Final answer:
The vitamin involved in carboxylation reactions, formation of oxaloacetic acid for the citric acid cycle, and gluconeogenesis is biotin (vitamin B7).
Step-by-step explanation:
The vitamin that participates in carboxylation reactions, is required for the formation of oxaloacetic acid for the citric acid cycle, and is used in gluconeogenesis is biotin, also known as vitamin B7. Biotin-dependent enzymes play a crucial role in carboxylation reactions, where they facilitate the addition of a carboxyl group to various substrates, which is a fundamental process in the synthesis of oxaloacetic acid and gluconeogenesis.
Oxaloacetic acid is necessary for the citric acid cycle, a central metabolic pathway that generates energy in the form of ATP, while gluconeogenesis is the synthesis of glucose from non-carbohydrate sources.