Gluconeogenesis

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Gluconeogenesis is the production of glucose mostly from lactate, which is the end product of glycolysis. Other precursors molecules such as glycerol and amino acids, are repsectively derived from fat and protein catabolism[1]

The primary site of gluconeogenesis is located in the liver. It is, therefore, responsible for glucose homeostasis by transporting glucose throughout the systems via the bloodstream.
Essentially, gluconeogenesis (glucose synthesis) in a sense may seem to be the reverse reaction of glycolysis (glucose breakdown). However, these two reactions are not completely irreversible, due to the "one-way only" steps that are present in the individual biochemical processes, as well as the different catalysing enzymes involved.  

The three main enzymes of gluconeogenesis are pyruvate carboxylase, phosphoenol-pyruvate carboxykinase and fructose 1, 6-biphosphatase.  The first step is the conversion of pyruvate into oxaloacetate.
These three steps are all regulated by allosteric control and they are energy-consuming. Gluconeogenesis is inhibited by AMP and ADP. When the body is in low energy level, pyruvate is required to be transported into CAC to obtain energy. Since pyruvate is required for the synthesis of glycogen, low levels of pyruvate therefore give a negative feedback to the process of gluconeogenesis.

Furthermore, hormones also play an important role in gluconeogenesis, for instance insulin has an effect of inhibiting gluconeogenesis, on the other hand, presence of glucagon favours the process of glycogenolysisAdrenaline, however, promotes gluconeogenesis, as it provides a more usable energy source for the body for the "fight or flight" response[2].

References

  1. Berg J.M, Tymoczko J.L, Stryer L. Biochemistry, 7th edition, USA: W.H.Freeman and Company, 2012
  2. Berg J.M, Tymoczko J.L, Stryer L. Biochemistry, 7th edition, USA: W.H.Freeman and Company, 2012

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