Module 07: Vitamins (Stoker) Flashcards
1
Q
These are organic compounds that cannot be synthesized in enough amounts by the human body and must be obtained from dietary sources. They are sometimes cofactors in some conjugated enzymes.
A
Vitamins
2
Q
In what kind of quantities are vitamins measured?
A
Micro and Milligram quantities
3
Q
What are the two generic families of vitamins?
A
(1) Water Soluble Vitamins
(2) Fat Soluble Vitamins
4
Q
What is the difference between water soluble vitamins and fat soluble vitamins in terms of absorption?
A
Water soluble vitamins: Directly into the blood
Fat soluble vitamins: First enter into the lymph system
5
Q
What is the difference between water soluble vitamins and fat soluble vitamins in terms of transport?
A
Water soluble vitamins: They travel without carriers
Fat soluble vitamins: They entail (require) protein carriers
6
Q
What is the difference between water soluble vitamins and fat soluble vitamins in terms of storage?
A
Water soluble vitamins: They circulate in water-filled parts of the body
Fat soluble vitamins: They are formed in the cells associated with fat
7
Q
What is the difference between water soluble vitamins and fat soluble vitamins in terms of excretion?
A
Water soluble vitamins: They are removed by the kidneys in the form of urine
Fat soluble vitamins: They tend to remain in fat storage sites
8
Q
What is the difference between water soluble vitamins and fat soluble vitamins in terms of toxicity?
A
Water soluble vitamins: They are not likely to reach toxic levels when consumed from supplements
Fat soluble vitamins: They are likely to reach toxic levels when consumed from supplements.
9
Q
What is the difference between water soluble vitamins and fat soluble vitamins in terms of dosage frequency?
A
Water soluble vitamins: needed frequent doses
Fat soluble vitamins: needed in periodic doses
10
Q
What is the difference between water soluble vitamins and fat soluble vitamins in terms of coenzymes?
A
Water soluble vitamins: function as coenzymes
Fat soluble vitamins: do not function as coenzymes
11
Q
What enzymes participate in the transfer of H+ and e-?
A
(1) nicotinamide adenine dinucleotide (NAD+) and Nicotinamide adenine dinucleotide phosphate (NADP)
(2) Flavin mononucleotide (FMN) and flavin dinucleotide (FAD)
(3) Coenzyme Q
12
Q
What carry groups carry acyl group?
A
(1) Thiamine pyrophosphate (TPP)
(2) Lipoic Acid
(3) Coenzyme A
13
Q
This carries amino group transfer.
A
Pyridoxal Phosphate
14
Q
This is entailed for the activation and transfer of CO2
A
Biocytin
15
Q
This is entailed for one carbon group transfer
A
Tetrahydrofolic acid
16
Q
This carries alkyl groups.
A
Cobamide coenzyme
17
Q
How is NADH reduced to NADPH?
A
(a) Nicotinamide adenine dinucleotide, NAD+, and its phosphorylated analog NADP+ undergo reduction to NADH and NADPH, accepting a hydride ion (two electrons and one proton) from an oxidizable substrate. The hydride ion is added to either the front (the A side) or the back (the B side) of the planar nicotinamide ring.
17
Q
What is the reduced form of NAD?
A
nicotinamide adenine dinucleotide phosphate (NADPH)
18
Q
What is the oxidized form of NADPH?
A
nicotinamide adenine dinucleotide (NAD+)
19
Q
NAD and NADP are coenzyme forms of what?
A
Niacin (Vitamin B3)
20
Q
What are the reactions involving nicotinamide adenine dinucleotide (NAD+)
A
lactate DH, malate DH, pyruvate DH complex
21
Q
What are the reactions involving nicotinamide adenine dinucleotide phosphate (NADPH)
A
glucose-6P-DH and NADPH in fatty acid synthase complex
22
Q
NADP+ contains what?
A
contains a P group on 2’C of adenine ribose
23
Q
This accepts a H-(hydride ion) and a H+ is released to the medium.
A
nicotinamide adenine dinucleotide (NAD+)
24
How does nicotinamide adenine dinucleotide (NAD+) participate in redox reactions?
by accepting H- ions
25
NAD + -dependent dehydrogenases are often involved in ____________.
catabolism
26
NADP + -dependent dehydrogenases in ______________.
anabolism
27
How is FADH+ (FMNH+) reduced to FADH2 (FMNH2)?
Oxidized and reduced FAD and FMN. FMN consists of the structure above the dashed line on the FAD (oxidized form). The flavin nucleotides accept two hydrogen atoms (two electrons and two protons), both of which appear in the flavin ring system. When FAD or FMN accepts only one hydrogen atom, the semiquinone, a stable free radical, forms.
28
This is referred to as the stable free radical, forms.
Semiquinone
29
FAD and FMN are coenzyme forms of what?
Riboflavin (Vitamin B2)
30
What are the reactions involved with flavin adenine dinucleotide (FAD)?
succinic acid DH, (CAC), fatty acyl CoA DH
31
What are the reactions involved with flavin adenine mononucleotide(FAM)?
L-amino acid oxidase
32
Riboflavin consists of what?
Riboflavin consists of heterocyclic ring isoalloxazine/ flavin and ribitol attached to N10
33
flavin adenine mononucleotide(FAM) is composed of what?
P group esterified to 5’OH of ribitol
34
flavin adenine dinucleotide (FAD) is composed of what? flavin adenine dinucleotide (FAD)?
has an adenosine linked by pyrophosphate bridge to riboflavin (ribitol plus flavin)
35
How is the semiquinone formed?
Both FAD and FMN can accept and donate 2e- in the isoalloxazine ring. The isoalloxazine ring accepts and transfers e- and protons in a stepwise manner forming a semiquinone
36
How are flavin coenzymes bounded to the enzyme (prosthetic group?
bound lightly or covalently
37
This is referred to as a a mitochondrial electron carrier (coenzyme Q) (n=4 to 8)
Ubiquinone
38
This is a lipid soluble component of ETC found in inner mitochondria membrane. It is not a vitamin because it is produced by the body
Ubiquitous
39
Ubiquitous is involved in what
the conversion of food into energy.
40
What is the side chain of Ubiquitous
The side chain consists of variable repeating isoprenoid units
41
What is the oxidized form of Ubiquitous ?
Ubiquinone
42
What is the reduced form of Ubiquitous?
ubiquinol (hydroquinone)
43
What is the reaction of Ubiquinone?
NADH + H+ –> CoQH2 (complex I) of the respiratory chain.
44
This is the activated form of pantothenic acid (Vitamin B5)
Coenzyme A
45
Coenzyme A participates in what?
in activation reactions through transfer of acyl groups (RC=O-)
46
What are the reactions related to coenzyme A?
fatty acyl CoA synthase, dihydrolipoyl transacetylase of PDH complex
47
How does coenzyme a participate in acyl group transfers?
Some coenzymes containing adenosine. The adenosine portion is shaded in light red. Coenzyme A (CoA) functions in acyl group transfer reactions; the acyl group (such as the acetyl or acetoacetyl group) is attached to the CoA through a thioester linkage to the β-mercaptoethylamine moiety.
48
In what transfer does NAD+ participate in?
Hydride Transfers
49
In what transfer does FAD participate in?
Electron Transfers
50
What is the active form of vitamin B12?
adenosine is 5′-deoxyadenosylcobalamin,
51
In what transfer does adenosine is 5′-deoxyadenosylcobalamin participate in?
in intramolecular group transfers between adjacent carbons.
52
What is the reactive portion of coenzyme A?
free sulfhydryl at one end of the molecule
53
What bond can coenzyme A form with acetate and acyl?
Thioester Bond
54
What is the optimal integrality of Coenzyme A in the Krebs Cycle?
It acts as a fuel for the Krebs cycle.
55
What is the relationship between fatty acids and coenzyme A?
Fatty acids are activated once attached to Acyl Coenzyme A (CoA)
56
This is derived from thiamin (vitamin B1) and is used by many carboxylases and oxidative decarboxylases.
Thiamine Pyrophosphate, TPP
57
What are transketolases?
move 2 carbons at a time between sugars with keto groups
58
What is the reactive center of Thiamine Pyrophosphate, TPP?
Thiazolium ring (active site at C2 of the thiazole ring. The H at C2 is acidic, ionizes readily, releasing a H+ and forms a carbanion center.)
59
What kind of transfer is Thiamine Pyrophosphate, TPP involved in?
Transfer of Aldehyde Group
60
What are the reactions involved to Thiamine Pyrophosphate, TPP?
pyr decarboxylase of pyr DH complex, transketolases
61
Explain the reaction behind the Thiamine Pyrophosphate, TPP?
(1) The carbanion center binds and transfers active aldehyde and ketol groups
(2) Bonds to R1 and R2 labilized for loss leaving electron on carbonyl group, where there is the low-energy carbanion
62
What inactivates Thiamine Pyrophosphate, TPP?
It requires Mg+2 for activity. TPP is inactivated by thiaminase which is found in raw fish.
63
The Pyridoxal Phosphate exists in 2 forms: what kinds?
(1) Pyridoxal P
(2) Pyridoxamine P
64
This is is the tightly bound coenzyme of aminotransferases / transaminase.
Pyridoxal 5'-phosphate (PLP)
65
In what kind of transfer is Pyridoxal 5'-phosphate (PLP) involved in?
They are involved in the transfer of amino groups.
66
Where is Pyridoxal 5'-phosphate (PLP) derived from?
Derived from Vitamin B6/ Pyridoxine, pyridoxal, pyridoxamine
67
Pyridoxal 5'-phosphate (PLP) is prosthetic group for many amino-acid-related enzymes, particularly __________
transaminases
68
Pyridoxal 5'-phosphate (PLP) is the derivative of what vitamin?
B6 - Pyridoxine
69
What does Pyridoxal 5'-phosphate (PLP) form?
It forms an enzyme bound Schiff base intermediate that can rearrange in various ways.
70
What does the rearrangement of Pyridoxal 5'-phosphate (PLP) form?
rearrangement forms an a keto acid and enzyme bound pyridoxamine phosphate (PMP), which forms a Schiff base with a second keto acid
71
This is vitamin B7 and is involved in carboxylation reactions.
Biotin/ Biocytin (coenzyme)
72
What kind of transfer is Biotin/ Biocytin (coenzyme) involve in?
Used in reactions that transfer carboxyl groups and in ATP-dependent carboxylations
73
Biotin/ Biocytin (coenzyme) is composed of what?
Consists of imidazolone ring fused with tetrahydrothiophene linked to valeric acid.
74
Where is Biotin/ Biocytin (coenzyme attached to?
Covalently attached to lysine in carboxylase enzyme
75
Biocytin is covalently attached to lysine in carboxylase enzyme to form _____________
Biotin
76
What reactions are involved in Biotin/ Biocytin
acetyl CoA carboxylase, pyruvate carboxylase, propionyl carboxylase, methylmalonyl CoA carboxylase,
76
What does Biotin/ Biocytin do?
Accepts ATP-activated carboxyl group
and transfers it to carboxyl group acceptor
77
This inhibits the synthesis of biotin and biocytin. It is also known as a protein found in raw egg white.
Avidin
78
Tetrahydrofolate (THF) is composed of what?
(1) Pteridine
(2) P-aminobenzoic acid
(3) Glutamate
79
These in Tetrahydrofolate (THF) can carry one carbon functional group and are in boldface.
N6 and N10
80
How is Tetrahydrofolate formed?
Folate (Dihydrofolate Reductase) -Dihydrofolate (Dihydrofolate Reductase) ->Tetrahydrofolate
81
Tetrahydrofolate is known as the what?
Primary donor of one-carbon units (formyl-CHO, methylene-CH2, methyl, methenyl-CH=,formimino-CH=NH)
82
What inhibits the synthesis of Tetrahydrofolate?
folate antagonists such as methotrexate and sulfonamides
83
This is cancer chemotherapeutic: cancer needs more thymidylate than healthy cells (- DHFR)
methotrexate
84
This is cancer chemotherapeutic: cancer needs more ____________than healthy cells (- DHFR)
thymidylate
85
This is a antibacterial antibiotic:. In this bacterial Dihydrofolate reductases are somewhat different from eukaryotic DHFR because bacteria derive DHF from other sources; humans get it from folate.
Trimethoprim
86
What does tetrahydrofolate supply?
Supplies methyl group for thymidylate
87
This is the largest B vitamin
Cobamide/Cobalamin
87
Cobamide/Cobalamin is composed of what?
Corrin ring structure related to heme but missing one carbon in ring structure
88
This is responsible for the red color of Cobamide/Cobalamin?
Cobalt bound in core of ring system
89
What kind of enzymatic rearrangements is Cobamide/Cobalamin involved in?
(1) Catabolism of odd-chain fatty acids
(2) Methylation of homocysteine
90
What does Coenzyme B12 (Cobalamin) contain?
org molecule & an essential trace element cobalt
91
The 5th coordination position of cobalamin is with "____________"
dimethylbenzimidazole ribonucleotide
92
The 6th coordination position of cobalamin is with "____________"
linked to 5’-deoxyadenosyl cobalamin or methyl.
93
What are the active forms of Vitamin B12
(1) Methylcobalamin
(2) 5-deoxyadenosyl-cobalamin
94
Adenosyl-Cobalamin is composed of what?
(1) Missing carbon
(2) Reactive Co-C Bond
(3) 2 pyrrole rings attached (Linked) Directly
95
What are the two active forms of Adenosyl-Cobalamin?
1. d-adenosyl cobalamin
2. methylcobalamin/MeB12
96
Adenosyl-Cobalamin participates in what?
Participates in racemization and methylation reactions
97
This is the commercial form vitamin B12
cyanocobalamin
98
cyanocobalamin (readily avaiable commercial form is composed of what?
it contains a cyano group attached to the 6th coordination position
99
What happens in 5’-deoxyadenosylcobalamin
cyano group is replaced by 5’-deoxyadenosyl covalently attached to Co+3.
100
This is the cofactor for methylmalonyl CoA mutase,
5’-deoxyadenosylcobalamin
101
Where is cobalamin found?
Dietary sources are of animal origin, absent in plant foods, strict vegetarians are at risk of developing deficiency
102
What does the absorption of cobalamin require?
IF (glycoprot) secreted by parietal cells of gastric mucosa
103
How much vitamin B12 is stored in the liver that can amount to the daily metabolic requirement for 2000 days?
1mg (when supply is interrupted, deficiency appears after 5 years)
104
This pertains to the failure to absorb vitamin B12efficiently from the intestine where it is synthesized by intestinal bacteria. Individuals with this disease do not produce sufficient IF a glycoprot needed for B12 absorption
Pernicious anemia
105
This is a protein-bound form of lipoic acid wherein disulfides break periodically. An example of this is pyruvate dehydrogenase complex.
Lipoamide
106
what does lipoamide contain?
Contains five-membered disulfide ring
107
Where is lipoamide covalently bonded?
Covalently bound via amide to protein lysine sidechain
108
Lipoamide is involved in what?
Covalently bound via amide to protein lysine sidechain
109
lipoamide is chemically named as
6,8-dithiooctanoic acid or thioctic acid.
110
Lipoamide exists in 2 forms, which are?
(1) Cyclic or Oxidized
(2) Open or Reduced form (dihydrolipoic acid)
111
The S in lipoamide is in charge of what?
accepts and transfers acyl groups and H+ during oxidative decarboxylation of α-keto acids ex. Pyruvate
112
Why don't humans synthesize vitamins?
(1) Complex metabolites require energy for synthesis
(2) Control of their synthesis is also metabolically expensive
(3) Cheaper in the long run to derive these nutrients from diet
113
This can make almost everything (vitamins) given its energy and source of atoms.
E-coli
114
What broad classifications are used to identify water soluble vitamins?
Coenzymes or coenzyme precursors
Energy production
115
What broad classifications are used to identify fat soluble vitamins?
Antioxidants
Vision, bone health, coagulation
116
what is vitamin B1 and what does it produce?
thiamin (produces TPP)
117
what is vitamin B2 and what does it produce?
riboflavin (produces FAD, FMN)
118
what is vitamin B3 and what does it produce?
niacin (produces NAD+, NADP+)
119
what is vitamin B5 and what does it produce?
pantothenate (produces Coenzyme A)
120
what is vitamin B6 and what does it produce?
pyridoxamine (produces PLP)
121
what is vitamin B7 and what does it produce?
Biotin
122
what is vitamin B9 and what does it produce?
folate: produces THF, THF derivatives
123
what is vitamin B12 and what does it produce?
cobalamin (produces adenosylcobalamin, methylcobalamin)
124
Deficiency in niacin can lead to what
Pellagra: dermatitis, diarrhea, dementia
125
Where can humans synthesize nicotinamide.
tryptophan
126
Deficiency of thiamine can result in
(1) Beriberi: primary symptoms are in nervous system and musculature, difficulty in walking, paralysis of feet.
(2) Polished rice is missing in thiamine; rice hulls are rich in it
127
Deficiency of cobalamin can result in
(pernicious anemia): weakness, fatigue, pallor, palpitations, dizziness
128
How much of the human population can be affected in the deficiency of cobalamin?
5-40%
129
What is the function of vitamin C?
Functions as a cofactor in the formation of collagen and is involved in metabolism of certain amino acids
130
How much vitamin C is needed by humans?
100 mg/day saturates all body tissues - Excess vitamin is excreted
131
What are the two forms of vitamin C?
Reduced (RA) and oxidized form (OA)
132
Vitamin C can be synthesized by what?
L-gluonic acid
133
This is a post-translational modification that occurs to prolines within collagen.
Proline + O2 + -ketoglutarate + ascorbate 4-hydroxyproline + succinate + CO2 + dehydroascorbate
134
In the PTM role of ascorbate, these help stabilize the collagen triple helix
hydroxylated prolines
135
In the PTM role of ascorbate, this is known as the oxidoreductase
hydroxylase
136
This are the two cofactors needed by hydroxylases for the synthesis of collagen
Fe+2 and ascorbic acid
137
In the PTM role of ascorbate, this is needed to keep iron in the +2 state. It serves as a reducing agent (antioxidant)
ascorbic acid
138
Ascorbate deficiency can lead to?
collagen degradation, leading to scurvy
139
These are absorbed in intestine, carried via bile salts wherein most are formally built from isoprene units, as are steroids
Lipid Vitamins
140
Lipid vitamins are composed of what
(1) Contain rings & long aliphatic sidechains
(2) At least one polar group in each
(3) isoprene units, as are steroids
141
Preformed vitamin A are called _____________ derived from animal sources.
retinoids (retinol, retinal and retinoic acid
142
Plants provide _________ which are precursor forms of vitamin A or provitamin A
carotenoids
143
This is the major carotenoid which can be cleaved to two molecules of vitamin A. Present in yellow fruits and vegetables.
B-carotene
144
B-carotene is known as a
nonpolar dimer
145
This has 3 forms varying in terminal polar group and is involved in signaling and receptors
Vitamin A (retinol)
146
What are the functions of vitamin A?
(1) Vision
(2) Regulating Cell Differentiation
(3) Maintenance of Healthy Epithelial Tissues via the epithelial tissue differentiation.
(4) Reproduction and Growth
147
In the eye- vitamin A combines with opsin protein to form the visual pigment known as "____________"
rhodopsin
148
How does vitamin A help in vision?
In the eye- vitamin A combines with opsin protein to form the visual pigment rhodopsin which further converts light energy into nerve impulses that are sent to the brain.
149
This is the process in which immature cells change to specialized cells with function.
Cell Differentiation
150
What happens to the epithelial tissue when there is a lack of vitamin A?
Lack of vitamin A causes such surfaces to become drier and harder than normal.
151
How does vitamin A help in reproduction and growth?
In men, vitamin A participates in sperm development. In women, normal fetal development during pregnancy requires vitamin A.
152
Deficiency of Vitamin A can lead to what?
Produces night blindness because the retina and cornea dry out
153
This is known as the sunshine vitamin which controls correct ratio of Ca and P for bone mineralization (hardening) and promotes Ca and P absorption in intestine
Vitamin D
154
What are the two forms of vitamin D?
Vitamin D2 (ergocalciferol) and D3 (cholecalciferol)
155
Vitamin D is synthesized by what?
Synthesized from 7-dehydrocholesterol by UV light from sun
156
Deficiency of Vitamin D can lead to what?
Rickets in children: prevalent in densely settled urban environments
Bone disease, restlessness, slow growth
157
What are the four forms of vitamin E
alpha beta gamma delta Vitamin E
158
This is the most active biological active form of Vitamin E in humans
Alpha-tocopherol
159
This is main form in vitamin E rich foods
Gamma-tocopherol
160
What is the primary function of Vitamin E?
Primary function: Antioxidant – acts as a free radical scavenger. Prevents the oxidation of polyunsaturated fatty acid (PUFA)in membrane lipids.
161
What are the two major forms of Vitamin K?
K1 (phylloquinone) and K2 (menaquinone)
162
This form of vitamin K is found in green leafy vegetables
K1 (phylloquinone)
163
This form of vitamin K is found in fish oils and meat, eggs
K2 (menaquinone)
164
K2 (menaquinone) is synthesized by what
by bacteria that grow in the colon
165
What is the dietary need supply of vitamin k?
Dietary need supply: ~1/2 synthesized by intestinal bacteria and 1/2 obtained from diet
166
What is the function of Vitamin K?
Active in the formation of proteins involved in regulating blood clotting and is needed for the synthesis of prothrombin
167
This is a vitamin K-dependent protein directly involved with blood clotting.
Prothrombin
168
This is another protein that requires vitamin K to produce healthy bone tissue.
Osteocalcin
169
Deficiency of Vitamin D can lead to what?
(1) Vitamin K deficiency can contribute to significant bleeding,
(20 poor bone development, osteoporosis,
(3) increased risk of cardiovascular disease
