Anatomy & Physiology

Anatomy & Physiology Study Guide

©2018 Achieve Page 52 Water is a polar solvent and is the primary transport medium in the body. The pertinent properties of water include a high heat capacity and high heat of vaporization, meaning it can resist high heat before changes in temperature and state of matter. The ability of water to react in chemical reactions within the body and cushion organs makes it the most important solvent in human biology. 5.4 Electrolytes and Body Fluids Soluble inorganic molecules (molecules lacking carbon) whose ions will conduct an electrical current in solution are called electrolytes . Significant changes in electrolyte concentration within body fluids will disrupt almost every vital function. For example, declining potassium levels will lead to general muscular paralysis, and rising concentrations will cause weak and irregular heartbeats. The concentrations of ions in body fluids are carefully regulated, primarily by the coordination of activities at the kidneys (ion excretion), the digestive tract (ion absorption), and the skeletal system (ion storage or release). Body Fluid pH Levels A hydrogen atom involved in a chemical bond, or participating in a chemical reaction, can easily lose its electron to become a hydrogen ion ( H + ). Within solutions, hydrogen ions are very reactive. In excessive numbers, they will disrupt cell and tissue function, alter chemical bonds, and change the shapes of complex molecules. As a result, the concentration of hydrogen ions in body fluids must be regulated precisely. A few hydrogen ions are normally present even in a sample of pure water of 368 5.3 Types of Chemical Reactions Two types of chemical reactions are important to the study of physiology: decomposition reactions and synthesis reactions. Decomposition is a reaction that breaks a molecule into smaller fragments. Decomposition reactions occur outside and inside cells. For example, a typical meal contains molecules of fats, sugars, and proteins that are too large and too complex to be absorbed and used by the body. Decomposition reactions in the digestive tract break these molecules down into smaller fragments before absorption begins. Collectively, the decomposition reactions of complex molecules within the body’s cells and tissues are referred to as catabolism . AB → A + B Synthesis is the opposite of decomposition. A synthesis reaction assembles smaller molecules into larger molecules. Synthesis reactions may involve individual atoms or the combination of molecules to form even larger products. Dehydration synthesis , or condensation, occurs when complex molecules form by the removal of a water molecule. The synthesis of newmolecules within the body’s cells is anabolism . A + B → AB Water and Its Properties