Metabolic pathway

In biochemistry, a metabolic pathway is a linked series of chemical reactions occurring within a cell. The reactants, products, and intermediates of an enzymatic reaction are known as metabolites, which are modified by a sequence of chemical reactions catalyzed by enzymes.^[1]^: 26 In most cases of a metabolic pathway, the product of one enzyme acts as the substrate for the next. However, side products are considered waste and removed from the cell.^[2]

Different metabolic pathways function in the position within a eukaryotic cell and the significance of the pathway in the given compartment of the cell.^[3] For instance, the electron transport chain and oxidative phosphorylation all take place in the mitochondrial membrane.^[4]^{: 73, 74 & 109} In contrast, glycolysis, pentose phosphate pathway, and fatty acid biosynthesis all occur in the cytosol of a cell.^[5]^{: 441–442}

There are two types of metabolic pathways that are characterized by their ability to either synthesize molecules with the utilization of energy (anabolic pathway), or break down complex molecules and release energy in the process (catabolic pathway).^[6]

The two pathways complement each other in that the energy released from one is used up by the other. The degradative process of a catabolic pathway provides the energy required to conduct the biosynthesis of an anabolic pathway.^[6] In addition to the two distinct metabolic pathways is the amphibolic pathway, which can be either catabolic or anabolic based on the need for or the availability of energy.^[7]

Pathways are required for the maintenance of homeostasis within an organism and the flux of metabolites through a pathway is regulated depending on the needs of the cell and the availability of the substrate. The end product of a pathway may be used immediately, initiate another metabolic pathway or be stored for later use. The metabolism of a cell consists of an elaborate network of interconnected pathways that enable the synthesis and breakdown of molecules (anabolism and catabolism).

^ Nelson DL, Cox MM (2008). Lehninger principles of biochemistry (5th ed.). New York: W.H. Freeman. ISBN 978-0-7167-7108-1.
^ Alison S, Papachristodoulou DK, Despo K, Elliott WH, Elliott DC (2014). Biochemistry and molecular biology (Fifth ed.). Oxford. ISBN 978-0-19-960949-9. OCLC 862091499.{{cite book}}: CS1 maint: location missing publisher (link)
^ Nicholson DE (March 1971). An Introduction to Metabolic Pathways by S. DAGLEY (Vol. 59, No. 2 ed.). Sigma Xi, The Scientific Research Society. p. 266.
^ Harvey RA (2011). Biochemistry (5th ed.). Baltimore, MD: Wolters Kluwer. ISBN 978-1-60831-412-6.
^ Voet D, Voet JD, Pratt CW (2013). Fundamentals of Biochemistry: Life at the Molecular Level (4th ed.). Hoboken, NJ: Wiley. ISBN 978-0470-54784-7.
^ ^a ^b Reece JB, Campbell NA (2011). Campbell Biology (9th ed.). Boston: Benjamin Cummings / Pearson. pp. 143. ISBN 978-0-321-55823-7.
^ Berg JM, Tymoczko JL, Stryer L, Gatto GJ (2012). Biochemistry (7th ed.). New York: W.H. Freeman. p. 429. ISBN 978-1-4292-2936-4.

[Nelson-1] Nelson DL, Cox MM (2008). Lehninger principles of biochemistry (5th ed.). New York: W.H. Freeman. ISBN 978-0-7167-7108-1.

[2] Alison S, Papachristodoulou DK, Despo K, Elliott WH, Elliott DC (2014). Biochemistry and molecular biology (Fifth ed.). Oxford. ISBN 978-0-19-960949-9. OCLC 862091499.{{cite book}}: CS1 maint: location missing publisher (link)

[3] Nicholson DE (March 1971). An Introduction to Metabolic Pathways by S. DAGLEY (Vol. 59, No. 2 ed.). Sigma Xi, The Scientific Research Society. p. 266.

[Harvey-4] Harvey RA (2011). Biochemistry (5th ed.). Baltimore, MD: Wolters Kluwer. ISBN 978-1-60831-412-6.

[Voet,_Voet,_Pratt-5] Voet D, Voet JD, Pratt CW (2013). Fundamentals of Biochemistry: Life at the Molecular Level (4th ed.). Hoboken, NJ: Wiley. ISBN 978-0470-54784-7.

[Campbell-6] Reece JB, Campbell NA (2011). Campbell Biology (9th ed.). Boston: Benjamin Cummings / Pearson. pp. 143. ISBN 978-0-321-55823-7.

[7] Berg JM, Tymoczko JL, Stryer L, Gatto GJ (2012). Biochemistry (7th ed.). New York: W.H. Freeman. p. 429. ISBN 978-1-4292-2936-4.

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