NAD⁺ (nicotinamide adenine dinucleotide) is a crucial coenzyme in glycolysis, acting as an electron carrier. It plays a fundamental role in energy production by accepting electrons released during glucose oxidation. This process reduces NAD⁺ to NADH.

Redox Reactions in Glycolysis

Glycolysis involves redox reactions where one molecule is oxidized (loses electrons) and another is reduced (gains electrons). NAD⁺ participates by accepting electrons from glycolytic intermediates, facilitating energy extraction from glucose. During glycolysis, specifically in the oxidation of glyceraldehyde 3-phosphate, NAD⁺ is reduced to NADH. This step is essential for harvesting energy from glucose.

Regeneration of NAD⁺

Since NAD⁺ is available in limited amounts within the cell, NADH must be converted back to NAD⁺ to sustain glycolysis:

• Aerobic Conditions: NADH donates electrons to the electron transport chain, regenerating NAD⁺ and allowing continuous glycolysis.
• Anaerobic Conditions: When oxygen is scarce (e.g., during intense exercise), NADH is oxidized back to NAD⁺ via lactate production, enabling glycolysis to proceed.

Role in ATP Production

NADH carries electrons to the mitochondrial electron transport chain, where oxidative phosphorylation generates ATP. Each NADH molecule contributes to ATP synthesis, increasing the efficiency of cellular energy production.

Net Production

Glycolysis results in a net production of two NADH molecules per glucose molecule. NAD⁺ exists in its oxidized form, while NADH is the reduced form, essential for maintaining cellular metabolism and energy balance.