Biotin

Question 1

How is the structure of thiamine similar to biotin?

Answer 1

both thiamine and biotin have a thiol group

Question 2

How is biotin absorbed by the intestine?

Answer 2

SMVT1 - sodium-dependent multivitamin transporter

biotinidase - major binding-protein in the plasma

Question 3

What are the two metabolic functions of biotin?

Answer 3

functions in carboxylation reactions (similar to the function of vitamin K)

enzyme cofactor - carboxylation to catalyze essential metabolic reactions such as:
- acetyl-CoA to malonyl-CoA (using bicarbonate and ATP)

gluconeogenesis - assists in the conversion of oxaloacetate

Question 4

How are the metabolic functions of biotin similar to/different from those of thiamin?

Answer 4

thiamine is involved in glycolysis (fed state) for glucose metabolism - removes CO2 group

biotin is involved in gluconeogenesis (starved state) - adds CO2 group