BackUnit 2: The Chemistry of Life – Essential Elements, Water, and pH in Anatomy & Physiology
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Major Elements Found in the Body
Overview of Elements in Human Biology
The human body is composed of a variety of chemical elements, each playing a crucial role in physiological processes. These elements are classified based on their abundance and function.
Major elements (96%): Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N) are the most abundant and essential for life.
Mineral elements (<4%): Elements such as Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), and Magnesium (Mg) are required in smaller amounts for various physiological functions.
Trace elements (0.01%): Elements like Iron (Fe), Copper (Cu), Zinc (Zn), Iodine (I), and Selenium (Se) are needed in minute quantities but are vital for enzyme function and other processes.
Example: Calcium is essential for bone structure and muscle contraction, while iron is necessary for oxygen transport in hemoglobin.
Life Depends on Water
Properties of Water
Water is fundamental to life due to its unique physical and chemical properties, which support biological processes.
Solubility: Water dissolves a wide range of substances, making it an excellent solvent for biochemical reactions.
High heat capacity: Water can absorb and retain heat, helping to stabilize body temperature.
High heat of vaporization: Water requires significant energy to change from liquid to gas, aiding in cooling mechanisms like sweating.
Reactivity: Water participates in many chemical reactions, including hydrolysis and dehydration synthesis.
Cohesion/Adhesion: Water molecules stick to each other (cohesion) and to other surfaces (adhesion), facilitating transport in biological systems.
Example: Blood is approximately 90% water, serving as a transport medium for nutrients, gases, and waste products.
Additional info: About 60% of body weight is water, distributed in intracellular and extracellular spaces.
Water Is the Biological Solvent
Solvent and Solute Definitions
Water acts as the universal solvent in biological systems, allowing for the dissolution and transport of various substances.
Solvent: The liquid in which substances dissolve (water in biological systems).
Solute: Any dissolved substance (e.g., salts, sugars).
Hydrophilic: Polar molecules that interact easily with water (e.g., glucose, ions).
Hydrophobic: Nonpolar molecules that do not interact or dissolve in water (e.g., lipids).
Example: Table salt (NaCl) dissolves in water as Na+ and Cl- ions, while oil does not mix due to its hydrophobic nature.
The Importance of Hydrogen Ions and pH
pH Scale and Biological Relevance
The concentration of hydrogen ions (H+) in a solution determines its pH, which is critical for maintaining homeostasis in the body.
Acids: Substances that donate hydrogen ions, increasing H+ concentration and lowering pH.
Bases: Substances that accept hydrogen ions, decreasing H+ concentration and raising pH.
pH scale: Ranges from 0 (most acidic) to 14 (most alkaline), with 7 being neutral.
Equation:
Example: Human blood has a pH of about 7.4, which is slightly alkaline and tightly regulated.
pH Value | [H+] (moles/liter) | Example Substance |
|---|---|---|
0 | Concentrated HCl | |
2 | Lemon juice | |
4 | Tomatoes | |
7 | Human blood | |
9 | Baking soda | |
13 | Bleach |
Additional info: Maintaining proper pH is essential for enzyme activity and metabolic processes.
