Lecture 20

Question 1

What species is the most potent ROS in biological systems?

Answer 1

Hydroxyl Radical: OH.

Question 2

What is the function of Superoxie Dismutase?

Answer 2

Gets rid of Superoxide by making Oxygen and Hydrogen Peroxide in place (Hydrogen peroxide also needs to be removed)

Question 3

What does compartmentation mean in terms of cellular defense?

Answer 3

Method of cellular defense where
1. Enzymes producing hydrogen peroxides are sequestered in peroxisomes
Or 2. Fe tightly bound to ferritin

Question 4

What are the two reactions that can generate Hydroxyl radicals spontaneously in the body?

Answer 4

1. Haber-Weiss Reaction

2. Fenton Reaction

Question 5

What are some methods to get rid of Hydrogen Peroxide?

Answer 5

1. Catalase
2. Glutathione Peroxidase with Glutathione Reductase
3. Iron (II) as reducing agent (Note: it makes hydroxyl radical)

Question 6

Oxygen tends to accept single electrons to form ___ ___ ___

Answer 6

Reactive Oxygen Species (ROS)

Question 7

Oxidative Stress causes ___ (what) to be greater than ___ (what)

Answer 7

ROS and RNOS production will be greater than ROS and RNOS removal/protection by cell defenses. This may cause damage in cell, etc.

Question 8

Name three repair mechanisms in the body against oxygen toxicity

Answer 8

1. DNA repair mechanism (slows down with age)
2. Removal of oxidized fatty acids from lipids
3. Oxidized proteins are degraded and replaced

Question 9

Name the sources of Reactive Oxygen Species (ROS) (6)

Answer 9

1. Ionizing Radiation
2. Various Drugs and Pollutants
3. Intermediates ‘escaping’ from the active sites of enzymes and respiratory chain
4. Oxidase reactions producing H2O2
5. Spontaneous Oxidation of hemoglobin
6. Respiratory Burst during Phagocytosis

Question 10

List the Three Major Reactive Oxygen Species (ROS)

and Two Major Reactive Nitrogen-Oxgen Species (RNOS)

Answer 10

ROS: Superoxide Anion (O2-), Hydrogen Peroxide (H2O2), Hydroxyl Radical (OH.)
RNOS: Nitric Oxide (NO), Peroxynitrite (ONOO-)

Question 11

Ischemia-Reperfusion Injury:

Some damage resulting from ischemic conditions may be a due to ___ ___ ___ during reperfusion with oxygen

Answer 11

Due to excessive ROS production

Question 12

Flavonoids are present in?

Answer 12

Green Tea
Red Wine
Chocolate

Question 13

Describe how ROS cause Cellular Damage through Protein Damage

Answer 13

ROS oxidizes amino acids in proteins which causes:

1. Fragmentation
2. Cross-linkage
3. Aggregation
4. Increased susceptibility to proteolytic digestion

Question 14

Describe how ROS cause Cellular Damage through membrane damage

Answer 14

ROS initiates chain reactions that cause Peroxidation of Lipids and make Lipid Free Radicals

This disrupts structural organization of membranes by causing degradation and makes aldehyde products that cross-link proteins

Question 15

Describe how ROS cause Cellular Damage through DNA Damage

Answer 15

ROS 1. breaks strands of DNA and 2. cause base alterations

Free radicals cause modification of up to 104 DNA bases/cell/day

Question 16

Definition: Respiratory Burst

Answer 16

Rapid consumption of Oxygen or Rapid release of reactive oxygen species by activated neutrophils in response to infectious agents and other stimuli.

Produces ROS and RNOS during phagocytosis

Question 17

Definition: Reactive Oxygen Species (ROS)

Answer 17

Highly reactive radicals dervied from oxygen

Question 18

Definition: Radical (Free Radical)

Answer 18

a reactive atom or group of atoms that contains one or more unpaired electrons

Question 19

Define what Free Radical Scavengers are and name Three species used for cellular defense against oxygen toxicity

Answer 19

Free Radical Scavengers are species in the cell that takes away reactive electrons from free radicals to protect the cell from ROS

1. Vitamin E
2. Vitamin C (ascorbic acid)
3. Beta-Carotene (uric acid)

Question 20

Define the role of Therapeutic Hypothermia

Answer 20

Reduces funcitonal deficits after cardiac arrest

Question 21

Define methods of cellular damage by reactive oxygen species

Answer 21

1. Membrane Damage
2. Oxidation of Amino Acids in Protein
3. Damage to DNA

Question 22

Define how ROS is related to Parkinson’s Disease

Answer 22

ROS and RNOS may play a role in neuronal degradation, resulting in
reduced production and release of dopamine

Question 23

Define function of Vitamin E in its role as Free Radical Scavenger

Answer 23

Vitamin E principally protects membranes against lipid peroxidation

Question 24

Define function of Vitamin C in its role as Free Radical Scavenger

Answer 24

The likely main role of Vitamin C is to regenerate the reduced form of Vitamin E

Question 25

Dark green leafy vegetable may be protective against Age-related macular degeneration because?

Answer 25

They contain lutein and zeaxanthin in high levels

Question 26

Clinical Significance of Macular Carotenoids is that it may…

Answer 26

Epidemiological studies suggest that the macular carotenoids may decrease the incidence and retard the progression of age-related macular degeneration

Question 27

Age-Related Macular Degeneration (AMD) causes?

Answer 27

Blindness in over 50-year-olds (in USA) due to exposure to high oxygen levels which cause high membrane content of unsaturated fatty acids

Question 28

Ischemia-reperfusion injury. Presence/Rise in ___ and ___ are implication through ROS production

Answer 28

Xanthine Oxidase and Inflammation

Question 29

Name the antioxidant enzymes (4) used for cellular defense against oxygen toxicity

Answer 29

Superoxide Dismutase
Catalase
Glutathione Peroxidase
Glutathione Reductase