Biochemistry Foundations for Anatomy & Physiology

Biochemistry in Anatomy & Physiology

Introduction to Biochemistry

Biochemistry is the study of the chemical composition and reactions of living matter. It is fundamental to understanding the molecular basis of physiological processes in the human body. Compounds in biochemistry are classified into two main groups: organic and inorganic compounds.

• Organic Compounds: Contain carbon, are covalently bonded, often large, and essential for life. Examples include proteins, lipids, carbohydrates, and nucleic acids.

• Inorganic Compounds: Include all other chemicals in the body, also essential for life. Examples are water, salts, acids, and bases.

Organic Compounds

Characteristics and Examples

Organic compounds are defined by the presence of carbon atoms and covalent bonding. They are typically large molecules and play critical roles in cellular structure and function.

• Proteins: Serve as structural materials, enzymes, and signaling molecules.

• Lipids: Function in energy storage, membrane structure, and signaling.

• Carbohydrates: Provide energy and structural support.

• Nucleic Acids: Store and transmit genetic information.

Inorganic Compounds

Role in the Body

Inorganic compounds, though lacking carbon, are vital for physiological processes. They include water, salts, acids, and bases, each contributing to homeostasis and cellular function.

• Water: Most abundant inorganic compound, making up 60-80% of cell volume.

• Salts: Important for nerve impulse transmission and muscle contraction.

• Acids and Bases: Regulate pH and participate in metabolic reactions.

Water

Importance and Properties

Water is the most abundant and essential inorganic compound in the body, comprising 60-80% of cellular volume. Its unique properties make it indispensable for life.

• High Heat Capacity: Water absorbs and releases large amounts of heat with minimal temperature change, helping maintain homeostasis. Example: Sudden temperature changes from the sun are buffered by water redistributing heat among body tissues.

• High Heat of Vaporization: Large amounts of heat are required to break hydrogen bonds between water molecules. Example: Sweating removes heat from the body, providing a cooling mechanism.

• Polar Solvent: Water's polarity allows it to dissolve many substances, forming hydration layers around charged molecules. It serves as a transport medium for respiratory gases, metabolic wastes, and nutrients.

• Reactivity: Water participates as a reactant in many chemical reactions, including hydrolysis (decomposition) and dehydration synthesis (combination).

  • Hydrolysis Reaction: Water is used to split a substance into smaller molecules or atoms.

  • Dehydration Synthesis: Water is removed to form larger complex molecules, such as during the formation of lipids for energy storage and cellular repair.

• Cushioning: Water protects certain body organs from trauma, such as cerebrospinal fluid cushioning the brain.

Summary Table: Properties of Water

Property	Description	Physiological Importance
High Heat Capacity	Absorbs/releases heat with little temperature change	Maintains body temperature/homeostasis
High Heat of Vaporization	Requires much heat to evaporate	Enables cooling via sweating
Polar Solvent	Dissolves ionic/polar substances	Transports nutrients, gases, wastes
Reactivity	Participates in chemical reactions	Enables hydrolysis and synthesis
Cushioning	Protects organs from trauma	Protects brain, joints, etc.

Key Chemical Reactions Involving Water

Hydrolysis and Dehydration Synthesis

Water is central to two major types of biochemical reactions:

• Hydrolysis: A decomposition reaction where water is used to break bonds in larger molecules, producing smaller molecules. Equation: $\text{AB} + \text{H}_2\text{O} \rightarrow \text{AOH} + \text{BH}$

• Dehydration Synthesis: A combination reaction where water is removed to form a new bond between molecules, creating larger molecules. Equation: $\text{AOH} + \text{BH} \rightarrow \text{AB} + \text{H}_2\text{O}$

Conclusion

Understanding the chemical properties of water and the distinction between organic and inorganic compounds is foundational for studying anatomy and physiology. These principles explain how molecular interactions underpin physiological processes essential for life.