The oxidation of acetyl-CoA of TCA cycle produces energy, CO2, and water.

Aspartate, which is formed from oxaloacetate through transamination reaction, is used for the synthesis of argininosuccinate and purines. The final product of this process is fumarate, which enters the TCA cycle.

Acetyl-CoA and glycerol are needed for the synthesis of steroids and fatty acids. For porphyrin synthesis, succinyl-CoA and glycerol are required as precursors. TCA cycle is thus involved in synthesis of haemoglobin, cytochromes and haemoproteins.

Amino Acid Metabolism A number of glycogenic amino acids enters the TCA cycle via transamination reactions.   Glutamate  α-KetoglutarateAspartate  OxaloacetateAlanine  Pyruvate

The word ‘amphi’ means both—the anabolic and catabolic reactions occur in the same pathway or cycle and hence TCA cycle is regarded as ‘amphibolic’.

TCA cycle is called amphibolic pathway as explained in Figure 8.8 because both catabolic and anabolic processes are involved in this pathway. Figure 8.8 Tricarboxylic Acid Cycle or Citric Acid Cycle Catabolic process: The cycle helps in the degradation of acetyl residues, which are derived from carbohydrates, fats, proteins, and so on. Anabolic process: The intermediates of TCA cycle are…

Tricarboxylic acid (TCA) cycle takes place in most of the tissues, but liver is the only tissue where it occurs to a significant extent. The enzymes of the citric acid cycle are located in the mitochondrial matrix, either free or attached to the inner mitochondrial membrane and the crista membrane, where the enzymes of the…

INTRODUCTION The citric acid cycle, Krebs cycle, or tricarboxylic acid cycle is the pathway that occurs in mitochondria that oxidises acetyl-CoA and reduces the coenzymes NADH+ and FADH2 reoxidised through the electron transport chain. The third phase of metabolism is the citric acid cycle. The carbohydrate, lipid and protein finally meet in this pathway, because glucose, fatty…

PFK-1 catalysed step is the irreversible step that commits a cell to convert glucose to glycolysis. Apart from the substrate-binding sites, this enzyme contains additional sites (regulatory sites) where allosteric activators or inhibitors bind. ATP not only serves as a substrate for PFK-1 but it also becomes the end product of the glycolytic pathway. When…

Carbohydrate metabolism provides the precursors for biosynthetic process and also produces ATP. It is very important for a cell to maintain the concentration of ATP at a nearly constant level. The regulation of glycolysis is carried by an enzyme-linked rate-limiting step. The rate-limiting step for this pathway is an irreversible reaction, and hence, the rate…