1.THe biologically active form of Vit B12 is present in two forms. Either as methylcobalamin or adenosylcobalamin. Active form is measured as holotranscobalamin. 2. Intrinsic factor is produced by the parietal cells of the stomach. It is necessary for the absorption of dietary Vit B12. Deficiency of intrinsic factor results in pernicious anemia 3. R-protein binds to Vit B12 for the transport of the Vitamin-Protein complex. Solution 1.THe biologically active form of Vit B12 is present in two forms. Either as methylcobalamin or adenosylcobalamin. Active form is measured as holotranscobalamin. 2. Intrinsic factor is produced by the parietal cells of the stomach. It is necessary for the absorption of dietary Vit B12. Deficiency of intrinsic factor results in pernicious anemia 3. R-protein binds to Vit B12 for the transport of the Vitamin-Protein complex..