Krebs Cycle Wikipedia

The citric acid cycle (also known as the Krebs cycle, or tricarboxylic acid (TCA) cycle) has already been discussed in detail on steemit. The article by @simplifylife (Powerhouse of the cell, Episode 5 : Krebs cycle, The missing link!!) is particularly informative, and emphasizes the critical importance of this pathway in human biology and biochemistry. The mammalian citric acid cycle is extensively discussed in many textbooks (see for example: 'Biochemistry', by C.K. Mathews and K.E. van Holde. The Benjamin/Cummings Publishing Company, Inc. (1990); 'Biochemistry 2nd Edition', by L. Stryer. W.H. Freeman and Company. (1981); 'Biochemistry, 5th Edition', by J.M. Berg, J.L. Tymoczko and L. Stryer. W.H. Freeman and Company. (2002)). Excellent web resources are also available that discuss the mammalian pathway (and its tight coupling with mitochondrial respiratory electron transport and oxidative phosphorylation) in great detail:

Citric acid cycle - Wikipedia

Cellular respiration - Wikipedia

Oxidative phosphorylation - Wikipedia

Mitochondrion - Wikipedia

but few of these resources point out some fundamental differences between the mammalian and plant pathways!

Here I would like to point out some unique features of the plant citric acid cycle, and highlight its flexibility.

As background reference material on the plant citric acid cycle I

in the synthesis of aspartate or glutamate, respectively), it is necessary to replenish the cycle to prevent depletion of intermediates. This replenishment is accomplished in mammals and many bacteria, by pyruvate carboxylase (an enzyme that combines pyruvate and bicarbonate (at the expense of ATP) to form oxaloacetate. Here's the first difference between animals and plants. In plants this anaplerotic synthesis of oxaloacetate to replenish the cycle is accomplished with phosphoenolpyruvate (PEP) carboxylase rather than pyruvate