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Energy systems in muscle cellsLactate metabolism

During exercise when muscles do not get enough oxygen, lactate is produced. After exercise oxygen dept must be repaid. Slow-twitch muscles rely on aerobic respiration. Fast-twitch fibres generate ATP through glycolysis only.

Part of Human BiologyHuman Cells

Lactate metabolism

is the breakdown of glucose into two molecules. During glycolysis, NADH is produced when hydrogen ions are passed to the coenzyme NAD.

When oxygen is available (aerobic conditions), pyruvate molecules progress into the citric acid cycle.

Anaerobic conditions

During vigorous exercise, oxygen is not available (anaerobic conditions) and pyruvate undergoes fermentation in the of the cell.

Hydrogen ions are transferred from the NADH to pyruvate. This produces lactate.

The removal of hydrogen ions from NADH regenerates NAD. NAD is needed to maintain ATP production through glycolysis

A flowchart showing the steps of lactate fermentation: glucose; pyruvate, lactate

In aerobic conditions, most ATP is produced in the electron transport phase. Electron transport is not supported in lactate metabolism, so this results in much less being produced than in aerobic respiration.