Activated sugars in anabolism: Which nucleoside diphosphate is most commonly used to activate monosaccharides for carbohydrate biosynthesis (for example, UDP-glucose in glycogen and cell wall assembly)?

Introduction / Context:
Sugar nucleotides serve as activated donors in the biosynthesis of polysaccharides, glycoconjugates, and cell wall components. Recognizing which nucleoside diphosphate predominates helps in understanding pathways in bacteria and eukaryotes alike.

Given Data / Assumptions:

• Examples include UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine.
• Role is transfer of glycosyl units to acceptors via glycosyltransferases.
• We are asked for the most common nucleoside diphosphate used.

Concept / Approach:

Uridine diphosphate (UDP) forms sugar nucleotides extensively (e.g., UDP-glucose), serving as donors in glycogen synthesis, peptidoglycan, lipopolysaccharide core sugars, and glycoprotein assembly. While ADP-, GDP-, and CMP-linked sugars exist (e.g., GDP-mannose, CMP-sialic acid), UDP-sugars are the most prevalent in many anabolic carbohydrate reactions.

Step-by-Step Solution:

Verification / Alternative check:

Biochemistry references list UDP-sugars as central intermediates in glycogenesis and cell wall biosynthesis across taxa.

Why Other Options Are Wrong:

ADP and GDP are used for certain sugars (e.g., GDP-mannose) but not “most often.”

“Thymine diphosphate” is not a standard sugar nucleotide in carbohydrate anabolism.

Common Pitfalls:

Assuming all sugar nucleotides are equally common; overlooking the dominance of UDP-linked sugars in core pathways.

Final Answer:

Uridine diphosphate