Bio Chemistry

BIOCHEMISTRY 3(2+1)

Lesson 31 : Biochemical energetics and biological oxidation

Superoxide Production

Even though cytochrome oxidase and other proteins that reduce oxygen have been designed not to release O2.- (superoxide anion), it still does happen.

Protonation of superoxide anion yields hydroperoxyl radical (HO2.), which can react with another molecule to produce H2O2.

Enzyme superoxide dismutase catalyzes this reaction

Recent findings have indicated that superoxide dismutase mutations can cause amyotrophic lateral sclerosis (Lou Gehrig’s disease), in which motor neurons in brain and spinal cord degenerate.

The hydrogen peroxide formed is scavenged by catalase:

Peroxidases catalyze an analogous reaction:

Electron Transport System

• Takes place in Mitochondria
• Converts Hydrogen (Electron) carrier molecules to ATP
• Requires oxygen to complete process
• Provides net gain of 32 ATPs from Electron carriers (NADH & FADH2)

ATP from Hydrogen (Electron) Carriers in Electron Transport System

• NADH Converts to 3 ATPs
• FADH2 Converts to 2 ATPs
• Electrons (Hydrogen) are added to oxygen to form water as end product
• Thus … oxygen is final Hydrogen acceptor molecule