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Flashcards in Week 5 ROS Deck (30):
1

what are ROS?

free radicals that have a single unpaired electron

2

what is the structure of super-oxide?

ROS: O2*- (*=lone electron)

3

what is the structure of hydroxyl radical?

OH*

4

where are superoxides produced?

mitochondria (Complex I+III of ETC), cytosol (XO), Lysosomes

5

What is the "lifespan" of a superoxide? key enzyme?

relatively short and they dont diffuse through membranes. they are quickly converted to H2O2 by superoxide dismutase

6

where is SOD located?

cytoplasm and mitochondria

7

H2O2 distribution within the cell

diffuses readily throughout the cell (also produced by auto oxidation in mito, oxidases in peroxisome, and SOD of mito and cyto)

8

what is the fenton reaction?

a reaction catalyzed by Cu and Fe that converts H2O2 to hydroxyl radicals

9

how else (other than fenton) can hydroxyl radicals be produced?

radiation + H2O

10

what is the roles (4) of peroxisomes?

beta oxidation of branched and VLCFA, AA catabolism, synthesis of bile acids (liver) and synthesis of plasmolegens (found in lipid membranes of brain, heart, neutrophils)

11

what enzymes do peroxisomes contain? what are their roles?

catalase and peroxidase and other oxidative enzymes: break down AA and FA

12

what is a by-product of FA oxidation in peroxisomes?

H2O2

13

what is the role of catalase located? 2

converts H2O2 to H2O. peroxisome and lysosome

14

NADPH oxidase: size, role, found?

5 enzyme complex found associated with the membrane of lysosomes within Phagocytes (macrophages, monocytes, neutrophils). catalyze the formation of superoxide and NADP from NADPH and O2

15

where does the superoxide produced by phagolysosomes reside?

within the phagolysosomes; essential for the degradation/lysis of engulfed material

16

what are the fates of superoxide within a lysosome? 3

1. converted to H2O2 via SOD
2. H2O2 can be converted to water via catalase
3. H2O2 can be converted to HOCl via myeloperoxidase

17

what is the role of HOCl within a phagolysosome

HOCl is toxic to bacteria

18

what is chronic ganulomatous disease (cause? symptoms?)

caused by more than 400 gene mutations in 1 of 5 NADPH oxidase enzymes. Symptoms include frequent life threatening bacterial and fungal infection due to a lack of HOCl production

19

what is the role of Xanthine oxidase? found?

produces H2O2 and superoxide within the cytoplasm of cells as by-products of uric acid synthesis

20

What is the treatment for gout?

XO inhibitors to decrease the amount of uric acid crystals in kidney and joints

21

what is oxidative stress?

imbalance of ROS; could be high ROS or low ROS

22

what are three macromolecular complications associated with high ROS

lipid peroxidation, protein fragmentation, DNA oxidation

23

what is the cause of lipid peroxidation

ROS produce chain rxn of lipid peroxide formation.

24

what is the issue with lipid peroxidation 4

structural changes in PM (increase permeability), crosslinks with DNA, direct toxicity, disrupt signaling

25

what is the cause of protein fragmentation? what does it result in 3

ROS attack Cys, Met, Pro, His, Arg of membrane and cystolic proteins. causes protein degradation, altered protein fxn and increase membrane permeability (cell swells)

26

what do ROS do to DNA, what does this result in? 3

cause base modifications, ss DNA breaks and cross-linking. results in DNA repair, cell death or cancer

27

what are pro-oxidants? what are some examples?

induce oxidative stress. Ex. Mg, Fe, Cu that catalyze the fenton rxn

28

how do antioxidants fxn?2

prevent the formation of ROS or compete with oxidizable substrates

29

what are some examples of preventative anti-oxidants

XO inhibitors, NADPH oxidase inhibitors, metal chelaters

30

what are some examples of anti-oxidants (4)

1. SOD
2. Catalase
3. Glutathione reductase system (H202-->H2O in mito and cyto)
4. Vitamins C, E, A

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