Basic Chemistry

Introduction

Chemistry is fundamental to understanding the structure and function of the human body. This chapter introduces the essential chemical principles that underpin anatomy and physiology, focusing on matter, energy, atomic structure, chemical bonds, and the major classes of biological molecules.

Matter and Energy

Definitions and Differences

• Matter: Anything that occupies space and has mass. All substances in the body are forms of matter.

• Energy: The capacity to do work or cause change. Energy does not have mass or occupy space.

Major Forms of Energy in the Body

• Chemical Energy: Stored in the bonds of chemical substances. Example: ATP provides energy for cellular processes.

• Electrical Energy: Results from movement of charged particles. Example: Nerve impulses are electrical signals.

• Mechanical Energy: Directly involved in moving matter. Example: Muscle contraction moves body parts.

Elements and Atoms

Elements

• Element: A pure substance composed of only one type of atom. Cannot be broken down by ordinary chemical means.

• Major Elements in the Body: Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N) form about 96% of body mass.

Atoms and Subatomic Particles

• Atom: The smallest unit of an element that retains its properties.

• Subatomic Particles:

  • Protons: Positive charge (+), located in the nucleus.

  • Neutrons: No charge (neutral), located in the nucleus.

  • Electrons: Negative charge (−), orbit the nucleus in electron shells.

Chemical Bonds and Reactions

Chemical Bonds

• Chemical Reaction: Involves the making or breaking of bonds between atoms through the interaction of electrons.

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating ions (charged particles).

• Covalent Bonds: Formed when atoms share electrons.

  • Polar Covalent Bonds: Unequal sharing of electrons, resulting in partial charges (e.g., water).

  • Nonpolar Covalent Bonds: Equal sharing of electrons (e.g., oxygen gas).

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (important in water and DNA structure).

Types of Chemical Reactions

• Synthesis Reaction: Atoms or molecules combine to form a larger, more complex molecule. Example:

• Decomposition Reaction: A molecule is broken down into smaller molecules or atoms. Example:

Molecules, Compounds, and Mixtures

Definitions

• Molecule: Two or more atoms held together by chemical bonds (e.g., O2).

• Compound: A molecule containing two or more different elements (e.g., H2O).

Inorganic and Organic Compounds

Distinguishing Features

• Inorganic Compounds: Usually lack carbon; include water, salts, acids, and bases.

• Organic Compounds: Contain carbon; include carbohydrates, lipids, proteins, and nucleic acids.

Water and Homeostasis

• Water: Most abundant inorganic compound in the body; vital for temperature regulation, chemical reactions, and transport of substances.

Salts, Acids, and Bases

• Salt: Ionic compound that dissociates into ions in water.

• Acid: Releases hydrogen ions (H+) in solution.

• Base: Releases hydroxide ions (OH−) or accepts H+ in solution.

pH Concept

• pH: Measures the concentration of hydrogen ions in a solution. Scale ranges from 0 (acidic) to 14 (basic).

• Blood pH: Normally maintained between 7.35 and 7.45.

Organic Molecules: Synthesis and Breakdown

Dehydration Synthesis and Hydrolysis

• Dehydration Synthesis: Joins monomers by removing water to form polymers.

• Hydrolysis: Breaks polymers into monomers by adding water.

Carbohydrates and Lipids

Comparison

• Carbohydrates: Composed of monosaccharides (simple sugars); primary energy source for cells.

• Lipids: Composed of fatty acids and glycerol; function in energy storage, insulation, and cell membranes.

Nucleic Acids: DNA and RNA

Structures and Functions

• DNA (Deoxyribonucleic Acid): Double-stranded helix; stores genetic information.

• RNA (Ribonucleic Acid): Single-stranded; involved in protein synthesis.

ATP: The Energy Currency

Importance of ATP

• ATP (Adenosine Triphosphate): Main energy carrier in cells; provides energy for cellular work.