Fundamentals of Chemistry in Anatomy & Physiology: Organic, Inorganic Compounds, Water, Acids, Bases, and pH

Basic Chemistry in Anatomy & Physiology

Introduction to Chemistry in Living Systems

Chemistry is fundamental to understanding the structure and function of living organisms. In anatomy and physiology, the study of chemical composition and reactions is essential for grasping how biological processes occur.

• Organic compounds contain carbon and include carbohydrates, lipids, proteins, and nucleic acids.

• Inorganic compounds include water, salts, and many acids and bases; most do not contain carbon.

• Organic compounds are usually large and covalently bonded, and are essential for life.

Inorganic Compounds

Water: The Most Important Inorganic Compound

Water makes up 60–80% of the volume of living cells and is vital due to its unique properties.

• High heat capacity: Water can absorb and release large amounts of heat with little temperature change, helping to stabilize body temperature.

• High heat of vaporization: Evaporation of water requires significant energy, which is important for cooling mechanisms such as sweating.

• Polar solvent properties: Water dissolves ionic substances and forms hydration layers around large charged molecules (e.g., proteins), making it an excellent transport medium.

• Reactivity: Water is involved in hydrolysis and dehydration synthesis reactions, which are essential for building and breaking down biological molecules.

• Cushioning: Water protects organs from physical trauma; for example, cerebrospinal fluid cushions nervous system organs.

Properties of Water

Thermal and Solvent Properties

• High heat capacity: Water resists sudden changes in temperature, maintaining homeostasis.

• High heat of vaporization: Large amounts of heat are needed to evaporate water, aiding in temperature regulation.

• Polar solvent properties: Water dissociates ionic substances and forms hydration layers around charged molecules, facilitating transport and chemical reactions.

Salts, Acids, and Bases

Salts

Salts are ionic compounds that dissociate into ions in water. These ions are called electrolytes because they conduct electrical currents in solution and play specialized roles in body functions.

• Cations: Positively charged ions (e.g., Na+, K+, Ca2+).

• Anions: Negatively charged ions (e.g., Cl-, HCO3-).

• Electrolyte balance is vital for homeostasis.

• Examples of salts: NaCl (sodium chloride), KCl (potassium chloride), calcium phosphates.

Acids

Acids are substances that release hydrogen ions (H+) in solution and are considered proton donors. They are electrolytes and dissociate in water.

• Common acids: HCl (hydrochloric acid), HC2H3O2 (acetic acid), H2CO3 (carbonic acid).

• Acids increase the concentration of H+ ions, lowering pH.

Bases

Bases are substances that accept hydrogen ions (H+) and are considered proton acceptors. When dissolved in water, bases release hydroxyl ions (OH-).

• Common bases: Bicarbonate ion (HCO3-), ammonia (NH3).

• Bases decrease the concentration of H+ ions, raising pH.

Acids and Bases: pH

pH Scale and Measurement

The pH scale measures the concentration of hydrogen ions in a solution. It is logarithmic, so each pH unit represents a tenfold difference in H+ concentration.

• pH formula:

$pH = -\log_{10}[H^+]$

• pH range: 0 (most acidic) to 14 (most basic).

• Neutral solutions have a pH of 7 (e.g., pure water).

• Acidic solutions: pH < 7; Basic (alkaline) solutions: pH > 7.

• Body fluids must maintain a narrow pH range for proper function.

Acids and Bases: Neutralization and Buffers

Neutralization Reactions

When acids and bases are mixed, they react to form water and a salt, neutralizing each other.

• General reaction:

$\text{Acid} + \text{Base} \rightarrow \text{Salt} + \text{Water}$

• Example: $\text{NaOH} + \text{HCl} \rightarrow \text{NaCl} + \text{H}_2\text{O}$

Buffers

Buffers are systems composed of a weak acid and a weak base that resist large swings in pH by releasing or binding hydrogen ions as needed.

• Function: Buffers convert strong acids or bases into weak ones to maintain pH balance.

• Example: The bicarbonate buffer system is important in blood to maintain pH homeostasis.

Summary Table: Properties of Water

Property	Description	Physiological Importance
High Heat Capacity	Absorbs/releases heat with little temperature change	Helps maintain stable body temperature
High Heat of Vaporization	Requires large amounts of heat to evaporate	Enables cooling via sweating
Polar Solvent Properties	Dissolves ionic substances, forms hydration layers	Facilitates transport and chemical reactions
Reactivity	Participates in hydrolysis and dehydration synthesis	Essential for metabolism
Cushioning	Protects organs from trauma	Cerebrospinal fluid cushions brain and spinal cord

Summary Table: Acids, Bases, and Salts

Type	Definition	Examples	Role in Body
Acid	Releases H+ ions (proton donor)	HCl, HC2H3O2, H2CO3	Regulates pH, digestion
Base	Accepts H+ ions (proton acceptor)	HCO3-, NH3	Regulates pH, neutralizes acids
Salt	Dissociates into ions (electrolytes)	NaCl, KCl, Ca3(PO4)2	Electrolyte balance, nerve/muscle function

Key Terms and Definitions

• Electrolyte: A substance that conducts electricity when dissolved in water due to the presence of ions.

• Hydrolysis: A chemical reaction that breaks bonds by adding water.

• Dehydration synthesis: A chemical reaction that forms bonds by removing water.

• Buffer: A system that resists changes in pH.

• pH: A measure of hydrogen ion concentration; indicates acidity or alkalinity.

Examples and Applications

• Example: Blood pH is tightly regulated between 7.35 and 7.45 by buffer systems.

• Application: Electrolytes such as sodium and potassium are essential for nerve impulse transmission and muscle contraction.

Additional info: Some content was inferred and expanded for completeness and clarity, including definitions, physiological relevance, and example equations.