Nutrients, Oxidants, Antioxidants (Jenney)

Question 1

How are highly reactive oxygen radicals formed from O2?

Answer 1

When O2 accepts single electrons.

Question 2

What are radicals?

Answer 2

Compounds that contain a single electron, usually at an outside orbital.

Question 3

When does oxidative stress occur?

Answer 3

When the rate of ROS generation exceeds the capacity of the cell for their removal.

Question 4

What is oxidative stress?

Answer 4

Increase in ROS levels that may result in significant damage to cell structures.

Question 5

What is an oxidant?

Answer 5

Substance that is reduced and that, therefore, oxidizes the other component of an oxidation-reduction system.

Question 6

What does an antioxidant do?

Answer 6

Stops propagation of free-radical damage in membranes.

Question 7

Define ROS.

Answer 7

Chemically reactive molecules containing oxygen that are formed as a natural byproduct of the normal metabolism of oxygen.

Question 8

What are some examples of ROS?

Answer 8

Superoxide (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH-dot)

Question 9

Define RNS.

Answer 9

Family of antimicrobial molecules derived from nitric oxide and superoxide.

Question 10

What are some examples of RNS?

Answer 10

Nitric oxide (NO), peroxynitrate (ONOO-)

Question 11

What do reactive species do?

Answer 11

Directly damage DNA, RNA, proteins, sugars, lipids - everything!

Question 12

Are they made purposefully or accidentally?

Answer 12

Both: purposefully by immune system, accidentally via many reactions in ETC in RBCs.

Question 13

In what kind of reactions does iron act as an enzyme?

Answer 13

Catalysis, electron transfer, O2 transport

Question 14

How is iron stored in the body?

Answer 14

In ferritin and hemosiderin - mostly in the liver.

Question 15

Why are iron levels strictly regulated in the body?

Answer 15

To maintain a constant store.

Question 16

Explain iron uptake via transferrin.

Answer 16

Target cells contain specific receptors. Tf-receptor complex is internalized by receptor-mediated endocytocis. Fe is released by acidification. Transferrin and receptor are recycled by exocytosis.

Question 17

What substances inhibit non-heme uptake of iron?

Answer 17

Phytate & polyphenols in foods such as black tea and cocoa.

Question 18

What substances stimulate uptake of iron?

Answer 18

Vitamin C (ascorbic acid), organic acids, heme

Question 19

What is a hereditary defect that leads to iron excess?

Answer 19

Hemochromatosis

Question 20

What is a diet-influenced condition that leads to iron excess (does have a genetic component)?

Answer 20

Hemosiderosis - excess alcohol consumption (especially red wine), excess iron supplementation by children

Question 21

What are some causes of iron deficiency?

Answer 21

Anemia, infection (H. pylori - ulcers), vitamin deficiencies, inflammation

Question 22

Is vitamin E lipid or water soluble?

Answer 22

Lipid, but does not accumulate in liver to toxic levels

Question 23

Which vitamin can be found in vegetable oils, nuts, fish, and leafy green vegetables?

Answer 23

Vitamin E

Question 24

If a patient comes in with a problem of fat malabsorption, which vitamin does he have low levels of?

Answer 24

Vitamin E

Question 25

What is the main function of vitamin E?

Answer 25

Antioxidant - stop propagation of free-radical damage in membranes.

Question 26

Is vitamin E deficiency common?

Answer 26

Not from diet, but rare genetic abnormalities or fat malabsorption maladies may cause it.

Question 27

What are symptoms of vitamin E deficiency?

Answer 27

Pigmentosa, neurological symptoms (rate depends on level of ROS), may take years to develop if result from surgery or acquired fat malabsorption.

Question 28

What vitamin can regenerate reduced vitamin E?

Answer 28

Vitamin C

Question 29

Is vitamin C lipid or water soluble?

Answer 29

Water soluble

Question 30

What are its reversibly oxidized and reduced forms?

Answer 30

Ascorbic acid & dehydroascorbic acid

Question 31

How can vitamin C be regenerated?

Answer 31

By a number of different enzymes using electrons from NAD(P)H or glutathione.

Question 32

What is the first thing oxidized by plasma when under oxidative stress?

Answer 32

Vitamin C

Question 33

What happens when you have vitamin C deficiency?

Answer 33

Scurvy! Collagen needs vitamin C for proper development. Without it connective tissue in muscle, skin, and blood vessels is defective, leading to hemorrhagia, bleeding gums, weakness, and poor wound and bone healing. 10mg/day vitamin C can prevent this.

Question 34

Vitamin C acts as a cofactor to how many enzymes?

Answer 34

At least 8 different enzymes

Question 35

What happens when you consume megadoses of vitamin C?

Answer 35

Hypoglycemia, kidney stones, indigestion. Chewable supplements can dissolve tooth enamel. No direct evidence that megadoses cure colds or the flu.

Question 36

What is the 2nd thing oxidized in stressed plasma?

Answer 36

Bilirubin - bound to albumin, along with uric acid

Question 37

What is glutathione?

Answer 37

A small tripeptide that is reversibly oxidized/reduced. Good source of electrons to reduce ROS.

Question 38

Is there any evidence that vitamin C or E supplements help fight disease?

Answer 38

2 separate studies out of many have these positive results: 1 - higher plasma vitamin C levels, and, to a lesser degree, fruit and vegetable intake were associated with a substantially decreased risk of diabetes. 2- daily multivitamin supplementation modestly but significantly reduced the risk of total cancer.

Question 39

What is the proposed mechanism for tumoricidal actions of pharmacological ascorbate?

Answer 39

Ascorbate distributes from the blood to the tumor ECF compartments after IV administration. In tumor interstitium, ascorbate is oxidized to ascorbate radical by a metalloprotein catalyst that ultimately forms tumoricidal effector H2O2. Pharmacologic ascorbate concentrations in plasma resulted in formation of both ascorbate radical and H2O2 in ECF - excess ascorbate can act as an oxidant in SOME tumore cells, but only in pharmacologic doses.