hydrogen used in biological tracing.

Additional info: Understanding isotopes is crucial for interpreting diagnostic imaging and understanding metabolic processes in Anatomy & Physiology.