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Biochemistry > Module 07: Vitamins (Stoker) > Flashcards

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

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2
Q

In what kind of quantities are vitamins measured?

A

Micro and Milligram quantities

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3
Q

What are the two generic families of vitamins?

A

(1) Water Soluble Vitamins
(2) Fat Soluble Vitamins

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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

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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

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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

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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

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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.

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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

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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

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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

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12
Q

What carry groups carry acyl group?

A

(1) Thiamine pyrophosphate (TPP)
(2) Lipoic Acid
(3) Coenzyme A

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13
Q

This carries amino group transfer.

A

Pyridoxal Phosphate

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14
Q

This is entailed for the activation and transfer of CO2

A

Biocytin

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15
Q

This is entailed for one carbon group transfer

A

Tetrahydrofolic acid

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16
Q

This carries alkyl groups.

A

Cobamide coenzyme

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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.

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17
Q

What is the reduced form of NAD?

A

nicotinamide adenine dinucleotide phosphate (NADPH)

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18
Q

What is the oxidized form of NADPH?

A

nicotinamide adenine dinucleotide (NAD+)

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19
Q

NAD and NADP are coenzyme forms of what?

A

Niacin (Vitamin B3)

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20
Q

What are the reactions involving nicotinamide adenine dinucleotide (NAD+)

A

lactate DH, malate DH, pyruvate DH complex

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21
Q

What are the reactions involving nicotinamide adenine dinucleotide phosphate (NADPH)

A

glucose-6P-DH and NADPH in fatty acid synthase complex

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22
Q

NADP+ contains what?

A

contains a P group on 2’C of adenine ribose

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23
Q

This accepts a H-(hydride ion) and a H+ is released to the medium.

A

nicotinamide adenine dinucleotide (NAD+)

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24
Q

How does nicotinamide adenine dinucleotide (NAD+) participate in redox reactions?

A

by accepting H- ions

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25
Q

NAD + -dependent dehydrogenases are often involved in ____________.

A

catabolism

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26
Q

NADP + -dependent dehydrogenases in ______________.

A

anabolism

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27
Q

How is FADH+ (FMNH+) reduced to FADH2 (FMNH2)?

A

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.

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28
Q

This is referred to as the stable free radical, forms.

A

Semiquinone

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29
Q

FAD and FMN are coenzyme forms of what?

A

Riboflavin (Vitamin B2)

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30
Q

What are the reactions involved with flavin adenine dinucleotide (FAD)?

A

succinic acid DH, (CAC), fatty acyl CoA DH

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31
Q

What are the reactions involved with flavin adenine mononucleotide(FAM)?

A

L-amino acid oxidase

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32
Q

Riboflavin consists of what?

A

Riboflavin consists of heterocyclic ring isoalloxazine/ flavin and ribitol attached to N10

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33
Q

flavin adenine mononucleotide(FAM) is composed of what?

A

P group esterified to 5’OH of ribitol

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34
Q

flavin adenine dinucleotide (FAD) is composed of what? flavin adenine dinucleotide (FAD)?

A

has an adenosine linked by pyrophosphate bridge to riboflavin (ribitol plus flavin)

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35
Q

How is the semiquinone formed?

A

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

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36
Q

How are flavin coenzymes bounded to the enzyme (prosthetic group?

A

bound lightly or covalently

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37
Q

This is referred to as a a mitochondrial electron carrier (coenzyme Q) (n=4 to 8)

A

Ubiquinone

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38
Q

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

A

Ubiquitous

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39
Q

Ubiquitous is involved in what

A

the conversion of food into energy.

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40
Q

What is the side chain of Ubiquitous

A

The side chain consists of variable repeating isoprenoid units

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41
Q

What is the oxidized form of Ubiquitous ?

A

Ubiquinone

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42
Q

What is the reduced form of Ubiquitous?

A

ubiquinol (hydroquinone)

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43
Q

What is the reaction of Ubiquinone?

A

NADH + H+ –> CoQH2 (complex I) of the respiratory chain.

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44
Q

This is the activated form of pantothenic acid (Vitamin B5)

A

Coenzyme A

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45
Q

Coenzyme A participates in what?

A

in activation reactions through transfer of acyl groups (RC=O-)

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46
Q

What are the reactions related to coenzyme A?

A

fatty acyl CoA synthase, dihydrolipoyl transacetylase of PDH complex

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47
Q

How does coenzyme a participate in acyl group transfers?

A

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.

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48
Q

In what transfer does NAD+ participate in?

A

Hydride Transfers

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49
Q

In what transfer does FAD participate in?

A

Electron Transfers

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50
Q

What is the active form of vitamin B12?

A

adenosine is 5′-deoxyadenosylcobalamin,

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51
Q

In what transfer does adenosine is 5′-deoxyadenosylcobalamin participate in?

A

in intramolecular group transfers between adjacent carbons.

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52
Q

What is the reactive portion of coenzyme A?

A

free sulfhydryl at one end of the molecule

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53
Q

What bond can coenzyme A form with acetate and acyl?

A

Thioester Bond

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54
Q

What is the optimal integrality of Coenzyme A in the Krebs Cycle?

A

It acts as a fuel for the Krebs cycle.

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55
Q

What is the relationship between fatty acids and coenzyme A?

A

Fatty acids are activated once attached to Acyl Coenzyme A (CoA)

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56
Q

This is derived from thiamin (vitamin B1) and is used by many carboxylases and oxidative decarboxylases.

A

Thiamine Pyrophosphate, TPP

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57
Q

What are transketolases?

A

move 2 carbons at a time between sugars with keto groups

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58
Q

What is the reactive center of Thiamine Pyrophosphate, TPP?

A

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.)

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59
Q

What kind of transfer is Thiamine Pyrophosphate, TPP involved in?

A

Transfer of Aldehyde Group

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60
Q

What are the reactions involved to Thiamine Pyrophosphate, TPP?

A

pyr decarboxylase of pyr DH complex, transketolases

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61
Q

Explain the reaction behind the Thiamine Pyrophosphate, TPP?

A

(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

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62
Q

What inactivates Thiamine Pyrophosphate, TPP?

A

It requires Mg+2 for activity. TPP is inactivated by thiaminase which is found in raw fish.

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63
Q

The Pyridoxal Phosphate exists in 2 forms: what kinds?

A

(1) Pyridoxal P
(2) Pyridoxamine P

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64
Q

This is is the tightly bound coenzyme of aminotransferases / transaminase.

A

Pyridoxal 5’-phosphate (PLP)

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65
Q

In what kind of transfer is Pyridoxal 5’-phosphate (PLP) involved in?

A

They are involved in the transfer of amino groups.

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66
Q

Where is Pyridoxal 5’-phosphate (PLP) derived from?

A

Derived from Vitamin B6/ Pyridoxine, pyridoxal, pyridoxamine

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67
Q

Pyridoxal 5’-phosphate (PLP) is prosthetic group for many amino-acid-related enzymes, particularly __________

A

transaminases

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68
Q

Pyridoxal 5’-phosphate (PLP) is the derivative of what vitamin?

A

B6 - Pyridoxine

69
Q

What does Pyridoxal 5’-phosphate (PLP) form?

A

It forms an enzyme bound Schiff base intermediate that can rearrange in various ways.

70
Q

What does the rearrangement of Pyridoxal 5’-phosphate (PLP) form?

A

rearrangement forms an a keto acid and enzyme bound pyridoxamine phosphate (PMP), which forms a Schiff base with a second keto acid

71
Q

This is vitamin B7 and is involved in carboxylation reactions.

A

Biotin/ Biocytin (coenzyme)

72
Q

What kind of transfer is Biotin/ Biocytin (coenzyme) involve in?

A

Used in reactions that transfer carboxyl groups and in ATP-dependent carboxylations

73
Q

Biotin/ Biocytin (coenzyme) is composed of what?

A

Consists of imidazolone ring fused with tetrahydrothiophene linked to valeric acid.

74
Q

Where is Biotin/ Biocytin (coenzyme attached to?

A

Covalently attached to lysine in carboxylase enzyme

75
Q

Biocytin is covalently attached to lysine in carboxylase enzyme to form _____________

A

Biotin

76
Q

What reactions are involved in Biotin/ Biocytin

A

acetyl CoA carboxylase, pyruvate carboxylase, propionyl carboxylase, methylmalonyl CoA carboxylase,

76
Q

What does Biotin/ Biocytin do?

A

Accepts ATP-activated carboxyl group
and transfers it to carboxyl group acceptor

77
Q

This inhibits the synthesis of biotin and biocytin. It is also known as a protein found in raw egg white.

A

Avidin

78
Q

Tetrahydrofolate (THF) is composed of what?

A

(1) Pteridine
(2) P-aminobenzoic acid
(3) Glutamate

79
Q

These in Tetrahydrofolate (THF) can carry one carbon functional group and are in boldface.

A

N6 and N10

80
Q

How is Tetrahydrofolate formed?

A

Folate (Dihydrofolate Reductase) -Dihydrofolate (Dihydrofolate Reductase) ->Tetrahydrofolate

81
Q

Tetrahydrofolate is known as the what?

A

Primary donor of one-carbon units(formyl-CHO, methylene-CH2, methyl, methenyl-CH=,formimino-CH=NH)

82
Q

What inhibits the synthesis of Tetrahydrofolate?

A

folate antagonists such as methotrexate and sulfonamides

83
Q

This is cancer chemotherapeutic: cancer needs more thymidylate than healthy cells (- DHFR)

A

methotrexate

84
Q

This is cancer chemotherapeutic: cancer needs more ____________than healthy cells (- DHFR)

A

thymidylate

85
Q

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.

A

Trimethoprim

86
Q

What does tetrahydrofolate supply?

A

Supplies methyl group for thymidylate

87
Q

This is the largest B vitamin

A

Cobamide/Cobalamin

87
Q

Cobamide/Cobalamin is composed of what?

A

Corrin ring structure related to heme but missing one carbon in ring structure

88
Q

This is responsible for the red color of Cobamide/Cobalamin?

A

Cobalt bound in core of ring system

89
Q

What kind of enzymatic rearrangements is Cobamide/Cobalamin involved in?

A

(1) Catabolism of odd-chain fatty acids
(2) Methylation of homocysteine

90
Q

What does Coenzyme B12 (Cobalamin) contain?

A

org molecule & an essential trace element cobalt

91
Q

The 5th coordination position of cobalamin is with “____________”

A

dimethylbenzimidazole ribonucleotide

92
Q

The 6th coordination position of cobalamin is with “____________”

A

linked to 5’-deoxyadenosyl cobalamin or methyl.

93
Q

What are the active forms of Vitamin B12

A

(1) Methylcobalamin
(2) 5-deoxyadenosyl-cobalamin

94
Q

Adenosyl-Cobalamin is composed of what?

A

(1) Missing carbon
(2) Reactive Co-C Bond
(3) 2 pyrrole rings attached (Linked) Directly

95
Q

What are the two active forms of Adenosyl-Cobalamin?

A
  1. d-adenosyl cobalamin
  2. methylcobalamin/MeB12
96
Q

Adenosyl-Cobalamin participates in what?

A

Participates in racemization and methylation reactions

97
Q

This is the commercial form vitamin B12

A

cyanocobalamin

98
Q

cyanocobalamin (readily avaiable commercial form is composed of what?

A

it contains a cyano group attached to the 6th coordination position

99
Q

What happens in 5’-deoxyadenosylcobalamin

A

cyano group is replaced by 5’-deoxyadenosyl covalently attached to Co+3.

100
Q

This is the cofactor for methylmalonyl CoA mutase,

A

5’-deoxyadenosylcobalamin

101
Q

Where is cobalamin found?

A

Dietary sources are of animal origin, absent in plant foods, strict vegetarians are at risk of developing deficiency

102
Q

What does the absorption of cobalamin require?

A

IF (glycoprot) secreted by parietal cells of gastric mucosa

103
Q

How much vitamin B12 is stored in the liver that can amount to the daily metabolic requirement for 2000 days?

A

1mg (when supply is interrupted, deficiency appears after 5 years)

104
Q

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

A

Pernicious anemia

105
Q

This is a protein-bound form of lipoic acid wherein disulfides break periodically. An example of this is pyruvate dehydrogenase complex.

A

Lipoamide

106
Q

what does lipoamide contain?

A

Contains five-membered disulfide ring

107
Q

Where is lipoamide covalently bonded?

A

Covalently bound via amide to protein lysine sidechain

108
Q

Lipoamide is involved in what?

A

Covalently bound via amide to protein lysine sidechain

109
Q

lipoamide is chemically named as

A

6,8-dithiooctanoic acid or thioctic acid.

110
Q

Lipoamide exists in 2 forms, which are?

A

(1) Cyclic or Oxidized
(2) Open or Reduced form (dihydrolipoic acid)

111
Q

The S in lipoamide is in charge of what?

A

accepts and transfers acyl groups and H+ during oxidative decarboxylation of α-keto acids ex. Pyruvate

112
Q

Why don’t humans synthesize vitamins?

A

(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
Q

This can make almost everything (vitamins) given its energy and source of atoms.

A

E-coli

114
Q

What broad classifications are used to identify water soluble vitamins?

A

Coenzymes or coenzyme precursors
Energy production

115
Q

What broad classifications are used to identify fat soluble vitamins?

A

Antioxidants
Vision, bone health, coagulation

116
Q

what is vitamin B1 and what does it produce?

A

thiamin (produces TPP)

117
Q

what is vitamin B2 and what does it produce?

A

riboflavin (produces FAD, FMN)

118
Q

what is vitamin B3 and what does it produce?

A

niacin (produces NAD+, NADP+)

119
Q

what is vitamin B5 and what does it produce?

A

pantothenate (produces Coenzyme A)

120
Q

what is vitamin B6 and what does it produce?

A

pyridoxamine (produces PLP)

121
Q

what is vitamin B7 and what does it produce?

A

Biotin

122
Q

what is vitamin B9 and what does it produce?

A

folate: produces THF, THF derivatives

123
Q

what is vitamin B12 and what does it produce?

A

cobalamin (produces adenosylcobalamin, methylcobalamin)

124
Q

Deficiency in niacin can lead to what

A

Pellagra: dermatitis, diarrhea, dementia

125
Q

Where can humans synthesize nicotinamide.

A

tryptophan

126
Q

Deficiency of thiamine can result in

A

(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
Q

Deficiency of cobalamin can result in

A

(pernicious anemia): weakness, fatigue, pallor, palpitations, dizziness

128
Q

How much of the human population can be affected in the deficiency of cobalamin?

A

5-40%

129
Q

What is the function of vitamin C?

A

Functions as a cofactor in the formation of collagen and is involved in metabolism of certain amino acids

130
Q

How much vitamin C is needed by humans?

A

100 mg/day saturates all body tissues - Excess vitamin is excreted

131
Q

What are the two forms of vitamin C?

A

Reduced (RA) and oxidized form (OA)

132
Q

Vitamin C can be synthesized by what?

A

L-gluonic acid

133
Q

This is a post-translational modification that occurs to prolines within collagen.

A

Proline + O2 + -ketoglutarate + ascorbate  4-hydroxyproline + succinate + CO2 + dehydroascorbate

134
Q

In the PTM role of ascorbate, these help stabilize the collagen triple helix

A

hydroxylated prolines

135
Q

In the PTM role of ascorbate, this is known as the oxidoreductase

A

hydroxylase

136
Q

This are the two cofactors needed by hydroxylases for the synthesis of collagen

A

Fe+2 and ascorbic acid

137
Q

In the PTM role of ascorbate, this is needed to keep iron in the +2 state. It serves as a reducing agent (antioxidant)

A

ascorbic acid

138
Q

Ascorbate deficiency can lead to?

A

collagen degradation, leading to scurvy

139
Q

These are absorbed in intestine, carried via bile salts wherein most are formally built from isoprene units, as are steroids

A

Lipid Vitamins

140
Q

Lipid vitamins are composed of what

A

(1) Contain rings & long aliphatic sidechains
(2) At least one polar group in each
(3) isoprene units, as are steroids

141
Q

Preformed vitamin A are called _____________ derived from animal sources.

A

retinoids (retinol, retinal and retinoic acid

142
Q

Plants provide _________ which are precursor forms of vitamin A or provitamin A

A

carotenoids

143
Q

This is the major carotenoid which can be cleaved to two molecules of vitamin A. Present in yellow fruits and vegetables.

A

B-carotene

144
Q

B-carotene is known as a

A

nonpolar dimer

145
Q

This has 3 forms varying in terminal polar group and is involved in signaling and receptors

A

Vitamin A (retinol)

146
Q

What are the functions of vitamin A?

A

(1) Vision
(2) Regulating Cell Differentiation
(3) Maintenance of Healthy Epithelial Tissues via the epithelial tissue differentiation.
(4) Reproduction and Growth

147
Q

In the eye- vitamin A combines with opsin protein to form the visual pigment known as “____________”

A

rhodopsin

148
Q

How does vitamin A help in vision?

A

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
Q

This is the process in which immature cells change to specialized cells with function.

A

Cell Differentiation

150
Q

What happens to the epithelial tissue when there is a lack of vitamin A?

A

Lack of vitamin A causes such surfaces to become drier and harder than normal.

151
Q

How does vitamin A help in reproduction and growth?

A

In men, vitamin A participates in sperm development. In women, normal fetal development during pregnancy requires vitamin A.

152
Q

Deficiency of Vitamin A can lead to what?

A

Produces night blindness because the retina and cornea dry out

153
Q

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

A

Vitamin D

154
Q

What are the two forms of vitamin D?

A

Vitamin D2 (ergocalciferol) and D3 (cholecalciferol)

155
Q

Vitamin D is synthesized by what?

A

Synthesized from 7-dehydrocholesterol by UV light from sun

156
Q

Deficiency of Vitamin D can lead to what?

A

Rickets in children: prevalent in densely settled urban environments
Bone disease, restlessness, slow growth

157
Q

What are the four forms of vitamin E

A

alpha beta gamma delta Vitamin E

158
Q

This is the most active biological active form of Vitamin E in humans

A

Alpha-tocopherol

159
Q

This is main form in vitamin E rich foods

A

Gamma-tocopherol

160
Q

What is the primary function of Vitamin E?

A

Primary function: Antioxidant – acts as a free radical scavenger. Prevents the oxidation of polyunsaturated fatty acid (PUFA)in membrane lipids.

161
Q

What are the two major forms of Vitamin K?

A

K1 (phylloquinone) and K2 (menaquinone)

162
Q

This form of vitamin K is found in green leafy vegetables

A

K1 (phylloquinone)

163
Q

This form of vitamin K is found in fish oils and meat, eggs

A

K2 (menaquinone)

164
Q

K2 (menaquinone) is synthesized by what

A

by bacteria that grow in the colon

165
Q

What is the dietary need supply of vitamin k?

A

Dietary need supply: ~1/2 synthesized by intestinal bacteria and 1/2 obtained from diet

166
Q

What is the function of Vitamin K?

A

Active in the formation of proteins involved in regulating blood clotting and is needed for the synthesis of prothrombin

167
Q

This is a vitamin K-dependent protein directly involved with blood clotting.

A

Prothrombin

168
Q

This is another protein that requires vitamin K to produce healthy bone tissue.

A

Osteocalcin

169
Q

Deficiency of Vitamin D can lead to what?

A

(1) Vitamin K deficiency can contribute to significant bleeding,
(20 poor bone development, osteoporosis,
(3) increased risk of cardiovascular disease

Biochemistry (16 decks)

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