Basic Chemistry for Anatomy & Physiology

Matter and Energy

Understanding matter and energy is fundamental to the study of anatomy and physiology, as all biological processes depend on chemical interactions.

• Matter: Anything that occupies space and has mass. Exists in three states:

  • Solid: Definite shape and volume

  • Liquid: Definite volume, takes shape of container

  • Gas: Neither definite shape nor volume

• Physical changes: Do not alter the basic nature of a substance (e.g., change of state)

• Chemical changes: Alter the chemical composition of a substance

• Energy: The ability to do work; has no mass and does not take up space

  • Kinetic energy: Energy in action

  • Potential energy: Stored energy

• Forms of energy:

  • Chemical energy: Stored in chemical bonds

  • Electrical energy: Movement of charged particles

  • Mechanical energy: Directly involved in moving matter

  • Radiant energy: Travels in waves (electromagnetic spectrum)

• ATP (Adenosine Triphosphate): Traps chemical energy of food in its bonds for cellular use

Composition of Matter

All living things are composed of elements and atoms, which are the building blocks of matter.

• Elements: Fundamental units of matter; 96% of the human body is made from four elements:

  • Oxygen (O): 65% of body mass

  • Carbon (C)

  • Hydrogen (H)

  • Nitrogen (N)

• Atoms: Smallest units of elements; differ from one another; represented by atomic symbols

Common Elements in the Human Body

Atomic Structure

Atoms consist of subatomic particles: protons, neutrons, and electrons.

• Protons (p+): Positively charged, located in nucleus

• Neutrons (n0): Neutral, located in nucleus

• Electrons (e-): Negatively charged, orbit nucleus

• Atoms are electrically neutral: number of protons equals number of electrons

• Ions: Atoms that have lost or gained electrons

Subatomic Particles Table

Identifying Elements

Each element is identified by its atomic number, mass number, and atomic weight.

• Atomic number: Number of protons

• Atomic mass number: Sum of protons and neutrons

• Atomic weight: Approximate mass of the most abundant isotope

Isotopes and Radioactivity

Isotopes are atoms of the same element with different numbers of neutrons. Some isotopes are radioactive and used in medical tracing.

• Isotopes: Same atomic number, different atomic mass

• Radioisotopes: Unstable, decompose to stable forms, emit radioactivity

Molecules and Compounds

Molecules are formed when atoms combine chemically. Compounds are molecules made of different elements.

• Molecule: Two or more atoms of the same element

• Compound: Two or more atoms of different elements

• Example: (water)

Chemical Bonds and Reactions

Chemical bonds are energy relationships involving electrons. Chemical reactions occur when atoms combine or dissociate.

• Electron shells: Energy levels where electrons reside

• Shell 1: 2 electrons; Shell 2: 8 electrons; Shell 3: 18 electrons

• Valence shell: Outermost shell; bonding occurs here

• Rule of eights: Atoms are stable with 8 electrons in valence shell (except shell 1)

Types of Chemical Bonds

• Ionic bonds: Electrons are transferred; forms ions (anions and cations)

• Covalent bonds: Electrons are shared; can be single or double bonds

• Nonpolar covalent: Electrons shared equally

• Polar covalent: Electrons shared unequally; molecule has poles

• Hydrogen bonds: Weak bonds; important in water and protein structure

Patterns of Chemical Reactions

Chemical reactions in the body follow specific patterns.

• Synthesis reaction: Atoms/molecules combine to form larger molecules; energy absorbed (anabolic)

• Decomposition reaction: Molecule broken down; energy released (catabolic)

• Exchange reaction: Bonds are made and broken; parts switch

• Most reactions are reversible; indicated by double arrows

Factors Increasing Rate of Chemical Reactions

Biochemistry: Chemical Composition of Living Matter

Biochemistry distinguishes between inorganic and organic compounds.

• Inorganic compounds: Lack carbon; small, simple molecules (water, salts, acids, bases)

• Organic compounds: Contain carbon; large, covalent molecules (carbohydrates, lipids, proteins, nucleic acids)

Inorganic Compounds

• Water: Most abundant; high heat capacity, polarity, chemical reactivity, cushioning

• Salts: Ionic compounds; dissociate in water; vital for nerve impulses

• Acids: Release H+ ions; proton donors

• Bases: Release OH- ions; proton acceptors

• Neutralization: Acids and bases react to form water and salt

• pH: Measures H+ concentration; scale 0–14; buffers regulate pH

Organic Compounds

• Polymers: Chains of monomers; formed by dehydration synthesis, broken by hydrolysis

• Carbohydrates: Contain C, H, O; sugars and starches; classified as monosaccharides, disaccharides, polysaccharides

• Lipids: Triglycerides, phospholipids, steroids; insoluble in water

• Proteins: Construction materials, enzymes, hormones, antibodies; built from amino acids

• Nucleic acids: DNA and RNA; built from nucleotides; store and transmit genetic information

• ATP: Energy currency of cells; composed of ribose, adenine, and three phosphate groups

Representative Lipids Table

Representative Functional Proteins Table

Summary

This chapter provides foundational knowledge of chemistry as it applies to human anatomy and physiology, including the structure and function of atoms, elements, molecules, and compounds, as well as the importance of chemical reactions and biological molecules in the human body.