free radicals

What is a free radical?

Any atom with at least one unpaired electron in the outermost shell.

Why are free radicals highly reactive?

Because of the presence of an unpaired electron.

What happens when a free radical "steals" an electron from another nearby atom?

The original free radical becomes stable, but the neighboring atom becomes a free radical.

What does a new free radical do after it has formed?

It seeks out another atom to steal from, creating a chain reaction.

What are some examples of free radicals?

Oxygen free radical (O2-), Hydroxyl free radical (OH•), Nitric oxide free radical (NO•), Lipid peroxide free radical (LOO•).

What are antioxidants?

Substances that can neutralize free radicals by donating electrons without becoming free radicals themselves.

How do antioxidants help combat free radical damage?

They prevent the chain reaction of free radical formation by providing electrons to stabilize free radicals.

What are the types of reactive oxygen species (oxygen-derived free radicals)?

Superoxide anion (O2-), Hydrogen peroxide (H2O2), Hydroxyl radical (OH•)

What are the types of nitrogen oxides?

Nitric oxide (NO•), Nitrogen dioxide (NO2•)

What are the types of lipid-derived free radicals?

Lipid peroxide, Conjugates, Hydroperoxide (LOOH)

What are xenobiotic-derived free radicals derived from?

Chemicals, drugs, and toxins

What is an example of a xenobiotic-derived free radical?

Lipid peroxide

What are some endogenous sources of free radicals?

Mitochondrial or microsomal cytochrome oxidases, Oxidases and oxygenases (e.g., Xanthine oxidase), Activation of immune system cells like neutrophils (utilizing NADPH oxidase and myeloperoxidase), Autooxidation reactions (e.g., epinephrine by MAO), Transitional metals (e.g., free copper and iron).

What is an example of an endogenous source of free radicals in cells?

Xanthine oxidase

Which immune system cells utilize NADPH oxidase and myeloperoxidase as sources of free radicals?

Neutrophils

What is an example of an autooxidation reaction that generates free radicals?

Epinephrine by MAO (Monoamine oxidase)

Which transitional metals can act as sources of free radicals within cells?

Free copper and iron

What are some exogenous sources of free radicals?

1. Cigarette smoke. 2. Hyperoxia. 3. Ozone (O3). 4. Ionizing radiation (X- and γ-rays). 5. Oxidizing xenobiotics (e.g., high dose of paracetamol). 6. Non-ionizing radiation (e.g., UV rays). 7. Heat shock. 8. Burning and peroxidative products of food cooking. 9. Incomplete ignition of fuel materials.

Which environmental factor can contribute to the generation of free radicals through incomplete ignition?

Incomplete ignition of fuel materials

What is a common source of ionizing radiation that can produce free radicals?

X- and γ-rays

What type of radiation is associated with UV rays as an exogenous source of free radicals?

Non-ionizing radiation

What are some products of food cooking that can produce free radicals?

Burning and peroxidative products

What are some damaging effects of free radicals?

A- DNA damage (i.e., mutation). B- Damage to Lipids (i.e., Lipid peroxidation). C- Protein damage (i.e., denaturation).

How can free radicals damage DNA?

By causing mutations

What is the result of damage to lipids by free radicals?

Lipid peroxidation

What happens to proteins when exposed to free radicals?

Denaturation

What are some beneficial effects of free radicals?

Certain cells in the immune system engulf bacteria or viruses and create a flood of reactive oxygen species (ROS) using enzymes like NADPH oxidase and myeloperoxidase.

How do reactive oxygen species (ROS) produced by immune cells help the body?

They are remarkably effective in protecting the body against infectious organisms.

What types of damage are included in DNA damage caused by free radicals?

1. Single and double strand breaks. 2. Base damage (e.g., 8-deoxy-hydroxy guanosine). 3. Sugar damage. 4. DNA-DNA and DNA-protein cross links.

What are the consequences of these DNA damages caused by free radicals?

These damages can lead to mutation, followed by cytotoxicity (cell death), cellular transformation into cancer, or teratogenesis.

What is lipid peroxidation?

Lipid peroxidation is the peroxidative damage of polyunsaturated fatty acids (PUFAs) in cell membranes and other organized systems due to their reaction with toxic free radicals.

What is another term for in vitro lipid peroxidation?

In vitro lipid peroxidation is also referred to as "rancidity," and one of its markers is Malondialdehyde (MDA).

How does free radical damage affect proteins and enzymes?

1. Oxidation of SH groups at the active site of many enzymes and proteins, leading to inactivation, such as carbonyl proteins. 2. Denaturation of structural proteins, which can result in cell death.

What happens when SH groups in the active site of enzymes and proteins are oxidized by free radicals?

It leads to inactivation of these enzymes and proteins, often resulting in the formation of carbonyl proteins.

How can protein denaturation caused by free radicals impact cells?

Protein denaturation can lead to cell death.

What is the definition of an antioxidant?

An antioxidant is any substance or mechanism that prevents the generation of free radicals, scavenges free radicals, or repairs damage induced by free radicals.

How are antioxidants grouped based on their mechanism of action?

Antioxidants are grouped into three main types based on their mechanism of action.

What are primary antioxidants (preventive antioxidants)?

Primary antioxidants are antioxidants that prevent the generation of free radicals.

Name two subcategories of primary antioxidants and provide examples for each.

A) Chelating proteins: Examples include ferritin and transferrin for iron, and ceruloplasmin for copper. B) Enzymatic antioxidants: Examples include Superoxide dismutase (SOD), Catalase, and Glutathione peroxidase (GPX), which is selenium-dependent.

What are secondary antioxidants (chain-breaking antioxidants)?

Secondary antioxidants are antioxidants that scavenge free radicals and break the chain of their propagation.

Name some examples of secondary antioxidants.

Examples of secondary antioxidants include vitamin E, vitamin A, vitamin C, and non-vitamin antioxidants like uric acid, bilirubin, glucose, and proteins.

What are tertiary antioxidants (reparative antioxidants)?

Tertiary antioxidants are antioxidants that repair the damage that has occurred to the target molecules or replace them with new ones.

What are examples of tertiary antioxidants?

Examples of tertiary antioxidants include DNA repair enzymes and lysosomal enzymes.

What is the definition of oxidative stress?

Oxidative stress is the condition where the generation of oxidant free radicals and the level of antioxidant defense systems are approximately balanced, resulting in an imbalance of oxidant free radicals/antioxidant systems.

Which diseases involve ischemic injury in the heart and brain?

Ischemic injury: heart and brain.

Which category of diseases includes respiratory diseases involving oxidative stress?

Respiratory diseases.

What are some diseases associated with oxidative stress in the form of cancer development?

Cancers.

Which group of diseases encompasses gastrointestinal diseases with oxidative stress implications?

Gastrointestinal diseases.

Oxidative stress is linked to which type of diseases related to the blood and blood-forming tissues?

Hematological diseases.

What types of diseases are classified under immunological diseases involving oxidative stress?

Immunological diseases.

Which metabolic disorder is known to be associated with oxidative stress?

Diabetes mellitus.

Oxidative stress is implicated in which category of diseases affecting the nervous system?

Neurological diseases.

What are some diseases of the eye that involve oxidative stress?

Eye diseases.

In which medical condition does oxidative stress play a role in renal failure?

Renal failure.

What vascular condition is associated with oxidative stress?

Atherosclerosis.

What biological process is linked to diseases related to aging and oxidative stress?

Aging.

In the context of reproductive health, what condition involves oxidative stress?

Male infertility.