from the gut in the presence of a glycoprotein called intrinsic factor; lack
of this factor or deÜciency of B 12 results 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 colourless 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 maintenance of healthy connective tissue;
deÜciency leads to scurvy. Vitamin C
is readily destroyed by heat and light.
A
• Information about IUPAC nomenclature
vitamin D A fat-soluble vitamin occurring in the form of two steroid derivatives: vitamin D 2 (ergocalciferol,
or calciferol), found in yeast; and
vitamin D 3 (cholecalciferol), which occurs in animals. Vitamin D 2 is formed
from a steroid by the action of ultraviolet 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 active form of vitamin D is manufactured 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
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GTIQECNEKHGTQN
EJQNGECNEKHGTQN
Vitamin D
O
O
OH
O
H
CH 2
O
H
O
H
Vitamin C
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