from the gut in the presence of a gly-
coprotein called intrinsic factor; lack
of this factor or deÜciency of B 12 re-
sults in pernicious anaemia.
Other vitamins in the B complex
include nicotinic acid, pantothenic
acid, biotin, and lipoic acid. See also
choline.
A
- Information about IUPAC nomenclature
vitamin C (ascorbic acid)A colour-
less crystalline water-soluble vitamin
found especially in citrus fruits and
green vegetables. Most organisms
synthesize it from glucose but man
and other primates and various other
species must obtain it from their
diet. It is required for the mainte-
nance of healthy connective tissue;
deÜciency leads to scurvy. Vitamin C
is readily destroyed by heat and light.
A- Information about IUPAC nomenclature
vitamin DA fat-soluble vitamin oc-
curring in the form of two steroid de-
rivatives: vitamin D 2 (ergocalciferol,
or calciferol), found in yeast; and
vitamin D 3 (cholecalciferol), which oc-
curs in animals. Vitamin D 2 is formed
from a steroid by the action of ultra-
violet light and D 3 is produced by the
action of sunlight on a cholesterol
derivative in the skin. Fish-liver oils
are the major dietary source. The ac-
tive form of vitamin D is manufac-
tured in response to the secretion of
parathyroid hormone, which occurs
when blood calcium levels are low. It
causes increased uptake of calcium
from the gut, which increases the
supply of calcium for bone synthesis.
Vitamin D deÜciency causes rickets
in growing animals and osteomalacia
549 vitamin D
v
Vitamin D
O OOH OHCH 2OHOHVitamin C