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2025-02-18T05:06:58Z

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			File:Net_reactions_for_glycolysis_of_glucose,_oxidative_decarboxylation_of_pyruvate,_and_Krebs_cycle..png\|Net reactions for glycolysis, oxidative decarboxylation of pyruvate, and Krebs cycle
			File:Gluconeogenese_Schema_2.png\|Gluconeogenesis pathway
			File:Amphibolic_Properties_of_the_Citric_Acid_Cycle.gif\|Amphibolic properties of the citric acid cycle
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Prab at 20:28, 8 September 2023

2023-09-08T20:28:55Z

New page

== Metabolic Pathways ==

In the realm of [[biochemistry]], '''metabolic pathways''' refer to a series of interconnected chemical reactions taking place within a cell. These reactions, steered by enzymes and often necessitating certain dietary minerals, vitamins, and other cofactors, modify principal chemicals. Given the plethora of chemicals — commonly termed '''metabolites''' — involved, these pathways can be intricate. Multiple such pathways function simultaneously in a cell, collectively forming the '''metabolic network'''. These pathways are instrumental in ensuring an organism's [[homeostasis]].

=== Classification ===
Metabolic pathways are primarily classified into two categories:

* '''Catabolic Pathways''': These involve breaking down molecules and often yield energy.
* '''Anabolic Pathways''': These pathways are concerned with the synthesis of molecules, often utilizing energy.

These pathways are interdependent, often culminating in the creation of new biomolecules.

=== Functional Perspective ===

When a molecule, referred to as a '''substrate''', joins a metabolic pathway, it undergoes sequential modifications to transform into another product. Depending on the cellular needs and the molecule's availability, this product might:

* Be utilized immediately
* Kickstart another metabolic pathway, known as a '''flux generating step'''
* Be retained by the cell

The rate of a specific metabolic process might be influenced by the concentration of the intermediates and end-products of both anabolic and catabolic pathways.

=== Overview and Directionality ===

Each metabolic pathway is essentially a sequence of biochemical reactions connected via their intermediates. This means that a product of one reaction becomes the substrate for the succeeding one. While all chemical reactions are inherently reversible, a cell's conditions often make it more thermodynamically favorable for reactions to proceed in a specific direction.

For instance, while one pathway might synthesize a particular [[amino acid]], the degradation of this amino acid might be facilitated by a distinct pathway. However, exceptions exist. A case in point is the metabolism of glucose: while [[glycolysis]] breaks down glucose, some reactions within this pathway are reversible, aiding in glucose's re-synthesis ([[gluconeogenesis]]).

==== Glycolysis: A Historical Perspective ====

[[Glycolysis]] holds the distinction of being the earliest discovered metabolic pathway. A snapshot of its process is as follows:

* As glucose makes its entry into a cell, it undergoes immediate phosphorylation by ATP, turning into glucose 6-phosphate in a non-reversible first step.
* During periods of surplus lipid or protein energy sources, certain glycolysis reactions might function in reverse, producing glucose 6-phosphate. This is then stored either as glycogen or starch.
* Feedback inhibition often regulates metabolic pathways.

=== Cyclic Metabolic Pathways ===

Some metabolic pathways operate in a 'cyclic' manner. Here, each component of the cycle acts as a substrate for the succeeding reaction within the cycle. The [[Krebs Cycle]] exemplifies this.

=== Regulation and Separation in Eukaryotes ===

In [[eukaryotes]], anabolic and catabolic pathways often function separately. This separation can be:

* '''Physical''': Via compartmentalization within organelles.
* '''Biochemical''': Through the necessity of distinct enzymes and cofactors.

==Major metabolic pathways==
<center>{{metabolic pathways}}</center>
{{Clear}}
===Cellular respiration===
{{Main|Cellular respiration}}
Several distinct but linked metabolic pathways are used by cells to transfer the energy released by breakdown of [[fuel molecule]]s into [[Adenosine triphosphate|ATP]] and other small molecules used for energy (e.g. [[Guanosine triphosphate|GTP]], [[NADPH]], [[FADH]]).

These pathways occur within all living organisms in some form:
#[[Glycolysis]]
#[[Aerobic respiration]] and/or [[Anaerobic respiration]]
#[[Citric acid cycle]] / Krebs cycle (not in most obligate anaerobic organisms)
#[[Oxidative phosphorylation]] (not in obligate anaerobic organisms)

Synthesis of energetic compounds from non-living matter:
* [[Photosynthesis]] (plants, algae, [[cyanobacteria]])
==See also==
{{Portal|Metabolism}}
*[[Metabolism]]
*[[Metabolic network]]
*[[Metabolic network modelling]]
*[[Metabolic engineering]]
{{stub}}
{{metabolism}}
{{DEFAULTSORT:Metabolic Pathway}}
[[Category:Metabolism]]

Metabolic pathway - Revision history

Prab: CSV import

Prab at 20:28, 8 September 2023