Vitamin C is an essential water-soluble vitamin that cannot be synthesized by humans. It plays important roles in collagen formation, antioxidant activity, and iron absorption. The recommended daily allowance is 90 mg for adult men and 75 mg for women, though smokers may need an additional 35 mg. While deficiency can cause scurvy, too much vitamin C intake above 2000 mg daily can cause gastrointestinal issues.

1. Course-ConceptinBiological
Sciences
Topic- Vitamin C
• Submitted by-
• Avantika Chhonker
• (SC &RB)

2. INTRODUCTION
Vitamins
• A vitamin is an organic molecule that is an essential micronutrient that
an organism needs in small quantities for the proper functioning of its metabolism.
Essential nutrients cannot be synthesized in the organism, either at all or not in
sufficient quantities, and therefore must be obtained through the diet.
• Vitamins are classified as either water-soluble or fat-soluble.
• In humans there are 13 vitamins: 4 fat-soluble (A, D, E, and K) and 9 water-soluble
(8 B vitamins and vitamin C).
• Water-soluble vitamins dissolve easily in water and, in general, are readily excreted
from the body, to the degree that urinary output is a strong predictor of vitamin
consumption. Because they are not as readily stored, more consistent intake is
important.
• Fat-soluble vitamins are absorbed through the intestinal tract with the help
of lipids (fats). Vitamins A and D can accumulate in the body, which can result in
dangerous hypervitaminosis.
• Fat-soluble vitamin deficiency due to malabsorption is of particular significance
in cystic fibrosis

3. VITAMIN C
• Vitamin C is well known for its ability to treat
Scurvy.
• It is water soluble vitamin, also know as
ascorbic acid.
• Vitamin C has three major roles:
1. Firstly, it catalyzes the hydroxylation reactions
especially prolyl and lysyl residues of collagen.
Thus, promoting the formation of connective
tissues and bones.
2. Secondly, it actively participates in anti-
oxidation. It is very powerful reductant.
3. Thirdly, it helps in the absorption of iron from
the intestine.

4. Properties of Ascorbic acid (Vitamin C):
• Ascorbic acid is a colourless and odourless crystalline substance.
• It is slightly sour in taste and optically active.
• Only the L-isomer has antiscorbutic properties.
• It is water-soluble and dissolves in alcohol too.
• It is not soluble in chloroform, solvent ether and light petroleum.
• It is readily oxidized, particularly in the presence of copper and iron but not
of aluminium.
• It is for this reason that the foods cooked in copper utensils lose ascorbic acid
quickly.
• This vitamin is also quickly deformed by alkalies.
• However, it is stable in weak acid solutions.
• This is why, baking soda shows a deleterious effect however, cooking in steam
degrades very little amount of ascorbic acid.
• Loss of ascorbic acid occurs in case of drying of vegetables and their storage.
• Freezing has no harmful effect on this vitamin.
• Little loss of ascorbic acid occurs when citrus fruit juices and tomato juice are
canned.
• Because of its easily oxidizable nature, the ascorbic acid is a powerful
reducing agent.
C6H8O6 Ascorbic Acid
Molecular Weight/
Molar Mass
176.12 g/mol
Density 1.694 g/cm
3
Boiling Point 553 °C
Melting Point 190 °C
Properties of Ascorbic Acid – C6H8O6

5. RECOMMENDED DIETARY ALLOWANCE
RDA:
The Recommended Dietary Allowance for adults 19 years and older is 90
mg daily for men and 75 mg for women.
For pregnancy and lactation, the amount increases to 85 mg and 120 mg
daily, respectively.
Smoking can deplete vitamin C levels in the body, so an additional 35 mg
beyond the RDA is suggested for smokers.
UL:
The Tolerable Upper Intake Level is the maximum daily intake unlikely
to cause harmful effects on health.
The UL for vitamin C is 2000 mg daily; taking beyond this amount may
promote gastrointestinal distress and diarrhea.
Only in specific scenarios, such as under medical supervision or in
controlled clinical trials, amounts higher than the UL are sometimes used.

6. Biosynthesis of Vitamin C:
• Source of vitamin C is plants. However, many animals can synthesize ascorbic acid from glucose by uronic
acid pathway.
• However, Human and other primates, guinea pigs and bats cannot synthesize ascorbic acid due to the
deficiency of a single enzyme L-gulonolactoneoxidase.
• The enzyme L- gluconolactone oxidase is required to convert L-glucono-1,4-lactone into L-ascorbic acid
in final step of the pathway.

7. Steps involved in formation of Vit-C
• The biosynthesis of ascorbic acid starts with the formation of UDP-glucuronic acid.
UDP-glucuronic acid is formed when UDP-glucose undergoes two oxidations catalyzed by the
enzyme UDP-glucose 6-dehydrogenase.
UDP-glucose 6-dehydrogenase uses the co-factor NAD+ as the electron acceptor.
• The transferase UDP-glucuronate pyrophosphorylase removes a UMP and glucuronokinase,
with the cofactor ADP, removes the final phosphate leading to D-glucuronic acid.
• The aldehyde group of this is reduced to a primary alcohol using the enzyme glucuronate
reductase and the cofactor NADPH, yielding L-gulonic acid.
• This is followed by lactone formation with the hydrolase gluconolactonase between the
carbonyl on C1 and hydroxyl group on the C4.
• L-Gulonolactone then reacts with oxygen, catalyzed by the enzyme L-gulonolactone oxidase
(which is nonfunctional in humans and other primates) and the cofactor FAD+.
This reaction produces 2-oxogulonolactone, which spontaneously undergoes enolization to
form ascorbic acid.

8. • Deficiency of Vitamin C:
Vitamin C deficiency results in scurvy (a disease characterized by the spongy
and sore gums, loose teeth), anemia, swollen joints and fragile blood vessel.
Lack of adequate Vitamin C results in reduced immune-competence.
Vitamin C deficiency also results in sluggish hormonal function of adrenal
gland and gonads.
Hemorrhage and osteoporosis are caused by deficiency of Vitamin C.
Also, delayed wound healing occurs in deficiency of vitamin C.
• Megadoses of vitamin C (Hypervitaminosis C):
High doses of Vitamin C ,300-400 times exceeding the normal
value(18gm) can be used in the treatment of common cold,
trauma and prevention of onset of diseases such as cataract,
coronary heart diseases, and onset of tumor.