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22 Cards in this Set

  • Front
  • Back
Advantages of O2
final acceptor in the ETC.
can oxidize other fatty acids and fuel molecules.
Disadvantages of O2
forms reactive O2 species.
Damage done by the O2 radical species
depolymerize polysaccarides involved in storage.
deconstruct the membrane by breaking double bonds.
denatures and inactives the enzymes.
damages DNA by disrupting the phosphate backbone.
Oxidative Stress
the antioxidants are overwhelmed and radicals can not be delt with.
4 types of reactive O2 species.
1. superoxide radical - precusor, O2 reacts with electron.
2. H2O2 - less reactive of the 4.
forms when O2.- reacts with H+ to form singlet and hydrogen peroxide.
3. Hydroxide radical- very reactive but short lived.
H2O2 reacts with iron. Iron is oxidized to Fe(III).
4. singlet O - very reactive because one electron moves up an orbital and when fall doawn it releases energy.
made same as H2O2 or preoxide goes to alcohol and singlet O2.
Ways to generate ROS in body.
in ETC - can donate an electron to O2 to generate superoxide radical.
fatty acid desaturation - transfer electron to O2.
uv light
resiratory bursts- happens in macrophages, used to get rid of bacteria or foreign substance.
In the lysosome NADPH oxidase converts O2 to superoxide radical and oxidizes NADPH.
Defenses against Oxidative Stress.
convert ROS to something less toxic.
prevent formation of hydroxide radical and singlet.
Superoxide Dismutase:
SOD - converts the superoxide to H2O2.
There are 2 SOD - SOD1 is in teh cytosol and SOD2 is in the mitochondria.
converts 2 H2O2 to 2H2O and O2.
catalase is a heme contain enzyme.
takes peroxide and turns it into water and O2.
selenium containing enzyme.
reduces H2O2 to water while oxidizing GHS to GSSH (makes disulfide bond between 2 glutathione) The reductase reduces GSSH back to 2 GSH while oxidizing NADPH to NADP+
Reductase and peroxiredoxins work together in a cycle to do what?
to reduce H2O2 to water.

the reductase reduces GSSH to 2GSH.
4 antioxidant enzymes
2 antioxidant molecules:
thiol antioxidants
phenolic antioxidant
Vitamen C
thiol antioxidant molecules
responsible for forming disulfide bonds.
EX: lipoic acid
glutathion (GSH)
Phenolic antioxidants
contain a phenol, the double bonds can stablize the radical. Lots of radical resonance structures.
EX: vit. E and CoQ
made of isoprenoid units and contains double bonds.
Vit. C
reversibly oxidized. it acts to oxidize other antioxidants expecially vit. E.
Malaria is caused by several species of plasmodium.
Mosquito transfers a sporoite into the blood, teh parasite proliferates in liver producing merozoites.

Merozoites invade RBC and feeds on Hb.
Mech. that malarial parasite has to protect itself from ROS.
merozoites convert heme to make a polymer called hemozoin.
FeII to FeIII to hemozoin.

SOD and catalyse converts ROS to less reactive species.

The GSH and thioreducine system protects by converting to H2O2.

Pentose Phosphate Pathway is only way to make NADPH that converts O2 to superoxide.
Resistance to Malaria.
if you have a defect enzyme G-6-P dehydrogenase then don't make G-6-P and cant enter the pentose pathway to you don;t get NADPH and dont make sureroxide radicals.
Antimalaria Drug
Chloroquine - inhibits product of hemozoin. So have more heme that makes the hydoxide radical and harms the parasite.

Artemesinin - forms carbon centered free radical the enteracts with Fe. Has an epoxide ring.

The drug breaks the epoxide ring and forms a oxide radical.