BIOLOGICAL ROLE OF OXYGEN

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BIOLOGICAL ROLE OF OXYGEN

• Carbohydrate metabolism for ATP Production
  (Mitochondria)
• Degradation of metabolic by-products by
  (Peroxisomes)

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CELLULAR RESPIRATION
Production of Reactive Oxygen Species
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REACTIVE OXYGEN SPECIES (ROS)
NADPH O2
NADPH oxidase
Superoxide (O2-.)
Superoxide dismutase
Hydrogen peroxide (H2O2)
Myeloperoxidase
Hypochlorite (HOCl)
Fe2
Catalase
Hydroxyl radical (OH.)
O2 H2O
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GENERATION OF REACTIVE OXYGEN SPECIES
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GENERATION OF ROS AS METABOLIC BY-PRODUCTS
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GENERATION OF ROS IN IMMUNE DEFENSES
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OXIDATIVE DAMAGES
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OXIDATIVE DAMAGE TO LIPIDS

• Increase membrane rigidity
• Reduce activity of membrane-bound enzyme
• Alter activity of membrane receptors
• Alter cell permeability

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OXIDATIVE DAMAGE TO PROTEINS

• Site-specific amino acid modifications
• Fragmentation of peptide chain
• Aggregation of cross-linked reaction products
• Increased susceptibility to proteolysis
• Degradation of enzymes

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OXIDATIVE DAMAGE TO NUCLEIC ACIDS

• Mutation
• Single strand breakage
• Nucleotide degradation
• Cross-linking to protein

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ANTIOXIDANTS
Enzymatic Antioxidants
Superoxide dismutase Catalysis the dismutation of superoxide to hydrogen peroxide.
Catalase Catalysis the dismutation of superoxide to water and oxygen.
Glutathione peroxidase Degradation of hydrogen peroxide
Non-Enzymatic Antioxidants
Vitamin E Trap peroxy radicals in cellular membranes.
Vitamin C Reduce radicals from a variety of sources. Recycling of Vitamin E radicals.
Glutathione Defense against reactive oxygen species.