Bioinorganic Chemistry: Elements in Life

Bioinorganic chemistry explores the vital roles of inorganic elements in living systems. One crucial area, often studied by students preparing for Bioinorganic Chemistry: Elements in Life exams, involves the delicate balance of reactive species and antioxidant defenses within the body. While oxygen is essential for life, it can also lead to the formation of reactive metabolites (RM) that can be harmful. This article provides a comprehensive summary and analysis of these oxidants, antioxidants, and the concept of oxidative stress, drawing directly from medical chemistry study materials.

Bioinorganic Chemistry: Understanding Reactive Metabolites and Free Radicals

Life depends on oxygen, yet oxygen can also be harmful. Its toxic effects stem from its ability to undergo one-electron reduction to form the superoxide anion radical (O2•–), which then leads to other reactive metabolites (RM). These reactive compounds are collectively known as reactive oxygen/nitrogen species (ROS/RNS) and are produced during both physiological and pathological processes. Free radicals are atoms, molecules, or fragments with one or more unpaired electrons, capable of independent existence for a short time. They are highly reactive oxidants that can cause damage by taking electrons from other compounds.

Sources of free radical formation can be internal or external:

Internal Sources:

• Phagocytes
• Mitochondria
• Peroxisomes
• Ischemic-reperfusion conditions
• Reactions catalyzed by xanthine oxidase
• Arachidonic acid cascade reactions
• Reactions involving transition metal ions
• Inflammation
• Extreme exercise

External Sources:

• Cigarette smoke
• Environmental pollution
• Radiation
• Chemotherapeutics
• Ultraviolet light
• Some medicines, pesticides, anesthetics, organic solvents
• Ozone

Types of Reactive Oxygen Species (ROS)

ROS is a broad term encompassing both oxygen radicals and certain non-radicals (like HOCl, HOBr, O3, ONOO, 1O2, and H2O2) that act as oxidizing agents or convert into radicals. While all oxygen radicals are ROS, not all ROS are oxygen radicals. The main types include:

Superoxide Anion Radical (O2•–)

Superoxide is formed naturally in the body:

• As a product of physiological processes (e.g., in neutrophils during phagocytosis, by NADPH-oxidase: NADPH + O2 → NADP+ + H+ + O2•–).
• As a