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Foundations 1 > Week 5 ROS > Flashcards

Week 5 ROS Flashcards

1
Q

what are ROS?

A

free radicals that have a single unpaired electron

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2
Q

what is the structure of super-oxide?

A

ROS: O2- (=lone electron)

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3
Q

what is the structure of hydroxyl radical?

A

OH*

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4
Q

where are superoxides produced?

A

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

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5
Q

What is the “lifespan” of a superoxide? key enzyme?

A

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

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6
Q

where is SOD located?

A

cytoplasm and mitochondria

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7
Q

H2O2 distribution within the cell

A

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

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8
Q

what is the fenton reaction?

A

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

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9
Q

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

A

radiation + H2O

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10
Q

what is the roles (4) of peroxisomes?

A

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)

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11
Q

what enzymes do peroxisomes contain? what are their roles?

A

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

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12
Q

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

A

H2O2

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13
Q

what is the role of catalase located? 2

A

converts H2O2 to H2O. peroxisome and lysosome

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14
Q

NADPH oxidase: size, role, found?

A

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

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15
Q

where does the superoxide produced by phagolysosomes reside?

A

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

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16
Q

what are the fates of superoxide within a lysosome? 3

A
  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
Q

what is the role of HOCl within a phagolysosome

A

HOCl is toxic to bacteria

18
Q

what is chronic ganulomatous disease (cause? symptoms?)

A

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
Q

what is the role of Xanthine oxidase? found?

A

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

20
Q

What is the treatment for gout?

A

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

21
Q

what is oxidative stress?

A

imbalance of ROS; could be high ROS or low ROS

22
Q

what are three macromolecular complications associated with high ROS

A

lipid peroxidation, protein fragmentation, DNA oxidation

23
Q

what is the cause of lipid peroxidation

A

ROS produce chain rxn of lipid peroxide formation.

24
Q

what is the issue with lipid peroxidation 4

A

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

25
Q

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

A

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
Q

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

A

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

27
Q

what are pro-oxidants? what are some examples?

A

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

28
Q

how do antioxidants fxn?2

A

prevent the formation of ROS or compete with oxidizable substrates

29
Q

what are some examples of preventative anti-oxidants

A

XO inhibitors, NADPH oxidase inhibitors, metal chelaters

30
Q

what are some examples of anti-oxidants (4)

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

Foundations 1 (65 decks)

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