Production of lactate in animals

• Anaerobic respiration leading to the production of lactate occurs in animals as a means of overcoming a temporary shortage of oxygen. This can be used as a survival advantage.
• Lactate production occurs most commonly in muscles as a result of strenuous exercise. In these conditions oxygen may be used up more rapidly than it can be supplied, creating an oxygen debt.
• When oxygen is in short supply, NAD from glycolysis can accumulate and must be removed. To achieve this, each pyruvate molecule produced takes up the two hydrogen atoms from the reduced NAD produced in glycolysis to form lactate.
• The summary equation for anaerobic respiration in animals is: pyruvate + reduced NAD -> lactate + oxidised NAD.
• At some point, the lactate produced is oxidised back to pyruvate. This can then either be further oxidised to release energy or converted into glycogen. This occurs once oxygen is available again.
• Lactate will create cramp and muscle fatigue if it is able to accumulate in the muscle tissue.
• As lactate is an acid, it also causes certain changes which affect enzymes.
• Although muscle has a certain tolerance to lactate, it is still vital that it is removed by the blood and taken to the liver to be converted to glycogen.