Pyruvate is Converted to Lactate to Regenerate NAD⁺ in Anaerobic Respiration
- Glycolysis requires NAD⁺ to continue, but cells have a limited supply.Without oxygen, the electron transport chain can't regenerate NAD⁺, so glycolysis would stop.
- To solve this, pyruvate acts as an electron acceptor, allowing NAD⁺ to be recycled.
- Think of glycolysis as a factory assembly line producing ATP.
- NAD acts like a conveyor belt, carrying electrons to keep the line moving.
- Without oxygen, the conveyor belt gets stuck unless lactate production steps in to clear the jam.
Lactic Acid Fermentation Converts Pyruvate to Lactate and Regenerates NAD⁺
- The enzyme lactate dehydrogenase catalyzes the conversion of pyruvate to lactate.
- NADH donates its electrons to pyruvate, oxidizing NADH back to NAD⁺.
- Reaction: Pyruvate + NADH + H⁺ → Lactate + NAD⁺
- This does not produce ATP directly—its sole purpose is to regenerate NAD⁺ so glycolysis can keep running.
Pyruvate + NADH + H⁺ → Lactate + NAD⁺
- This reaction has two important outcomes:
- NAD⁺ is regenerated, allowing glycolysis to continue and produce ATP.
- Lactate (lactic acid) is produced as a waste product.
Lactate Is a Temporary Solution To Keep ATP Production Going
- Lactate accumulates in muscles during intense exercise, causing a pH drop and muscle fatigue.
- Once oxygen is available, lactate is converted back to pyruvate or transported to the liver for glucose synthesis.
Anaerobic respiration only yields 2 ATP per glucose (from glycolysis alone), far less efficient than aerobic respiration's 30+ ATP.
Theory of Knowledge- How does the concept of "oxygen debt" during intense exercise relate to the broader idea of resource management in biology and beyond?
- Can you think of other systems where temporary solutions are used to address immediate needs?
- Why is the regeneration of NAD essential for glycolysis to continue?
- What happens to lactate after anaerobic respiration?
