Summary
Pyruvate is converted to lactate when oxygen is lacking, regenerating NAD+ for glycolysis.
In depth
Lactate dehydrogenase converts pyruvate to lactate, oxidising NADH to NAD+. Muscles produce lactate during heavy exercise; it travels to the liver (Cori cycle) or is used as a fuel by the heart. Soreness is not caused directly by lactate.
Lactic acid is converted back to pyruvate when oxygen is available. Its production allows glycolysis to continue so ATP flows.
Key idea: fermentation is about regenerating NAD+, not about making acid.
When oxygen is short, as in vigorously working muscle, pyruvate from glycolysis is reduced by lactate dehydrogenase to lactate, oxidising NADH to NAD+. This regenerates the NAD+ glycolysis needs, so it can continue making 2 ATP per glucose.
Lactate moves into the blood and is taken to the liver, where it is converted to glucose (Cori cycle) or used by heart and other muscle as fuel; muscle burn is caused by other factors as well as lactate. Some bacteria use lactic fermentation to make yoghurt, cheese and sauerkraut.
Example: Lactobacillus acidifies milk, curdling it.
Key idea: fermentation is not for making energy but for regenerating NAD+.
Frequently asked questions
What is Lactic Acid Fermentation?
Pyruvate is converted to lactate when oxygen is lacking, regenerating NAD+ for glycolysis.
Which area of biology covers Lactic Acid Fermentation, and how advanced is it?
Lactic Acid Fermentation is one of the 53 topics in Metabolism & Bioenergetics. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Cori Cycle, Oxygen Debt and Recovery, Alcoholic Fermentation.
Can you give an example of Lactic Acid Fermentation?
Lactic acid bacteria make yoghurt.
What should I learn before Lactic Acid Fermentation?
Lactic Acid Fermentation is a Beginner topic, so no earlier topic is required. Other Beginner topics in Metabolism & Bioenergetics that pair well with it include Metabolism, Anabolism and Catabolism, ATP.
What topics are related to Lactic Acid Fermentation?
The closest topics to Lactic Acid Fermentation are Cori Cycle, Oxygen Debt and Recovery, Alcoholic Fermentation, Aerobic and Anaerobic Respiration. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Lactic Acid Fermentation?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Lactic Acid Fermentation. To practise the whole of Metabolism & Bioenergetics, use the Metabolism & Bioenergetics quiz.
How is Lactic Acid Fermentation different from Cori Cycle?
Lactic Acid Fermentation: Pyruvate is converted to lactate when oxygen is lacking, regenerating NAD+ for glycolysis. Cori Cycle: Lactate from muscle is converted to glucose in the liver and returned, costing net ATP. Read both side by side and note what each one explains.
How should I study Lactic Acid Fermentation step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Cori Cycle and explain the difference aloud. Finally, take the Metabolism & Bioenergetics quiz and come back to this page for any question you miss.