Questions and Answers
What is the definition of a free radical?
A molecule with one or more unpaired electrons in its outer orbital
What are the products of the partial reduction of oxygen that are highly reactive?
Superoxide anion radical, hydroperoxyl radical, hydrogen peroxide, hydroxyl radical, lipid peroxide radical
What are the important characteristics of reactive oxygen species (ROS)?
Extreme reactivity, short life span, generation of new ROS by chain reaction, damage to various tissues
What is the percentage of oxygen taken up in the body that is converted to free radicals?
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Which type of anti-oxidants can inhibit the initial production of free radicals?
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What role do preventive anti-oxidants play in the process of lipid peroxidation?
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What is the primary event during the initiation phase of lipid peroxidation?
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Which of the following is a chain breaking anti-oxidant?
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What is the net result of reactions 2 and 3 during the propagation phase of lipid peroxidation?
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Which anti-oxidant is the aqueous phase antioxidant?
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What produces superoxide anion by a process of respiratory burst during phagocytosis?
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Which enzyme is responsible for producing nitric oxide (NO) from arginine?
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What can cause photolysis of oxygen to produce singlet oxygen?
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Which enzyme is manganese dependent and is involved in scavenging superoxide radicals?
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What enzyme is used for the removal of H2O2 when it is generated in large quantities?
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What is the clinical significance of chronic inflammatory diseases like rheumatoid arthritis?
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What is the cause of retrolental fibroplasia (retinopathy of prematurity) in premature infants treated with pure oxygen for a long time?
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What is the cause of reperfusion injury after myocardial ischemia?
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What causes low-density lipoproteins (LDL) to be deposited under the endothelial cells, leading to atherosclerosis?
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How is shock-related injury caused?
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What protective effect do antioxidants have in shock-related injury?
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How are plant products used in the treatment of psoriasis and leukoderma related to free radicals?
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Study Notes
- Free radicals are highly reactive molecules or fragments with unpaired electrons in their outer orbital.
- They are continuously produced during normal metabolic processes, as well as in response to external stimuli such as oxygen radicals, light, or certain enzymes.
- Reactive oxygen species (ROS) include superoxide anion radical (O2--), hydroperoxyl radical (HOO), hydrogen peroxide (H2O2), hydroxyl radical (OH), lipid peroxide radical (ROO), singlet oxygen (1O2), nitric oxide (NO), and peroxy nitrite (ONOO).
- ROS can damage various tissues, including the membranes of cells, lipids, proteins, and DNA.
- Free radicals can be produced by the body's own metabolic processes, such as in the electron transport chain, or by external factors like oxidizing agents, cigarette smoke, or air pollutants.
- The body has various systems to scavenge and neutralize free radicals, including superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase, and glutathione reductase (GR).
- Damage caused by free radicals can lead to various diseases and conditions, such as chronic inflammation, acute inflammation, respiratory diseases, eye diseases, reperfusion injury, atherosclerosis and myocardial infarction, shock-related injury, skin diseases, carcinogenesis, and aging.
- Free radicals can damage DNA, leading to somatic mutations and malignancy.
- Lipid peroxidation is a process by which free radicals damage lipids, leading to the formation of hydroperoxides and other damaging compounds.
- Preventive anti-oxidants, such as catalase, glutathione peroxidase, and ethylene diamine tetra-acetate (EDTA), inhibit the initial production of free radicals.
- Chain breaking anti-oxidants, such as superoxide dismutase, uric acid, vitamin E, and other compounds, can inhibit the propagation of free radical reactions.
- Vitamin E is the primary lipid-soluble antioxidant, while vitamin C is the primary water-soluble antioxidant.
- Other compounds, such as caffeine, cysteine, glutathione, and vitamin A, also have antioxidant properties.
