ROS, Free Radicals Flashcards
What is important about the nature of Oxygen
Oxygen is a bi-radical. It supports life and bears toxicity. Oxygen toxicity results from reactive oxygen species and free radicals.
What are free Radicals?
Atomic or molecular species which are extremely reactive because they have an unpaired electron.
How are Reactive Oxygen Species generated?
By one-electron transfers.
Which mechanisms overlap with the antioxidant system, and are one of the biggest generators of free radicals?
Detoxification Mechanisms
Identify types Reactive Oxygen Species.
Superoxide Anion, Hydrogen Peroxide, Hydroxyl Radical, Organic Radical, Organic Peroxide Radical, Hypochlorous Acid, and Singlet Oxygen
What is the Fenton Reaction?
The decomposition of a metal (Fe2+) to produce Hydroxyl Radical and hydroxide ion.
Who is considered the “Bad Actor”
Mr. Hydroxyl Radical…he is the most destructive
What are some endogenous sources of free radicals in the body?
Enzyme Activity, Electron Transport Chain, Phagocytic Respiratory Burst
What are some exogenous sources of free radical?
UV Radiation, Drugs, air pollutants
What is a normal biological process that can generate superoxide?
The electron transport chain
What is the biggest offender in the electron transport chain in generating free radicals?
COQ…because it is not protected and it most abundant. COQ is reduced in an anaerobic state.
Why do some cells of the immune system purposely produce ROS?
To destroy bacteria
True or False? Lipids are not susceptible to free radical damage.
False
Oxidation involves the removal of ____ _____from unsaturated fatty acids.
Hydrogen radicals
Which Fatty Acids are most susceptible to oxidative damage?
Polyunsaturated Fatty Acids (PUFA)…monounsaturated FA are as well (ex. Olive Oil)
What are two types of free radical damage to PUFA?
- Decomposition to bi-functional aldehydes and/or alpha, beta-unsaturated aldehydes…which can form adducts or crosslink other biomolecules
- Reacting with Sulfhydryl groups on enzymes.
(refer to page 47 for reaction)
What are the 4 phases of the free radical damage mechanism?
Initiation, propagation, degradation, termination
What is an allylic radical?
a radical between double bonds. It is a more stable radical form. Electrons are not shared across all 3 carbons.
What is the 1st line of defense for cells to protect themselves against free radical damage/oxidative toxicity?
Antioxidant Enzymes: Glutathione peroxidase, superoxide dismutase, and catalase.
What is the 2nd line of defense for cells to protect themselves against free radical dmage and oxidative toxicity?
Vitamins E and C, and other free radical scavengers
What are the cellular locations?
Mitochondria, Peroxisomes, and Cytosol
What are the tissue Locations?
Liver (most abundant), adrenals, kidneys
In humans, the Cu, Zn superoxide dismutase is found where?
In the Cytosol
The Manganese SOD is found where?
In the mitochondrion
Ascorbic Acid aka…?
Vitamin C
Where does absorption of Vitamin C occur?
The distal small intestine through a sodium-dependent ascorbate transporter (SVCT)
True or false? Most cells acquire Vitamin C by SVCT2 or GLUT transporters.
True.
Which specific GLUT transporters do cells acquire Vitamin C?
GLUT 1 and GLUT 3
What does Ascorbate neutralize?
Radical Oxygen and Nitrogen Species, Peroxides and superoxides
True or false? The Ascorbate radical is very unstable.
False.
What reducing agents are involved in the regeneration of the reduced form of Vitamin C?
NADH or Glutathione
What are the enzymes that CAN be involved in the regeneration of the reduced form of Vitamin C? Of these, how many are required?
NADH reductase, Dehydroascorbate reductase, Thioredoxin reductase. At least one is required for the regeneration.
Vitamin C can go to Oxalic Acid, which will cause?
Kidney stones
Vitamin E helps protect?
Membranes and lipoproteins
True or false? The Vitamin E radical is stable.
True.
What does the Cellular Redox Cycle regenerate?
Reduced Vitamin E from reduced Vitamin C.
How does Vitamin E get exposed to Vitamin C?
On the surface of membranes
Which cycle resets the radical scavengers to their reduced form?
The Thiol Cycle
