Pentose phosphate pathway

A glucose-metabolizing pathway that generates NADPH and ribose-5-phosphate without directly producing ATP. Its oxidative and nonoxidative branches serve distinct metabolic needs.

Oxidative pentose phosphate pathway: The branch that oxidizes glucose-6-phosphate to ribulose-5-phosphate, producing NADPH and carbon dioxide. This branch supplies NADPH and releases one carbon from glucose as carbon dioxide.
Ribose 5-phosphate: A five-carbon sugar phosphate used to build nucleotides and other cellular molecules. The pathway supplies this precursor for nucleotide production.
Glycolysis: A sequence of reactions that converts glucose into pyruvate while capturing energy and reducing equivalents. The pathway exchanges sugar phosphates with glycolysis, linking carbon and energy metabolism.
Embden–Meyerhof–Parnas pathway: The conventional glycolytic route that converts glucose to pyruvate while producing ATP and NADH. Unlike this pathway, it directly captures ATP during glucose breakdown.
Nonoxidative pentose phosphate pathway: A set of reversible sugar-phosphate reactions that interconvert pentoses and glycolytic intermediates. It redirects pentose carbon toward nucleotide synthesis or back into glycolysis.
Glutathione: A tripeptide antioxidant that cells maintain in reduced form to limit oxidative damage. NADPH from the pathway helps regenerate reduced glutathione.
Glucose-6-phosphate: A phosphorylated glucose molecule that serves as a central branch point in carbohydrate metabolism. It is the pathway’s entry substrate and can also proceed through glycolysis.
Entner–Doudoroff pathway: An alternative route for glucose catabolism found in many bacteria and some archaea. It is another glucose-processing route, but yields different products and energy.
Glucose-6-phosphate dehydrogenase: An enzyme that catalyzes the first, rate-controlling reaction of the oxidative pentose phosphate pathway. Its activity commits glucose-6-phosphate to the NADPH-producing branch.
Fatty acid synthesis: The metabolic process that builds fatty acids from acetyl-CoA using reducing power. NADPH supports the reductive steps of fatty acid production.

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