Oxygen toxicity Flashcards
What is meant by reactive oxygen species?
Chemically reactive molecules containing oxygen
They are highly reactive
With unpaired electrons in outer shell
What is the difference between endogenous and exogenous reactive oxygen species?
Endogenous:
Natural by-product of O2 metabolism
Produced mostly inside cell organelles, for example mitochondria
Exogenous:
UV radiation, smoking, inflammation
What is O22• ?
Normal oxygen!
Name and desrcibe the reactive molecule species.
OH• (hydroxyl radical)
Most potent radical
Produced by H2O2 (Fenton’s)
O2•– (superoxide)
Produced by ETC
Generates other radicals locally
H2O2 (hydrogen peroxide)
Not a radical
Generates radicals with transition metals
Lipid soluble
What is Fenton’s reaction?
The iron dependent generation of a hydroxyl radical from H2O2
H2O2 + Fe+ > Fe3+ + OH• + OH-
What is the Haber-Weiss reaction?
A combination of two ionic equations - Fenton’s and superoxide to oxygen reaction
O2- + H2O2 > O2 + H2O + OH•
What is a benefit of reactive oxygen species?
Respiratory burst - immune system defence against bacteria
Describe respiratory burst.
Superoxide is released during phagocytosis
Superoxide generates other reactive oxygen species
This damages the cell membrane of bacteria
Give the methods of defence against oxygen toxicity the body has.
Antioxidant enzymes
Antioxidant vitamins
Cellular compartmentation
Repair
What are the problems the reactive oxygen species can cause?
Cellular damage
Damages membranes of cells: mitochondrial, RER and cell
Damage to membranes = influx of water, calcium and sodium = death
Name some antioxidant enzymes. What do they do?
Catalase
Superoxidase dismutase
Convert ROS into not ROS
Give some example of antioxidant vitamins.
Vitamin C
Vitamin E
Carotenoids
