What is the reactant in the gluconeogenic bypass of step 10?

In the gluconeogenic bypass of step 10, the reactant is bicarbonate. This step involves the conversion of pyruvate into oxaloacetate, which is a crucial reaction in gluconeogenesis. Pyruvate, when converted to oxaloacetate, requires the addition of carbon dioxide (which is in the form of bicarbonate in physiological conditions) and the enzyme pyruvate carboxylase. This reaction takes place in the mitochondria and is an important regulatory step in gluconeogenesis, ensuring that glucose can be synthesized from non-carbohydrate precursors.

The use of bicarbonate helps to facilitate the carboxylation of pyruvate to form oxaloacetate, effectively capturing the carbon necessary for gluconeogenesis. This process is also where ATP is utilized, stressing the energetic cost of synthesizing glucose from pyruvate.