Biological Oxidation and Energy Generation

Energy Generation in the Body

• Biological oxidation is crucial in energy generation within the body, playing a key functional role.
• The respiratory chain and ATP synthesis are integral parts of this process.
• The Citric Acid Cycle (CAC) is essential for energy production.

Stages of Energy Generation

• Stage 1: Acetyl-CoA production: Molecules like glucose, amino acids, and fatty acids are broken down to produce Acetyl-CoA.
• Stage 2: Acetyl-CoA oxidation: Acetyl-CoA enters the Citric Acid Cycle where it is oxidized.
• Stage 3: Electron transfer and oxidative phosphorylation: Electrons released during oxidation are transferred along the Electron Transport Chain to generate ATP, the body's primary energy currency.

Electron Transport Chain (ETC)

• Location: The ETC occurs in the inner mitochondrial membrane.
• Components: The ETC has four protein complexes (I, II, III, and IV) and two electron carriers (Coenzyme Q and cytochrome C).
• Mechanism: Electrons are passed along the chain, releasing energy that pumps protons (H+) from the mitochondrial matrix to the intermembrane space.
• Function: This proton gradient generates a driving force for ATP synthesis. Oxidized forms of coenzymes (NAD+ and FAD) are regenerated to continue the process. Energy is released through the electron transport.

Oxidative Phosphorylation

• Mechanism: This enzymatic process uses the electrochemical potential established by the proton gradient across the inner mitochondrial membrane to phosphorylate ADP and generate ATP from ADP + Pi.
• Role of ATP Synthase (Complex V): ATP synthase is the enzyme that catalyzes the formation of ATP from ADP and Pi using the proton gradient.

Chemiosmotic Theory

• Explanation: This theory explains how electron transport and oxidative phosphorylation are coupled through the creation of a proton gradient across the inner mitochondrial membrane. The energy stored in the form of this gradient is harnessed to generate ATP.
• Steps: The ETC pumps protons across the inner mitochondrial membrane generating a proton gradient. The protons then flow back into the mitochondrial matrix through ATP synthase generating ATP. This is a thermodynamically favorable process.
• Proton-motive Force: The combination of the chemical and electrical potential difference created by the proton gradient across the inner mitochondrial membrane.

Citric Acid Cycle (CAC)

• Location: The CAC occurs in the mitochondrial matrix.
• Function: The multi-step process oxidizes acetyl-CoA, releasing carbon dioxide (CO2) and generating energy-carrying molecules like NADH and FADH2.
• Co-factors: The CAC also produces GTP or ATP, depending on the cell.
• Anabolic Importance: Intermediates produced in the CAC are vital precursors for the biosynthesis of glucose, fatty acids, and amino acids.
• Regulation: The rate of the CAC is regulated by the availability of substrates and feedback inhibition by the end products