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This Lecture is made for 9th Biology Students. 9th Biology Chapter 8 Nutrition.
Topics:
1. Vitamin A
2. Vitamin B
3. Vitamin C
VITAMINS
Vitamins are the chemical compounds that are required in low amounts but are essential for
normal growth and metabolism. Vitamins may be divided into two groups: the fat-soluble vitamins
(vitamins A, D, E, and K) and the water-soluble vitamins (vitamins B and vitamin C).
Vitamin A
Vitamin A was the first fat-soluble vitamin identified (in 1913). It combines with a protein called
opsin to form rhodopsin in rod cells of the retina of eye. When vitamin A is inadequate, the lack
of rhodopsin makes it difficult to see in dim light. It is also involved in cell differentiation, a process
through which embryonic cells transform into mature cells with specific functions. Vitamin A also
supports bone growth and immune function
Cooking or heating destroys the water soluble vitamins more readily than the fat-soluble
vitamins.
Fat-soluble vitamins are much less excreted from the body as compared to water-soluble
vitamins. This means that levels of water-soluble vitamins in the body can decrease more
quickly, leading to vitamin deficiency.
Which of the major components of food is needed as the main
structural componet of the body
proteins
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Table 8.3: Functions, deficiencies and sources of important vitamins
Vitamin Sources Functions Deficiency symptoms
Vitamin
A
Leafy vegetables
(spinach, carrots)
Yellow fruits
Fish
Liver
Egg, milk and butter
Vision in dim light
Cell differentiation
Growth
Immunity
Poor growth
Blindness
Dry skin
Vitamin
C
Citrus fruits
Leafy green
vegetables
Beef liver
Collagen formation
Healing of wounds
Functioning of immune
system
Scurvy:
Fatigue, poor wound
healing
Bleeding gums & joints
Vitamin
D
Fish liver oil
Milk
Ghee and butter
Synthesized by skin
Maintenance of the
concentrations of calcium
and phosphorous
Rickets in children
Osteomalacia in adults
Minute quantities of vitamin C are present in muscles.Since meat consists of muscles so it is not
a good source of vitamin C.
Humans get vitamin A from leafy vegetables (spinach, carrots), yellow/orange fruits (mango), liver,
fish, egg, milk, butter etc. Deficiency of vitamin A is the leading cause of blindness in children
worldwide. One of the symptoms of vitamin-A deficiency is night blindness. It is a temporary
condition, but if left untreated it can cause permanent blindness. Vitamin-A deficiency can also
cause a condition in which hair follicles become plugged with keratin, giving dry texture to skin.
Vitamin C: (Ascorbic Acid)
Vitamin C participates in many reactions. It is needed to form collagen (a fibrous protein) that gives
strength to connective tissues. Collagen is also needed for the healing of wounds. Vitamin C in
white blood cells enables the immune system to function properly.
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We get vitamin C from citrus fruits (e.g. oranges, lemons, and grape fruit), leafy green vegetables,
beef liver etc. Deficiency of vitamin C causes connective tissue changes throughout the body. The
disease known as scurvy results from lack of vitamin C. In this condition the synthesized collagen
is unstable. Symptoms of scurvy include muscle and joint pain, swollen and bleeding gums, slow
wounds healing, and dry skin.
Vitamin D
The best-known function of vitamin D is to help regulate blood levels of calcium and phosphorous.
Vitamin D increases the absorption of these minerals from intestine and their deposition in bones.
Vitamin D is mainly found in fish liver oil, milk, ghee, and butter etc. It is also synthesized by skin
when ultraviolet (UV) radiations from the Sun are used to convert a compound into vitamin D.
Long-term deficiency of vitamin D affects bones. In children, vitamin-D deficiency leads to rickets,
a condition in which bones weaken and bow under pressure. In adults, vitamin-D deficiency causes
osteomalacia, or “softening of bones,”increasing the risk for fractures in bones.
