Chapter 21, Problem 21.119EP

(a)

Interpretation Introduction

Interpretation: Among the given pair of molecules, the member which is encountered first in the biosynthetic pathway that produces active Vitamin ${\text{D}}_{\text{3}}$  from cholesterol has to be predicted.

Concept introduction: The most important forms of Vitamin D are Vitamin ${\text{D}}_{\text{2}}$ and Vitamin ${\text{D}}_{\text{3}}$.  Vitamin ${\text{D}}_{\text{2}}$ is found in the foods of plant origin.  Vitamin ${\text{D}}_{\text{3}}$ is produced in the skin of humans and animals.

(b)

Interpretation Introduction

Interpretation: Among the given pair of molecules, the member which is encountered first in the biosynthetic pathway that produces active Vitamin ${\text{D}}_{\text{3}}$ from cholesterol has to be predicted.

Concept introduction: The most important forms of Vitamin D are Vitamin ${\text{D}}_{\text{2}}$ and Vitamin ${\text{D}}_{\text{3}}$.  Vitamin ${\text{D}}_{\text{2}}$ is found in the foods of plant origin.  Vitamin ${\text{D}}_{\text{3}}$ is produced in the skin of humans and animals.