Basic Principles of Chemistry for Anatomy & Physiology

Basic Principles of Chemistry in Anatomy & Physiology

Introduction

Chemistry forms the foundation for understanding physiological processes in the human body. A basic knowledge of chemical principles is essential for studying anatomy and physiology, as all body functions depend on chemical interactions at the molecular and cellular levels.

Key Terms and Concepts in Basic Chemistry

Elements and Atoms

• Element: A pure substance that cannot be broken down into simpler substances by ordinary chemical methods. Examples include carbon, oxygen, hydrogen, and nitrogen.

• Atoms: The smallest units of an element that retain the properties of that element. Atoms are the building blocks for each element.

• Body Composition:

  • 4 elements (C, H, O, N) make up about 96% of the human body.

  • 9 elements make up about 3.9% of the body.

  • 11 elements make up less than 0.01% of the body.

Molecules and Compounds

• Molecule: A general term for two or more atoms bonded together (e.g., O2).

• Compound: A specific molecule that contains two or more different kinds of atoms bonded together (e.g., C6H12O6).

• Example: Water (H2O) is a compound, while oxygen gas (O2) is a molecule but not a compound.

Mixtures

Mixtures are physical combinations of two or more substances. They can be classified as:

• Solutions: Homogeneous mixtures where solute particles are very small and evenly distributed. Example: mineral water.

• Colloids: Heterogeneous mixtures with larger solute particles that do not settle out. Example: Jell-O.

• Suspensions: Heterogeneous mixtures with large, visible solute particles that tend to settle out. Example: a mixture of water and sand, or blood (where blood cells settle if left standing).

Comparison of Mixtures and Compounds

• Mixtures do not involve chemical bonding between components; compounds do.

• Mixtures can be separated by physical means; compounds require chemical means for separation.

• Mixtures can be homogeneous or heterogeneous; compounds are always homogeneous.

Types of Chemistry in the Body

Inorganic Chemistry

• Inorganic Compounds: Generally do not contain carbon (exceptions: CO2 and CO).

• Examples include water, salts, acids, and bases.

• Salts: Ionic compounds that dissociate in water to form ions. Important for nerve impulse transmission and muscle contraction (e.g., Na+, K+, Ca2+).

• Acids and Bases: Acids release hydrogen ions (H+), while bases accept hydrogen ions or release hydroxide ions (OH-).

pH Scale

• Measures the concentration of hydrogen ions in a solution.

• Scale ranges from 0 (most acidic) to 14 (most basic), with 7 being neutral.

• Body fluids are tightly regulated around pH 7.4; deviations can disrupt cellular function.

Organic Chemistry

• Organic Compounds: Always contain carbon and are usually large, covalently bonded molecules.

• Major classes include carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• Include sugars and starches; main function is to provide energy.

• Classified as monosaccharides (one sugar), disaccharides (two sugars), or polysaccharides (many sugars).

• Examples: glucose, fructose, galactose (monosaccharides); sucrose, lactose (disaccharides); glycogen, starch (polysaccharides).

• Some carbohydrates serve structural roles (e.g., ribose in RNA, deoxyribose in DNA).

Lipids

• Include triglycerides (fats and oils), phospholipids, steroids, and eicosanoids.

• Triglycerides: Major form of stored energy in the body.

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Include cholesterol, which is essential for cell membrane structure and as a precursor for steroid hormones (e.g., sex hormones, corticosteroids).

• Eicosanoids: Involved in inflammation and other body processes (e.g., prostaglandins).

Proteins

• Composed of amino acids; contain carbon, hydrogen, oxygen, and nitrogen.

• Functions include structural support, transport, movement, and catalysis (enzymes).

• Enzymes are proteins that speed up chemical reactions in the body.

Nucleic Acids

• Include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

• DNA stores genetic information and directs protein synthesis.

• RNA is involved in protein synthesis and gene regulation.

Summary Table: Types of Mixtures

Type	Particle Size	Appearance	Example	Settling?
Solution	Very small (molecular)	Clear, homogeneous	Mineral water	No
Colloid	Intermediate	Cloudy, homogeneous	Jell-O	No
Suspension	Large, visible	Cloudy, heterogeneous	Blood (cells in plasma)	Yes

Key Chemical Reactions in the Body

• Synthesis Reactions: Atoms or molecules combine to form larger, more complex molecules. Example: formation of proteins from amino acids.

• Decomposition Reactions: Molecules are broken down into smaller molecules or atoms. Example: breakdown of glycogen to glucose.

• Exchange Reactions: Involve both synthesis and decomposition; bonds are both made and broken.

Factors Affecting Chemical Reactions

• Temperature: Higher temperature increases reaction rate.

• Concentration: Higher concentration of reactants increases reaction rate.

• Particle Size: Smaller particles increase reaction rate.

• Catalysts: Substances that increase the rate of a reaction without being consumed (e.g., enzymes).

Acid-Base Balance and Homeostasis

• Body enzymes function within a narrow pH range; deviations can impair cell function and damage tissues.

• Acid-base balance is regulated by the kidneys, lungs, and chemical buffers.

• Buffers: Compounds that resist abrupt changes in pH by releasing or binding hydrogen ions as needed.

Conclusion

Understanding the basic principles of chemistry is essential for comprehending the structure and function of the human body. These principles underlie all physiological processes, from muscle contraction to genetic inheritance.