What does an Amphibolic pathway means?
Definition
of Amphibolic pathway:
An Amphibolic
pathway is a biochemical pathway that includes both anabolic and catabolic
processes
(Amphi
means both)
Anabolism
is the synthesis of complex molecules from simpler ones with input of energy. Catabolism
is the breakdown of complex molecules into simpler ones with the release of
energy
Examples
of Amphibolic pathway : Glycolysis, Krebs cycle, Pentose phosphate
pathway, Gluconeogenesis
These
pathways play an important role in cellular metabolism as it can shift between
anabolic and metabolic reactions depending on the requirement of the cell
The
Citric acid cycle is amphibolic; i.e., it serves as a catabolic and an anabolic
pathway.
The catabolic part of Krebs
cycle is the oxidation of acetyl coA forming CO2 along
with GTP, NADH, FADH2.
Anabolic Reaction of Krebs cycle
Krebs
cycle intermediates are used as precursors for the formation of various
cellular macromolecules.
Let’s
take some examples
1.Citrate+ATP+CoA→acetyl-CoA+oxaloacetate+ADP+Pi.
This reaction takes place in the cytoplasm and is a source of acetyl-CoA for
fatty acid biosynthesis.
2.α-Ketoglutarate
+ alanine↔glutamate + pyruvate.
3.α-Ketoglutarate→succinate
+ CO2. This reaction is involved in the hydroxylation of prolyl and lysyl
residues of protocollagen, a step in the synthesis of collagen.
4.Succinyl-CoA
+ glycine→Δ-aminolevulinic acid (ALA). ALA is then utilized for the synthesis
of heme.
5..Oxaloacetate
+ alanine↔aspartate + pyruvate.
As
citric acid cycle serves as both anabolic and catabolic pathway; it is called
amphibolic.