[13] Radicals, Oxidative Stress, and Antioxidants - Biochemical Basis of Diseases

What are reactive oxygen species (ROS) and how does the body protect against their damage?

Reactive oxygen species (ROS) are highly damaging oxygen radicals such as superoxide (O₂⁻), hydroxyl (•OH), and perhydroxyl (•O₂H) that cause oxidative damage to tissues; the body protects against this damage using antioxidants

What is oxidative stress?

imbalance between excess free radicals (ROS) and insufficient antioxidants in the body

Why is oxygen considered a paradox in biological systems?

although oxygen is essential for energy metabolism, its partially reduced forms can damage cells and contribute to diseases such as aging, arthritis, and cancer

How does the body defend against oxidative stress and what types of antioxidants are involved?

The body defends against oxidative stress by producing antioxidants that neutralize free radicals;

antioxidant capacity is influenced by genetics and environmental factors like diet and smoking,

includes:

• endogenous antioxidants (enzymatic and non-enzymatic)

• exogenous antioxidants such as trace elements and drugs

What are 3 antioxidant defense systems?

• Inhibition of production of abundance RONS​

• Capture of radicals (scavengers, trappers, quenchers)​

• Correction mechanism of destroyed biomolecules

What are the important enzyme-catalyzed reactions?

What are high-molecular endogenous antioxidants?

• transferrin​

• ferritin​

• haptoglobin​

• hemopexin​

• albumin

What are low-molecular endogenous antioxidants?

• Ascorbic acid (vitamin C)​

• Tocopherol (vitamin E)​

• ubiquinone (coenzyme Q)​

• carotenoides, β-carotene, vitamin A​

• Glutathione​

• Lipoic acid ​

• melatonin​

• uric acid (urates)​

• bilirubin​

• flavonoids​