Question

the biotin coenzyme participates in the synthesis of glucose and fatty acids by adding ______ to compounds.
multiple choice

water

carbon dioxide

nitrogen

phosphate groups

Explanation:

Biotin is a coenzyme involved in carboxylation reactions. In the synthesis of glucose (gluconeogenesis) and fatty acids (fatty - acid biosynthesis), carboxylation reactions add carbon dioxide ($CO_2$) to compounds. For example, in gluconeogenesis, pyruvate carboxylase (which uses biotin) adds $CO_2$ to pyruvate to form oxaloacetate. Water is involved in hydrolysis reactions, nitrogen in processes like amino - acid metabolism (not the main role in the context of biotin - related glucose and fatty - acid synthesis as described), and phosphate groups are added in phosphorylation reactions (catalyzed by kinases, not biotin - dependent reactions in this context).

Answer:

carbon dioxide