Biochemistry Online: An Approach Based on Chemical Logic

Biochemistry Online





Learning Goals/Objectives for Chapter 8A:  After class and this reading, students will be able to

  • explain why oxidation reactions with ground state dioxygen have a high enough activation energy to make the reactions, although thermodynamically favored, kinetically slow
  • explain, using molecular orbital diagrams the difference between triplet and singlet dioxygen
  • using molecular orbital diagrams and Lewis structures, describe the chemical properties of the reduction products of dioxygen (superoxide, peroxide, and water)
  • explain the ways that biological systems use to enhance dioxygen activity and reduce the effects of reactive oxygen species (ROS) such as superoxide and peroxide
  •  write chemical reactions and mechanisms when appropriate for some reactions of triplet and singlet dioxygen, superoxide, peroxide and the hydroxy free radical
  • describe typical reaction of ROS with lipids, proteins, and nucleic acids and data to support the involvement of ROS in complex diseases and aging.
  • Briefly contrast the production and biological activities of ROS and reactive nitrogen intermediates (RNIs)

A9.  Antioxidant and Disease

If oxidative damage by dioxygen reduction products can cause disease, maybe antioxidant vitamins (E, C, A), which can form reasonably stable free radical, can protect the body from their effects.

Figure:  antioxidant vitamins (E, C, A)

It has been shown that these vitamins can help protect white blood cells from DNA damage arising from hydroxy free radicals. Vitamin E, a fat-soluble vitamin carried in circulating lipoproteins, can reduce the risk of cardiovascular disease, presumably by preventing oxidation of lipids and proteins in lipoproteins. Vitamin E and C, along with a common food additive, butylated hydroxytoluene (BHT) can form stable free radicals (formed possibly by abstraction of a hydrogen atom by hydroxyl free radicals) since the lone electron is stabilized by resonance and the the O-centered resonant form is sterically restricted from intermolecular interactions which could propagate the free radical chain reactions.

TBA:  Recent literature showing link to antioxidants and cancer

Human mitochondrial protein database from the NIST


Return to Chapter 8A:  The Chemistry of Dioxygen Sections

Return to Biochemistry Online Table of Contents

Archived version of full Chapter 8A:  The Chemistry of Dioxygen


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Biochemistry Online by Henry Jakubowski is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.