Transcript Chapter 16 Amino Acids, Proteins, and Enzymes 16.9 Enzyme Cofactors Function of Coenzymes A coenzyme prepares the active site for catalytic activity.

Chapter 16 Amino Acids,
Proteins, and Enzymes
16.9
Enzyme Cofactors
1
Function of Coenzymes
A coenzyme prepares the active site for catalytic activity.
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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
4
Learning Check
Identify each compound as a
1) water-soluble vitamin 2) fat-soluble vitamin.
A.
B.
C.
D.
E.
Folic acid
Retinol (Vitamin A)
Vitamin C
Vitamin 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.
O
H3C
N
H3C
N
N
N
H
O
D-Ribitol
CH2 CH CH CH CH 2 OH
OH OH OH
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Niacin (Vitamin B3)
Niacin
• is part of the coenzyme
nicotinamide adenine
dinucleotide (NAD+)
involved in oxidationreduction reactions.
• deficiency can result in
dermatitis, muscle fatigue,
and loss of appetite.
• is found in meats, rice, and
whole grains.
O
C
OH
N
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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.
CH 3 OH O
HO CH2 C
CH 3
O
CH C N CH 2
CH2 C OH
H
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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.
CH2OH
O
HO
O
CHOH
OH
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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
Beta-carotene
CH3
CH3
CH3
H3C
H3C
CH3
CH3
CH3
CH3
H3C
CH3
CH3
CH2OH
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.
CH 3
HO
CH 3
H 3C
O
CH 3
CH 3
CH 3
CH 3
CH 3
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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.
O
O
CH3
CH3
CH3
CH3
3
O
CH3
CH3
Vitamin K1 (phylloquinone)
n
O
CH3
CH3
Vitamin K2 (menaquinone)
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Learning Check
Identify the vitamin associated with each
1) Thiamin (B1)
2) Vitamin A
3) Vitamin K
4) Vitamin D
5) Ascorbic Acid
A.
B.
C.
D.
E.
Collagen formation
Beriberi
Absorption of phosphorus and calcium in bone
Vision
Blood clotting
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Solution
Identify the vitamin associated with each
1) Thiamin (B1)
2) Vitamin A
3) Vitamin K
4) Vitamin D
5) Ascorbic Acid
A.
B.
C.
D.
E.
5
1
4
2
3
Collagen formation
Beriberi
Absorption of phosphorus and calcium in bone
Vision
Blood clotting
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