Cellular Respiration: The Role of Reduced Coenzymes

Reduced Coenzymes and ATP Formation

• Primary products of the TCS pathway are reduced coenzymes FADH2 and NADH.
• NADH is also a product of glycolysis, produced in the cytosol, but mitochondria cannot import it directly.
• Instead, NADH enters mitochondria indirectly through malate-aspartate shuttle or glycerol phosphate shuttle.

Electron Transport Chain and ATP Synthesis

• High-energy electrons from FADH2 or NADH are passed to the electron-transport chain in the inner mitochondrial membrane.
• Electrons pass along the electron-transport chain, releasing energy through a series of reactions.
• Energy from these reactions is stored in the form of an electrochemical gradient of protons across the inner mitochondrial membrane.
• Eventually, low-energy electrons are transferred to molecular oxygen (O2), reducing it to water.

ATP Formation through Chemiosmosis

• Controlled movement of protons back across the membrane through an ATP-synthesizing enzyme provides energy for phosphorylating ADP to ATP
• This process occurs through the chemiosmotic mechanism

Electron Transport Chain and ATP Formation

• Each pair of electrons transferred from NADH to oxygen releases energy to form approximately 3 molecules of ATP
• Each pair of electrons donated by FADH2 releases energy to form approximately 2 molecules of ATP

ATP Yield from Glucose Catabolism

• One molecule of glucose, completely catabolized through glycolysis and the TCA cycle, yields a net gain of approximately 36 ATPs
• This includes the GTP formed by each round of the TCA cycle
• The actual number of ATPs formed per molecule of glucose oxidized depends on the cell's specific activities

Learn about the importance of coenzymes FADH2 and NADH in the formation of ATP during cellular respiration. This quiz covers the electron transport chain and the role of mitochondria in energy production.