reactive oxygen species (17) Flashcards
what is considered to the possible benefit of reactive oxygen species?
function as signals to promote cell proliferation and survival
what is the definition of reactive oxygen species? free radicals?
describes chemically reactive molecular species formed upon incomplete reduction of oxygen
-Those containing an unpaired electron are called free radicals
how is superoxide formed?
molecular oxygen is reduced to superoxide by a 1 electron reduction
how is hydrogen peroxide formed?
by reduction of superoxide
true or false
hydrogen peroxide is a free radical
false
hydrogen peroxide is not itself a free radical, but an oxidant that can generate other more reactive oxidants (such as hydroxyl radical)
in most cells, where is superoxide produced and why?
in the mitochondrial as a byproduct of ATP synthesis
list five times that O2- production is increased
- high membrane potential
- high NADH/NAD+ ratio
- electron transport damage
- hypoxia
- zenobiotics
where is NADPH oxidase found?
enzyme involved in superoxide production
found in phagocytes and maybe also in cardiomyocytes
where is xanthine oxidase used?
in purine metabolism
when is monoamine oxidase used?
dopamine metabolism
what is the fenton reaction
Transfers an electron to H2O2 from a free metal ion (ex. Fe or Cu) to form OH
what is the primary reactive nitrogen/oxygen species?
nitric oxide (NO)
how is NO generated?
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
if NO is a mild radical, how come it is dangerous?
it can react with O2- to form peroxynitrite (ONOO-) a very reactive oxidant
what damage does lipid peroxidation cause?
lipid peroxidation introduces charged peroxide group in the acyl chain of phospholipids and causes membrane damage
what is protein carbonylation?
hydroxyl radicals directly oxidize amino acid side chains→ cause protein damage
what is the first step in superoxide degeneration in the cell’s enzymatic defense mechanisms? 2nd step?
- superoxide dismutatse converts superoxide to hydrogen peroxide
- hydrogen peroxide is converted into water by catalase, glutathione peroxidase and peroixdoxin pathways
what two elements does cytocolic SOD1 depend on?
Cu and Zinc
what element does mitochondrial SOD2 depend on?
Mn
what element does glutathione peroxidase (necessary for H2O2 to water) contain?
selenium
where in the cell is catalase located?
in the peroxisome
tell me about the disorder: acatalasia
what does this disease tell us about H2O2 degradation?
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
what are 2 in vivo synthesized antioxidants?
glutathione
coenzyme Q
what are some beneficial/necessary effects of H2O2 and NO?
H2O2 and NO may be considered secondary messengers that regulate: cell proliferation, differentiation, tissue repair, inflammation and insulin signaling
tell me about ROSs and their involvement in innate immunity
- 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
what is the hesitation with using antioxidant protection therapy in cancer patients?
Antioxidants can protect healthy people from cancer, but can promote the growth of pre-initiated tumor cells
tell me about the correlation between ROSs and food intake?
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
