Step 1: Understanding Water-Soluble Vitamins
Water-soluble vitamins (B-complex and C) dissolve in water and are excreted in urine.
However, Vitamin B12 is an exception.
Step 2: Storage of Vitamin B12
Unlike other B vitamins, B12 is stored in the liver.
It plays a vital role in red blood cell formation and neurological functions.
Final Answer: Vitamin B12 is water-soluble but not excreted easily.
A tetrapeptide is made of naturally occurring alanine, serine, glycine, and valine. If the C-terminal amino acid is alanine and the N-terminal amino acid is chiral, the number of possible sequences of the tetrapeptide is: