Introduction

The study of free Radicals has received a considerable lot of attention recently. Free radicals’ like, reactive oxygen species and reactive nitrogen species are generated by our body by various endogenous systems and exposure to different physio chemical conditions or pathological states.

Our body also has antioxidants to counteract free radicals. For better health, a balance between free radicals and antioxidants is necessary for proper physiological function.

If free radical formation exceeds then the body’s ability to regulate them, then there is an imbalance between free radicles and antioxidants. This means the body does not have sufficient antioxidants to neutralize free radicles. This condition is called as Oxidative Stress.

Free radicals thus adversely alter lipids, proteins, and DNA and trigger a number of human diseases, especially chronic diseases. To know more about chronic diseases read the blog article;What are chronic diseases? Hence the application or use of external sources of antioxidants can assist in coping with this oxidative stress.

In this article, you will learn about free radicles, oxidative stress, and how it affects the functioning of the body cells. So, there is a direct relationship between functioning of the body cells and diseases.

What are free radicals?

A free radical can be defined as any molecular species capable of independent existence that contains an unpaired electron in its outermost electron orbit.

This unpaired electron makes free radicals highly unstable and eager to react with other molecules in an attempt to gain stability.

Free radicals are also known as oxidants.

They can either donate an electron to or accept an electron from other molecules, therefore behaving as oxidants or reductants.

These free radicals are produced in our normal body, especially in the mitochondria where most of the energy is produced in the form of ATP.

In the process, free radicals can Damage cellular structures, including proteins, lipids, and DNA, leading to oxidative stress and potentially contributing to various diseases and aging. The cellular function is affected and the endogenously present antioxidant nutrients get depleted causing nutrient deficiency.

Why free radicals are produced in the body?

Free radicals can be generated both endogenously (within the body) and exogenously (from external sources). Some common sources of free radicals include:

1) Endogenous Sources:

1. Mitochondrial respiration: During the process of generating energy within cells, some oxygen molecules can convert into free radicals.
2. Inflammatory responses: Certain immune cells produce free radicals to combat infections and pathogens.
3. Enzymatic reactions: Some enzymes in the body can produce free radicals as part of their normal function.

2) Exogenous Sources:

1. Environmental pollutants: Exposure to air pollution, radiation, and other environmental toxins can lead to the formation of free radicals.
2. Cigarette smoke: Smoking introduces a significant amount of free radicals into the body.
3. Ultraviolet (UV) radiation: Sunlight and tanning beds can generate free radicals in the skin.

The body has natural defense mechanisms against free radicals, including antioxidants. Antioxidants are molecules that neutralize free radicals by donating electrons without becoming unstable themselves. The body produces some antioxidants, while others are obtained from the diet through various fruits, vegetables, and other foods.

Free Radicals Produced in the Body and Their Chemical Structures:

1. Hydroxyl radical (OH•): Formed during various cellular processes, such as the Fenton reaction involving iron and hydrogen peroxide. The hydroxyl radical is one of the most potent and damaging free radicals.
2. Superoxide anion radical (O2•-): Generated during aerobic metabolism, particularly in the electron transport chain of the mitochondria.
3. Nitric oxide radical (NO•): A signaling molecule produced by endothelial cells, neurons, and other cell types. It can act as a free radical and play a role in various physiological processes.
4. Peroxyl radical (ROO•): Formed during the auto-oxidation of lipids, which is a chain reaction leading to lipid peroxidation.
5. Alkoxyl radical (RO•): Derived from peroxyl radicals during lipid peroxidation processes.
6. Singlet oxygen (^1O2): Formed during photosynthesis and certain biochemical reactions.

What are these natural antioxidants present in the body?

Here are some of the most common antioxidants in the body, classified as vitamins, minerals, and enzymic antioxidants:

Vitamin antioxidants

• Vitamin C: Vitamin C is a powerful antioxidant that helps to protect cells from damage. It is found in many fruits and vegetables, such as citrus fruits, broccoli, and bell peppers.
• Vitamin E: Vitamin E is another powerful antioxidant that helps to protect cells from damage. It is found in many oils, nuts, and seeds, such as olive oil, almonds, and sunflower seeds.
• Beta-carotene: Beta-carotene is a carotenoid that is converted into vitamin A in the body. It is a powerful antioxidant that helps to protect cells from damage. It is found in many orange and yellow fruits and vegetables, such as carrots, sweet potatoes, and cantaloupe.
• Lutein and zeaxanthin: Lutein and zeaxanthin are carotenoids that are found in the retina of the eye. They help to protect the eyes from damage caused by free radicals. They are found in many green leafy vegetables, such as spinach and kale.

Mineral antioxidants

• Selenium: Selenium is a trace mineral that is important for the production of antioxidant enzymes. It is found in many seafood, meat, and poultry.
• Zinc: Zinc is a trace mineral that is important for the production of antioxidant enzymes. It is found in many meat, poultry, and seafood.
• Manganese: Manganese is a trace mineral that is important for the production of antioxidant enzymes. It is found in many fruits, vegetables, and whole grains.

Enzymic antioxidants

• Superoxide dismutase (SOD): SOD is an enzyme that helps to break down superoxide radicals, one of the most harmful types of free radicals. It is found in all cells in the body.
• Catalase: Catalase is an enzyme that helps to break down hydrogen peroxide, another harmful type of free radical. It is found in high concentrations in the liver and kidneys.
• Glutathione peroxidase (GPx): GPx is an enzyme that helps to break down peroxides, a type of free radical that is produced by the body during metabolism. It is found in all cells in the body.

Oxidative Stress and Diseases

Oxidative stress is a phenomenon caused by an imbalance between the production and accumulation of oxygen reactive species (ROS) in cells and tissues and the ability of a biological system to detoxify these reactive products. The number of free radicles produced is more and the antioxidants available to neutralize them are less. This means some free radicles cannot be neutralized. These free radicles then cause damage to the cell membranes and other parts of the cells. This also means that there is a deficiency of antioxidants in the body.

How do free radicles damage our bodies?

What is the mechanism of damage by free radicles?  Basically, free radicles are highly reactive species because they contain an unpaired.

Whenever there is an unpaired electron, what we can expect? It will cause oxidation or reduction? Whenever there is an unpaired electron in the outer orbit, it will cause oxidation. They will cause oxidative damage:

• Oxidative damage of cell membranes;
• Damage cytoplasmic proteins;
• Damage nuclear membrane;
• Damage the DNA which is present inside the nuclear membrane; (mutation)
• This damage by free radicles is also responsible for aging.

This oxidative stress has been linked to various diseases and conditions, including:

• Cardiovascular diseases: Atherosclerosis and other heart-related conditions.
• Neurodegenerative disorders: Alzheimer’s disease, Parkinson’s disease, etc.
• Cancer: Oxidative damage to DNA can contribute to the development of cancer.
• Aging: Oxidative stress is believed to play a role in the aging process.

While free radicals are associated with damaging effects, they also serve essential roles in the body. For example, immune cells use free radicals to destroy pathogens, and nitric oxide, a free radical, plays a crucial role in blood vessel dilation and other physiological functions.

To maintain a healthy balance, it’s essential to adopt a balanced diet rich in antioxidants, avoid smoking and excessive exposure to environmental pollutants, and manage stress effectively. A lifestyle that supports the body’s natural antioxidant defenses can help mitigate the negative impact of free radicals on overall health and well-being.

Free Radicals affect Cellular Function:

Free radicals can, in fact, have a major impact on cellular activity. Free radicals are very reactive molecules with unpaired electrons that can start a chain reaction that damages cells. Free radicals can interfere with vital cellular functions and produce a number of harmful effects when they interact with cellular building blocks such as proteins, lipids, and DNA.

Protein Damage: Free radicals can modify amino acids in proteins, leading to misfolding and loss of protein function. This can affect the structure and function of enzymes, receptors, and other proteins critical for cellular processes.

Lipid Peroxidation: Free radicals can attack lipids (fats) in cell membranes, causing lipid peroxidation. This process creates lipid radicals that, in turn, propagate further damage, leading to membrane dysfunction and cell integrity issues.

DNA Damage: One of the most concerning effects of free radicals is their ability to damage DNA. This can lead to mutations, genetic instability, and impaired DNA repair mechanisms, increasing the risk of cancer and other diseases.

Oxidative Stress: When there is an imbalance between free radicals and the body’s antioxidant defenses, oxidative stress occurs. Excessive free radical production overwhelms the antioxidant capacity, leading to further cellular damage and dysfunction.

Mitochondrial Dysfunction: Mitochondria are the energy-producing organelles in cells. Free radicals can target and damage mitochondrial DNA and proteins, disrupting energy production and impairing cellular function.

Inflammation: Free radicals can activate inflammatory pathways, leading to chronic inflammation. Inflammatory responses, when prolonged, can contribute to various diseases and accelerate cellular aging.

Cellular Aging: The cumulative effects of free radical damage on cellular components can accelerate the aging process, known as cellular or biological aging. This contributes to age-related diseases and conditions.

Cell Signaling Alterations: Free radicals can interfere with cell signaling pathways, affecting various cellular responses, such as growth, differentiation, and apoptosis (cell death).

Impaired Immune Function: Oxidative stress can weaken immune responses, making the body more susceptible to infections and impairing immune system efficiency.

Conclusion

Overall, the negative effects of free radicals on cellular activity highlight the significance of preserving a balance between free radical generation and antioxidant defenses.

A healthy lifestyle, including a diet rich in antioxidants, regular exercise, stress management, and avoiding harmful habits like smoking and excessive alcohol consumption, can help reduce free radical-induced cellular damage and promote overall cellular health.

Supplementing with antioxidant vitamins like vitamin A,C & E may also be essential.

References

Free radicals, antioxidants and functional foods: Impact on human health: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3249911/

An introduction to free radical biochemistry: https://pubmed.ncbi.nlm.nih.gov/8221017/

Free radicals and antioxidants: human physiology, pathology and therapeutic aspects: https://pubmed.ncbi.nlm.nih.gov/9437876/

Free Radicals: Definition, Cause, and Role in Cancer: https://www.verywellhealth.com/information-about-free-radicals-2249103

Bagchi K, Puri S. Free radicals and antioxidants in health and disease. East Mediterranean Health Jr. 1998;4:350–60: https://apps.who.int/iris/bitstream/handle/10665/118217/emhj_1998_4_2_350_360.pdf?sequence=1

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