Micronutrients (Oxidant Defense)

Question 1

How are Reactive Oxygen Species (ROS) produced?

Answer 1

• by-product of ETC when proper electron flow fails - “leakage”

Question 2

Which is a more reactive ROS: H2O2 or OH*?

Answer 2

OH*

Question 3

What are the two fates of H2O2?

Answer 3

1. Glutathione peroxidase converts it to 2H2O
2. H2O2 reacts with an electron and produces OH*

Question 4

What are the vitamin E vitamers?

Answer 4

• 4 tocopherols (alpha, beta, gamma, delta)
• 4 tocotrienols (alpha, beta, gamma, delta)

Question 5

Which Vitamin E vitamer has significant activity in the body?

Answer 5

a-tocopherol

Question 6

Where is Vitamin E found?

Answer 6

naturally in foods

Question 7

What is the major difference between tocopherols and tocotrienols?

Answer 7

• tocopherols have a saturated side chain
• tocotrienols have an unsaturated side chain

Question 8

RRR-a-tocopherol binds to:

Answer 8

Tocopherol Transfer Protein (TTP)

Question 9

What is the fate of Vitamin E in its metabolism?

Answer 9

• Donates an electron to a PUFA peroxyradical to make it a less reactive hydroperoxide
• Become Vit. E radical
• Excreted in urine as quinone OR excreted in bile as a vit. E dimer

Question 10

Where does selenium come from?

Answer 10

• Plants
• plants incorporate selenium from soil into met and cys

Question 11

How do selenoAA travel in the blood?

Answer 11

freely

Question 12

What version of selenium does the body use?

Answer 12

selenocysteine

Question 13

What is glutathione’s (GSH) function?

Answer 13

• 2GSH donates 2 electrons to a PUFA hydroperoxide to convert it to safer 2H2O
• GSH becomes reduced to GSSG

Question 14

What are the two important selenoproteins involved in oxidant defense?

Answer 14

• Glutathione peroxidase
• Fatty acid peroxidase

Question 15

Does a healthy cell have more GSH or GSSG?

Answer 15

GSH

Question 16

Vitamin C is also known as ____ at physiological pH

Answer 16

ascorbate

Question 17

Vit. C exists in both D and L isomers, which ones are biologically active in humans?

Answer 17

L

Question 18

Can humans synthesize Vit. C from glucose?

Answer 18

No, but many mammals can (except humans, primates, fruit bats, guinea pigs some birds) because they have the enzyme gluconolactone oxidase

Question 19

How is vitamin C digested and absorbed?

Answer 19

• doesn’t have to be digested prior to absorption
• uptake via sodium-dependent vitamin C 1 and 2 transporters (SVCT)

Question 20

How is vitamin C found in the circulation?

Answer 20

freely

Question 21

What are the two biologically active forms of Vit. C? Are they oxidized or reduced? What form is primarily found in food?

Answer 21

• ascorbic acid (reduced) - found in food
• dehydroascorbic acid (oxidized) - found in small amounts in food

Question 22

What biological processes is vit. C found in?

Answer 22

• collagen synthesis
• tyrosine synthesis
• neurotransmitter synthesis

Question 23

What is the role of vit. C in collagen synthesis

Answer 23

donate an electron to form proline-OH (regeneration of prolyl hydroxylase-Fe2+)

Question 24

What is scurvy caused by?

Answer 24

Vit. C deficiency