Biochemistry Foundations for Anatomy & Physiology: Inorganic Compounds and Water

Biochemistry in Anatomy & Physiology

Introduction to Biochemistry

Biochemistry is the study of the chemical composition and reactions of living matter. Understanding biochemistry is essential for comprehending the structure and function of the human body at the molecular level.

• Organic compounds: Contain carbon, are usually large, and are covalently bonded. Examples include carbohydrates, fats (lipids), proteins, and nucleic acids.

• Inorganic compounds: Do not contain carbon (with some exceptions such as CO2 and CO). Examples include water, salts, acids, and bases.

• Both organic and inorganic compounds are essential for life.

Inorganic Compounds

Water

Water is the most abundant and important inorganic compound in living organisms, accounting for 60–80% of the volume of living cells. Its unique properties make it vital for life.

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

• High heat of vaporization: Evaporation of water requires significant energy, providing an effective cooling mechanism (e.g., sweating).

• Polar solvent properties: Water dissolves and dissociates ionic substances and forms hydration layers around large charged molecules (such as proteins), making it the body's major transport medium.

• Reactivity: Water is involved in many chemical reactions, including hydrolysis and dehydration synthesis.

• Cushioning: Water protects organs from physical trauma. For example, cerebrospinal fluid cushions the brain and spinal cord.

Example: Dissociation of Salt in Water

When salt (NaCl) is added to water, the polar water molecules surround and separate the sodium (Na+) and chloride (Cl-) ions, allowing them to disperse throughout the solution. This process is essential for the conduction of electrical signals in the body.

Salts

Salts are ionic compounds that dissociate into separate ions in water (excluding H+ and OH- ions). They play critical roles in physiological processes.

• Salts separate into cations (positively charged ions) and anions (negatively charged ions).

• All ions in solution are called electrolytes because they conduct electrical currents.

• Electrolyte balance is vital for homeostasis, affecting nerve impulse transmission, muscle contraction, and water balance.

• Common body salts include sodium chloride (NaCl), potassium chloride (KCl), calcium carbonate (CaCO3), and calcium phosphates.

Table: Properties and Functions of Water in the Body

Property	Description	Physiological Importance
High heat capacity	Absorbs/releases heat with little temperature change	Maintains stable body temperature
High heat of vaporization	Requires much energy to evaporate	Enables cooling via perspiration
Polar solvent	Dissolves ionic and polar substances	Facilitates transport and chemical reactions
Reactivity	Participates in hydrolysis and synthesis	Essential for metabolism
Cushioning	Absorbs impact	Protects organs (e.g., brain, spinal cord)

Key Terms

• Hydrolysis: A chemical reaction in which water is used to break down a compound.

• Dehydration synthesis: A chemical reaction in which two molecules are joined by removing a molecule of water.

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

Additional info: The above content is foundational for understanding the chemical basis of physiological processes, including nerve conduction, muscle contraction, and cellular metabolism, which are covered in later chapters of Anatomy & Physiology.