1 16.9 Enzyme Cofactors Chapter 16 Amino Acids, Proteins, and Enzymes.
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Transcript of 1 16.9 Enzyme Cofactors Chapter 16 Amino Acids, Proteins, and Enzymes.
3
Water-Soluble Vitamins
Water-soluble vitamins are• soluble in aqueous solutions.• cofactors for many enzymes.• not stored in the body.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Fat-Soluble Vitamins
Fat-soluble vitamins• are A, D, E, and K. • are soluble in lipids, but not in aqueous solutions.• are important in vision, bone formation, antioxidants,
and blood clotting.• are stored in the body.
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
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Learning Check
Identify each compound as a
1) water-soluble vitamin 2) fat-soluble vitamin.
A. Folic acid
B. Retinol (Vitamin A)
C. Vitamin C
D. Vitamin E
E. Niacin
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Solution
Identify each compound as a
1) water-soluble vitamin 2) fat-soluble vitamin.
A. 1 Folic acid
B. 2 Retinol (Vitamin A)
C. 1 Vitamin C
D. 2 Vitamin E
E. 1 Niacin
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Thiamin (Vitamin B1)
Thiamin • was the first B vitamin identified.• is part of the coenzyme thiamin pyrophosphate (TPP), required in the decarboxylation of -keto carboxylic
acids.
• deficiency results in beriberi (fatigue, weight loss, and nerve degeneration).
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Riboflavin (Vitamin B2)
Riboflavin is• made of the sugar alcohol ribitol and flavin.• part of the coenzymes flavin adenine dinucleotide (FAD)
and flavin mononucleotide (FMN).• needed for good vision and healthy skin.
N
N N
NHH3C
H3C
CH2 CH CH CH CH2 OH
OHOHOH
O
O
D-Ribitol
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Niacin (Vitamin B3)
Niacin• is part of the coenzyme
nicotinamide adenine dinucleotide (NAD+) involved in oxidation-reduction reactions.
• deficiency can result in dermatitis, muscle fatigue, and loss of appetite.
• is found in meats, rice, and whole grains.
N
C
O
OH
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Pantothenic Acid (Vitamin B5)
Pantothenic acid• is part of coenzyme A needed for energy production
as well as glucose and cholesterol synthesis.• deficiency can result in fatigue, retarded growth,
cramps, and anemia.• is found in salmon, meat, eggs, whole grains, and
vegetables.
HO CH2 C CH C N CH2 CH2 C OH
O
H
OH OCH3
CH3
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Cobalamin (Vitamin B12)
Cobalamin• consists of four pyrrole
rings with a Co2+.• is a coenzyme for
enzymes that transfer methyl groups and produce red blood cells.
• deficiency can lead to pernicious anemia and nerve damage.
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Ascorbic Acid (Vitamin C)
Vitamin C• is required in collagen
synthesis.• deficiency can lead to
weakened connective tissue, slow-healing wounds, and anemia.
• is found in blueberries, citrus fruits, tomatoes, broccoli, red and green vegetables.
O CHOH
CH2OH
OHHO
O
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Folic Acid (Folate)
Folic acid (folate)• consists of pyrimidine, p-aminobenzoic acid, and glutamate.
• forms the coenzyme THF used in the transfer of carbon groups and the synthesis of nucleic acids.
• deficiency can lead to abnormal red blood cells, anemia, and poor growth.
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Vitamin A
Vitamin A• is obtained from meats and beta-carotenes in plants.• has beta-carotenes that are converted by liver
enzymes to vitamin A (retinol).
H3C CH3
CH3
CH3 CH3
CH3 CH3H3C CH3
H3C
CH3 CH3
CH2OHH3C CH3
CH3
Beta-carotene
Retinol (vitamin A)
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Vitamin D
Vitamin D (D3)• is synthesized in skin
exposed to sunlight. • regulates the absorption of
phosphorus and calcium during bone growth.
• deficiency can result in weakened bones.
• sources include cod liver oil, egg yolk, and enriched milk.
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Vitamin E
Vitamin E• is an antioxidant in cells.• may prevent the oxidation of unsaturated fatty acids.• is found in vegetable oils, whole grains, and
vegetables.
O
CH3
HO
H3C
CH3
CH3
CH3
CH3 CH3 CH3
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Vitamin K
• Vitamin K1 in plants has a saturated side chain.
• Vitamin K2 in animals has a long unsaturated side chain.
• Vitamin K2 is needed for the synthesis of zymogens for blood clotting.
3n
CH3
CH3
O
O CH3 CH3
Vitamin K2 (menaquinone)
CH3
CH3
O
O CH3 CH3
Vitamin K1 (phylloquinone)
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Learning Check
Identify the vitamin associated with each1) Thiamin (B1) 2) Vitamin A
3) Vitamin K 4) Vitamin D5) Ascorbic Acid
A. Collagen formationB. BeriberiC. Absorption of phosphorus and calcium in bone D. VisionE. Blood clotting