TCA components

During periods of low plasma glucose e.g. during starvation or exercise, any of the following substrates may become available to the liver:

• fatty acids from lipolysis
• lactate from anaerobic glycolysis
• amino acids such as leucine and alanine

All can become incorporated into the tricarboxylic acid cycle to yield intermediate compounds. These intermediates limit glycolysis and so favour the reverse pathway of gluconeogenesis:

• increased citric acid concentration decreases the activity of 6-phosphofructokinase
• increased acetyl coenzyme A concentration decreases the activity of pyruvate dehydrogenase