Chemistry Foundations
This article is part 0 of a Anatomy & Physiology Series for healthcare professionals
Life begins with chemistry. Every cell in your body is built from atoms. These atoms combine to form molecules, which in turn build the larger structures that make up cells, tissues, organs, organ systems, and ultimately the human body. In many ways, chemistry is the foundation of anatomy and physiology. Before we can understand how muscles contract, nerves transmit signals, or organs work together, we must first understand the chemical building blocks of life. Understanding these foundations will make the rest of anatomy and physiology much easier to understand.
From Atoms to the Human Body
Matter, Elements and Atom
Everything around us is made of matter. Matter is anything that has mass and occupies space. Your bones, muscles, blood, skin, and even the air you breathe are all forms of matter. Matter is composed of elements, which are pure substances consisting of only one type of atom. Although over one hundred elements exist in nature, only a small number are responsible for building the human body. The six most important elements are:
| Element | Symbol | Primary Role |
|---|---|---|
| Carbon | C |
Forms the backbone of organic molecules, including carbohydrates, proteins, lipids, and nucleic acids.
Carbon is essential because it can form four strong covalent bonds , allowing it to create stable chains and complex structures that make up biological molecules. |
| Hydrogen | H | A major component of water and organic molecules. It also plays an important role in maintaining the body's acid–base (pH) balance through hydrogen ions (H⁺) |
| Oxygen | O | Essential for cellular respiration, the process that produces energy (ATP), and is a major component of water. |
| Nitrogen | N | Required for the formation of amino acids, proteins, DNA, and RNA. |
| Phosphorus | P | A key component of ATP, DNA, RNA, phospholipid cell membranes, and bones. |
| Sulfur | S | Found in certain amino acids and proteins, where it helps stabilize protein structure. |
The Structure of an Atom
Every atom consists of three basic particles. The nucleus forms the dense center of the atom and contains protons and neutrons. Electrons move around the nucleus in regions called the electron cloud. Atoms rarely exist alone. Instead, they combine with one another by forming chemical bonds. When two or more atoms bond together, they form a molecule. Will talk more about molecule in next section
| Particle | Charge | Location |
|---|---|---|
| Proton | Positive (+) | Nucleus |
| Neutron | Neutral (0) | Nucleus |
| Electron | Negative (−) | Electron cloud |
Molecules and Macromolecules
When two or more atoms bond together, they form a molecule. Examples include:
Water (H₂O)
Oxygen (O₂)
Carbon dioxide (CO₂)
Glucose (C₆H₁₂O₆)
Some molecules are relatively simple, while others contain thousands of atoms. Large biological molecules are called macromolecules. These molecules perform nearly every important function inside living organisms.
Examples include:
Proteins
DNA
RNA
Glycogen
Cell membrane phospholipids
These macromolecules combine to form cells, which become tissues, organs, organ systems, and ultimately the human body.
Electrolytes
When certain substances dissolve in water, they separate into charged particles called ions. These ions are known as electrolytes.
Common electrolytes include:
Sodium (Na⁺)
Potassium (K⁺)
Calcium (Ca²⁺)
Chloride (Cl⁻)
Electrolytes are essential for:
nerve impulses
muscle contraction
maintaining fluid balance
regulating pH
