Amphibolic aspects of the TCA cycle

At each turn of the TCA cycle, oxaloacetate is regenerated and can combine with another acetyl-CoA 

a-Ketoglutarate succinate -I- CO2. This reaction is involved in the hydroxylation of prolyl and lysyl residues of protocollagen, a step in the synthesis of collagen. 

Succinyl-CoA -1- glycine -aminolevulnic acid (ALA). AT.A is then utilized for the synthesis of heme. 

Succinyl-CoA - - acetoacetate acetoacetyl-CoA - -succinate. This reaction is important in the activation of acetoacetate (a ketone body) and hence for its utilization in extrahepatic tissues. 

Utilization of intermediates in these reactions leads to their depletion and hence to a slowdown of the cycle unless they are replenished by the replacement or anaplerotic reactions listed below  

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