Micronutrients (Oxidant Defense) Flashcards
How are Reactive Oxygen Species (ROS) produced?
- by-product of ETC when proper electron flow fails - “leakage”
Which is a more reactive ROS: H2O2 or OH*?
OH*
What are the two fates of H2O2?
- Glutathione peroxidase converts it to 2H2O
- H2O2 reacts with an electron and produces OH*
What are the vitamin E vitamers?
- 4 tocopherols (alpha, beta, gamma, delta)
- 4 tocotrienols (alpha, beta, gamma, delta)
Which Vitamin E vitamer has significant activity in the body?
a-tocopherol
Where is Vitamin E found?
naturally in foods
What is the major difference between tocopherols and tocotrienols?
- tocopherols have a saturated side chain
- tocotrienols have an unsaturated side chain
RRR-a-tocopherol binds to:
Tocopherol Transfer Protein (TTP)
What is the fate of Vitamin E in its metabolism?
- 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
Where does selenium come from?
- Plants
- plants incorporate selenium from soil into met and cys
How do selenoAA travel in the blood?
freely
What version of selenium does the body use?
selenocysteine
What is glutathione’s (GSH) function?
- 2GSH donates 2 electrons to a PUFA hydroperoxide to convert it to safer 2H2O
- GSH becomes reduced to GSSG
What are the two important selenoproteins involved in oxidant defense?
- Glutathione peroxidase
- Fatty acid peroxidase
Does a healthy cell have more GSH or GSSG?
GSH
Vitamin C is also known as ____ at physiological pH
ascorbate
Vit. C exists in both D and L isomers, which ones are biologically active in humans?
L
Can humans synthesize Vit. C from glucose?
No, but many mammals can (except humans, primates, fruit bats, guinea pigs some birds) because they have the enzyme gluconolactone oxidase
How is vitamin C digested and absorbed?
- doesn’t have to be digested prior to absorption
- uptake via sodium-dependent vitamin C 1 and 2 transporters (SVCT)
How is vitamin C found in the circulation?
freely
What are the two biologically active forms of Vit. C? Are they oxidized or reduced? What form is primarily found in food?
- ascorbic acid (reduced) - found in food
- dehydroascorbic acid (oxidized) - found in small amounts in food
What biological processes is vit. C found in?
- collagen synthesis
- tyrosine synthesis
- neurotransmitter synthesis
What is the role of vit. C in collagen synthesis
donate an electron to form proline-OH (regeneration of prolyl hydroxylase-Fe2+)
What is scurvy caused by?
Vit. C deficiency
