Statement I : The NADH synthesised in glycolysis is transferred into the mitochondria and undergoes oxidative phosphorylation. '

Statement II : NADH is oxidised to NAD+ fastly in fermentation and slowly in aerobic respiration

Key Points

• Statement I is true: During glycolysis, Nicotinamide Adenine Dinucleotide, reduced form (NADH) is produced in the cytoplasm. Since the mitochondrial inner membrane is impermeable to NADH, the electrons from NADH are transferred to the electron transport chain in the mitochondria using shuttle systems, which subsequently undergo oxidative phosphorylation to produce ATP.
• NADH plays a key role in energy production: It donates electrons to the electron transport chain, which generates a proton gradient that drives ATP synthesis.
• Statement II is false: In fermentation, NADH is oxidized back to NAD+ quickly to sustain glycolysis in the absence of oxygen. However, in aerobic respiration, NADH oxidation via oxidative phosphorylation is a highly efficient process, producing much more ATP.
• Fermentation is less efficient: It regenerates NAD+ but produces significantly less ATP compared to oxidative phosphorylation in aerobic respiration.

Additional Information

• Aerobic Respiration: This process occurs in the presence of oxygen, where glucose is completely oxidized into carbon dioxide and water. It involves glycolysis, the Krebs cycle, and oxidative phosphorylation. It is highly efficient, producing approximately 36-38 ATP molecules per glucose molecule.
• Fermentation: In the absence of oxygen, cells rely on fermentation to regenerate NAD+ from NADH to sustain glycolysis. Two common types are lactic acid fermentation (in muscle cells) and alcoholic fermentation (in yeast). Only 2 ATP molecules are produced per glucose molecule.
• Shuttle Systems: The NADH produced during glycolysis cannot directly enter the mitochondria. Instead, shuttle systems like the glycerol-phosphate shuttle or the malate-aspartate shuttle transfer electrons from cytosolic NADH to mitochondrial carriers, facilitating its entry into oxidative phosphorylation.
• Oxidative Phosphorylation: This is the process by which ATP is synthesized using the energy released by the electron transport chain. It occurs in the inner mitochondrial membrane and utilizes oxygen as the final electron acceptor.
• NADH Function: NADH serves as an essential electron donor in metabolic reactions. It transfers high-energy electrons to the electron transport chain, aiding in the production of ATP.
• Comparison of Energy Efficiency: Aerobic respiration is far more efficient than fermentation. While aerobic respiration yields 36-38 ATP molecules per glucose molecule, fermentation yields only 2 ATP molecules.