reactive oxygen species (17)

Question 1

what is considered to the possible benefit of reactive oxygen species?

Answer 1

function as signals to promote cell proliferation and survival

Question 2

what is the definition of reactive oxygen species? free radicals?

Answer 2

describes chemically reactive molecular species formed upon incomplete reduction of oxygen
-Those containing an unpaired electron are called free radicals

Question 3

how is superoxide formed?

Answer 3

molecular oxygen is reduced to superoxide by a 1 electron reduction

Question 4

how is hydrogen peroxide formed?

Answer 4

by reduction of superoxide

Question 5

true or false

hydrogen peroxide is a free radical

Answer 5

false
hydrogen peroxide is not itself a free radical, but an oxidant that can generate other more reactive oxidants (such as hydroxyl radical)

Question 6

in most cells, where is superoxide produced and why?

Answer 6

in the mitochondrial as a byproduct of ATP synthesis

Question 7

list five times that O2- production is increased

Answer 7

• high membrane potential
• high NADH/NAD+ ratio
• electron transport damage
• hypoxia
• zenobiotics

Question 8

where is NADPH oxidase found?

Answer 8

enzyme involved in superoxide production

found in phagocytes and maybe also in cardiomyocytes

Question 9

where is xanthine oxidase used?

Answer 9

in purine metabolism

Question 10

when is monoamine oxidase used?

Answer 10

dopamine metabolism

Question 11

what is the fenton reaction

Answer 11

Transfers an electron to H2O2 from a free metal ion (ex. Fe or Cu) to form OH

Question 12

what is the primary reactive nitrogen/oxygen species?

Answer 12

nitric oxide (NO)

Question 13

how is NO generated?

Answer 13

NO is generated by specific nitric oxide synthase (NOS) which metabolizes arginine to citrulline with the formation of NO via a 5 electron oxidative reaction

Question 14

if NO is a mild radical, how come it is dangerous?

Answer 14

it can react with O2- to form peroxynitrite (ONOO-) a very reactive oxidant

Question 15

what damage does lipid peroxidation cause?

Answer 15

lipid peroxidation introduces charged peroxide group in the acyl chain of phospholipids and causes membrane damage

Question 16

what is protein carbonylation?

Answer 16

hydroxyl radicals directly oxidize amino acid side chains→ cause protein damage

Question 17

what is the first step in superoxide degeneration in the cell’s enzymatic defense mechanisms? 2nd step?

Answer 17

1. superoxide dismutatse converts superoxide to hydrogen peroxide
2. hydrogen peroxide is converted into water by catalase, glutathione peroxidase and peroixdoxin pathways

Question 18

what two elements does cytocolic SOD1 depend on?

Answer 18

Cu and Zinc

Question 19

what element does mitochondrial SOD2 depend on?

Answer 19

Mn

Question 20

what element does glutathione peroxidase (necessary for H2O2 to water) contain?

Answer 20

selenium

Question 21

where in the cell is catalase located?

Answer 21

in the peroxisome

Question 22

tell me about the disorder: acatalasia

what does this disease tell us about H2O2 degradation?

Answer 22

autosomal dominant disorder with very low levels of catalase- these ppl are usually fine which tells you the other two pathways for H2O2 degradation are prob more dominant

Question 23

what are 2 in vivo synthesized antioxidants?

Answer 23

glutathione

coenzyme Q

Question 24

what are some beneficial/necessary effects of H2O2 and NO?

Answer 24

H2O2 and NO may be considered secondary messengers that regulate: cell proliferation, differentiation, tissue repair, inflammation and insulin signaling

Question 25

tell me about ROSs and their involvement in innate immunity

Answer 25

• they function as potent antimicrobial agents
• they participate as redox signaling molecules that modulate transcription factors, which regulate expression of key cytokines and chemokines that further regulate the inflammatory response

Question 26

what is the hesitation with using antioxidant protection therapy in cancer patients?

Answer 26

Antioxidants can protect healthy people from cancer, but can promote the growth of pre-initiated tumor cells

Question 27

tell me about the correlation between ROSs and food intake?

Answer 27

o ROS act as a signal activating POMC neurons to release anorexigenic hormones and decreasing AgRP’s activity in secreting orexigenic hormones—which would ultimately reduce food intake