Cells, Sugars, and Polysaccharides

By Jennifer Stearns, Michael Surette

Cells can use sugars for all sorts of other things. For example, the backbone of peptidoglycan, a major component of the bacterial cell wall, is made of sugars. Hexoses are six-carbon sugars like glucose, and pentoses are five-carbon sugars like ribose.

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When hexoses need to be made, they’re synthesized with gluconeogenesis using intermediates from glycolysis and the citric acid cycle. Pentoses can be made by removal of one carbon from a hexose.

Polysaccharides are molecules made up of many sugar subunits. In prokaryotes, they’re synthesized from activated glucose. There are two forms of activated glucose; each is used to make different types of polysaccharides:

  • Uridine diphosphoglucose (UDPG) is the precursor for the backbone of the cell wall component peptidoglycan, a precursor in parts of the Gram-negative outer membrane and a precursor of the storage molecule glycogen.

  • Adenosine diphosphoglucose (ADPG) is the precursor of the storage molecule glycogen.

The process of making a polysaccharide involves adding an activated glucose to the growing chain of a polysaccharide.