ROS, Free Radicals

Question 1

What is important about the nature of Oxygen

Answer 1

Oxygen is a bi-radical. It supports life and bears toxicity. Oxygen toxicity results from reactive oxygen species and free radicals.

Question 2

What are free Radicals?

Answer 2

Atomic or molecular species which are extremely reactive because they have an unpaired electron.

Question 3

How are Reactive Oxygen Species generated?

Answer 3

By one-electron transfers.

Question 4

Which mechanisms overlap with the antioxidant system, and are one of the biggest generators of free radicals?

Answer 4

Detoxification Mechanisms

Question 5

Identify types Reactive Oxygen Species.

Answer 5

Superoxide Anion, Hydrogen Peroxide, Hydroxyl Radical, Organic Radical, Organic Peroxide Radical, Hypochlorous Acid, and Singlet Oxygen

Question 6

What is the Fenton Reaction?

Answer 6

The decomposition of a metal (Fe2+) to produce Hydroxyl Radical and hydroxide ion.

Question 7

Who is considered the “Bad Actor”

Answer 7

Mr. Hydroxyl Radical…he is the most destructive

Question 8

What are some endogenous sources of free radicals in the body?

Answer 8

Enzyme Activity, Electron Transport Chain, Phagocytic Respiratory Burst

Question 9

What are some exogenous sources of free radical?

Answer 9

UV Radiation, Drugs, air pollutants

Question 10

What is a normal biological process that can generate superoxide?

Answer 10

The electron transport chain

Question 11

What is the biggest offender in the electron transport chain in generating free radicals?

Answer 11

COQ…because it is not protected and it most abundant. COQ is reduced in an anaerobic state.

Question 12

Why do some cells of the immune system purposely produce ROS?

Answer 12

To destroy bacteria

Question 13

True or False? Lipids are not susceptible to free radical damage.

Answer 13

False

Question 14

Oxidation involves the removal of ____ _____from unsaturated fatty acids.

Answer 14

Hydrogen radicals

Question 15

Which Fatty Acids are most susceptible to oxidative damage?

Answer 15

Polyunsaturated Fatty Acids (PUFA)…monounsaturated FA are as well (ex. Olive Oil)

Question 16

What are two types of free radical damage to PUFA?

Answer 16

1. Decomposition to bi-functional aldehydes and/or alpha, beta-unsaturated aldehydes…which can form adducts or crosslink other biomolecules
2. Reacting with Sulfhydryl groups on enzymes.
   (refer to page 47 for reaction)

Question 17

What are the 4 phases of the free radical damage mechanism?

Answer 17

Initiation, propagation, degradation, termination

Question 18

What is an allylic radical?

Answer 18

a radical between double bonds. It is a more stable radical form. Electrons are not shared across all 3 carbons.

Question 19

What is the 1st line of defense for cells to protect themselves against free radical damage/oxidative toxicity?

Answer 19

Antioxidant Enzymes: Glutathione peroxidase, superoxide dismutase, and catalase.

Question 20

What is the 2nd line of defense for cells to protect themselves against free radical dmage and oxidative toxicity?

Answer 20

Vitamins E and C, and other free radical scavengers

Question 21

What are the cellular locations?

Answer 21

Mitochondria, Peroxisomes, and Cytosol

Question 22

What are the tissue Locations?

Answer 22

Liver (most abundant), adrenals, kidneys

Question 23

In humans, the Cu, Zn superoxide dismutase is found where?

Answer 23

In the Cytosol

Question 24

The Manganese SOD is found where?

Answer 24

In the mitochondrion

Question 25

Ascorbic Acid aka...?

Answer 25

Vitamin C

Question 26

Where does absorption of Vitamin C occur?

Answer 26

The distal small intestine through a sodium-dependent ascorbate transporter (SVCT)

Question 27

True or false? Most cells acquire Vitamin C by SVCT2 or GLUT transporters.

Answer 27

True.

Question 28

Which specific GLUT transporters do cells acquire Vitamin C?

Answer 28

GLUT 1 and GLUT 3

Question 29

What does Ascorbate neutralize?

Answer 29

Radical Oxygen and Nitrogen Species, Peroxides and superoxides

Question 30

True or false? The Ascorbate radical is very unstable.

Answer 30

False.

Question 31

What reducing agents are involved in the regeneration of the reduced form of Vitamin C?

Answer 31

NADH or Glutathione

Question 32

What are the enzymes that CAN be involved in the regeneration of the reduced form of Vitamin C? Of these, how many are required?

Answer 32

NADH reductase, Dehydroascorbate reductase, Thioredoxin reductase. At least one is required for the regeneration.

Question 33

Vitamin C can go to Oxalic Acid, which will cause?

Answer 33

Kidney stones

Question 34

Vitamin E helps protect?

Answer 34

Membranes and lipoproteins

Question 35

True or false? The Vitamin E radical is stable.

Answer 35

True.

Question 36

What does the Cellular Redox Cycle regenerate?

Answer 36

Reduced Vitamin E from reduced Vitamin C.

Question 37

How does Vitamin E get exposed to Vitamin C?

Answer 37

On the surface of membranes

Question 38

Which cycle resets the radical scavengers to their reduced form?

Answer 38

The Thiol Cycle