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Vitamins Flashcards

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1
Q

Name the fat soluble and water soluble vitamins

A

Water soluble: Vitamin B, C

Fat soluble: Vitamin D, E, A, K

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2
Q

Name all the vitamin Bs and Hs

A

B1: Thiamin
B2: Riboflavin
B3: Niacin
B5: Pantothenic acid
B6: Pyridoxal, pyridoxamine, pyridoxine
(active form: pyridoxal-5’-phosphate)
B9: Folic acid, folate
B12: Cobalamine

H: Biotin

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3
Q

Vitamin bioavailability is affected by? There’s 3

A

Absorption, transport, conversion

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4
Q

How is vitamin bioavailability affected by absorption?

A

Vitamins must be absorbed by the body in order to perform their function.
Approx. 40-90% of vitamins are absorbed in the small intestine.
Fat-soluble vitamins require fat in the diet to be absorbed.
Water-soluble vitamins may require transport molecules or specific molecules in the GI tract.

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5
Q

How is vitamin bioavailability affected by transport?

A

Water-soluble vitamins: blood proteins
Fat-soluble vitamins: chylomicrons

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6
Q

How is vitamin bioavailability affected by conversion?

A

Some vitamins are absorbed in inactive form (provitamin or vitamin precursor) that must be converted into active forms by the body

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7
Q

Where is niacin absorbed?

A

The stomach, when digested food release vitamins

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8
Q

What does bile released by the gallbladder do to help vitamin absorption?

A

Bile emulsifies fat and helps absorb fat-soluble vitamins (DEAK)

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9
Q

How are fat-soluble vitamins absorbed into the blood from the small intestine?

A

Fat-soluble vitamins are incorporated into micelles and then absorbed into mucosal cells by simple diffusion.
Fat-soluble vitamins are then packaged in chylomicrons, which enter the lymph before passing into the blood.

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10
Q

What is a cofactor?

A

Cofactor is a non-protein chemical compound that is bound to a protein and is required for the proteins biological activity. Cofactors cannot be synthesized by mammals.

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11
Q

Types of cofactor

A

Essential ions: activator ions (loosely bound) and metal ions of metalloenzymes (tightly bound)

Coenzyme: co-substrates (loosely bound) and prosthetic groups (tightly bound)

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12
Q

Vitamins form a part of the ___ that enable enzymes either to ___ compounds or to ___compounds (catabolic and anabolic process)

A

Vitamins form a part of the coenzymes that enable enzymes either to synthesis compounds or to dismantle compounds (catabolic and anabolic process)

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13
Q

The water-soluble vitamins (Vit ___ complexes), are ___ precursor of several ___.

A

The water-soluble vitamins (Vit B complexes), are metabolically precursor of several coenzymes.

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14
Q

What are the 3 classes of vitamin-derived coenzymes used to carry electrons.

A
  1. Ascorbic acid (Vitamin C)
  2. Nicotinamide coenzymes (Vitamin B3-niacin)
  3. Flavin coenzymes (Vitamin B2-riboflavin)
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15
Q

Active form of ascorbic acid (vitamin C)

A

Ascorbate

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16
Q

Function of ascorbic acid (vit C)? Have 5

A
  1. Antioxidant: inactivates free oxygen radicals and protects (& regenerate) other antioxidants vitamin A and E
  2. Essential for iron absorption, reducing Fe3+ to Fe2+
  3. Coenzyme in hydroxylation reactions - collagen synthesis (required for proline & lysine hydroxylation)
  4. Required for dopamine β-hydroxylase (essential enzyme of norepinephrine and epinephrine synthesis)
  5. For bile acid synthesis (fat-soluble vit absorption) and for tyrosine degradation
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17
Q

What are the 2 different forms that ascorbic acid exist in and the inactive form of ascorbic acid? Which one predominates in the plasma and tissue and at what ratio?

A

Reduced form: L-ascorbic acid
Oxidized form: L-dehydroascorbic acid

Inactive form (hydrated form): L-diketogulonic acid

The reduced form predominates at a ratio of about 15:1 of the oxidized form

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18
Q

Mechanism of recycling ascorbic acid:

After ascorbic acid is used to reduce a substance, the ascorbic acid is ___ to ___ (DHA) which can be ___ back to ascorbic acid either by ___ or by the actions of ___ (GSH).

*What is the enzyme used to catalyze the reaction of ascorbic acid to DHA?

A

Mechanism of recycling ascorbic acid:

After ascorbic acid is used to reduce a substance, the ascorbic acid is oxidized to dehydroascorbic acid (DHA) which can be reduced back to ascorbic acid either by NADH or by the actions of glutathione (GSH).

Ascorbate oxidase is used to oxidize ascorbic acid to ascorbate radical intermediate then to dehydroascorbic acid.

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19
Q

Vitamin B3 is also known as Niacin. What are the 2 molecules that fall under the name Niacin?
Also, both of the Niacin can act as precursor of nicotinamide coenzymes. Name the 2 coenzymes.

A

Nicotinamide (amide functional group) and nicotinic acid (carboxylic acid functional group) are both called Niacin

Both act as a precursor of nicotinamide coenzymes Nicotinamide Adenine Dinucleotide (NAD) and Nicotinamide Adenine Dinucleotide-2’-Phosphate (NADP+)

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20
Q

What are the 2 differences between NAD+/NADH and NADP+/NADPH

A

NAD+/NADH - regulator of cellular energy metabolism of glycolysis and mitochondrial oxidative phosphorylation
NADP+/NADPH - involved in maintaining redox balance and supporting the biosynthesis of fatty acids and nucleic acids

NAD+/NADH - primarily involved in catabolic reactions (reactions that break down molecules to release energy)
NADP+/NADPH - primarily involved in anabolic reactions (reactions that consume energy in order to build up/synthesize larger molecules

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21
Q

NAD & NADP undergo ___ reduction of the nicotinamide ring.
reduction of NAD+ or NADP+ converts the ___ (6-membered structure) ring of the nicotinamide ___ form (fixed positive charge on the ring nitrogen) to the ___ form (no charge on the ring nitrogen)

A

NAD & NADP undergo reversible reduction of the nicotinamide ring.
reduction of NAD+ or NADP+ converts the benzenoid (6-membered structure) ring of the nicotinamide moiety form (fixed positive charge on the ring nitrogen) to the quinonoid form (no charge on the ring nitrogen)

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22
Q

What is used to determine which niacin coenzyme (NAD/NADP) is involved in a reaction?

A

By comparing wavelength of light absorbed. The reduced nucleotides (NADH) absorbs light at 340nm while the oxidized forms do not.

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23
Q

How does NAD+/NADP+ and NADH/NADPH work?

Study These Flashcards
A

NAD+/NADP+ accepts a hydride ion from a reduced substrate while NADH/NADPH donates a hydride ion to an oxidized substrate

24
Q

What does niacin deficiency affect and what disease does it cause?

Study These Flashcards
A

Niacin deficiency (vitamin B3 deficiency) affects all NAD(P)-dependent dehydrogenase, causing human disease pellagra

25
How do mammals obtain riboflavin (Vitamin B2)?
Riboflavin is synthesized by bacteria protists, fungi, plants and some animals. Mammals may obtain riboflavin from food
26
Structure of riboflavin (Vitamin B2)
Riboflavin consist of the 5-carbon alcohol ribitol linked to the N-10 atom of a heterocyclic ring system, isoalloxazine
27
What reaction is riboflavin (Vitamin B2) involved in?
1. Redox reaction in TCA cycle 2. Respiratory chain in mitochondria 3. Oxidation of fatty acids 4. Metabolism of amino acids
28
Riboflavin is the precursor of the ___ coenzymes FMN (___ ___) and FAD (___ ___ ___). ___ use flavin to carry out ___-___ reactions.
Riboflavin is the precursor of the flavin coenzymes FMN (Flavin Mononucleotide) and FAD (Flavin Adenine Dinucleotide). Flavoenzymes use flavin to carry out oxidation-reduction reactions.
29
What does flavins and nicotinamide coenzymes have in common and what is distinctive between the flavin and nicotinamide coenzymes?
Flavin and nicotinamide coenzymes undergo two-electron oxidation and reduction reaction. Flavins are distinctive in having a stable one-electron-reduced species, a semiquinone free radical.
30
Flavin can form a semiquinone free radical. How is this free radical detected? What colour do they appear as?)
The free radical can be detected spectrophotometrically. Oxidized FAD (Flavin Adenine Dinucleotide) and FMN (Flavin Mononucleotide) are bright yellow. Fully reduced flavins are colourless. The semiquinone free radical intermediate is either red or blue, depending on the pH.
31
The vitamin B6 family of water-soluble vitamins consist of 3 closely related molecules. Name the 3 molecules and the difference between the 3 molecules.
Pyridoxine, Pyridoxal, Pyridoxamine The molecules differ only in the state of oxidation or amination of the carbon bound to position 4 of the pyridine ring Pyridoxine: alcohol group (-OH bound to carbon bound to C4 of the ring) Pyridoxal: carbonyl group (=O bound to carbon bound to C4 of the ring) Pyridoxamine: amine group ( -NH3+ bound to carbon bound to C4 of the ring)
32
Pyridoxal 5'-Phosphate (PLP) are ___ group for many enzymes that catalyze a variety of reactions like ___, ___, ___
Pyridoxal 5'-Phosphate (PLP) are prosthetic group for many enzymes that catalyze a variety of reactions like transamination, decarboxylation, racemization
33
In PLP (pyridoxal 5'-Phosphate)-dependent enzymes, the carbonyl group of the ___ group is bound as the ___ ___ (imine) to the ___-___ group (amino group bound to C5 of lysine) of a lysine residue at the ___ site. This enzyme-coenzyme ___ ___ is referred as an internal ___.
In PLP (pyridoxal 5'-Phosphate)-dependent enzymes, the carbonyl group of the prosthetic group is bound as the Schiff base (imine) to the ε-amino group (amino group bound to C5 of lysine) of a lysine residue at the active site. This enzyme-coenzyme Schiff base is referred as an internal aldimine.
34
What is the initial step in all PLP-dependent enzymatic reactions with amino acids?
The initial step is the linkage of PLP to the α-amino group of the amino acid (external aldimine) PLP: Pyridoxal 5'-Phosphate
35
Structure of cobalamin (Vitamin B12)
Structure of vitamin B12 includes a corrine ring system that resembles the porphyrin system of heme.
36
Name the 2 uses of cobalamin (vitamin B12).
1. It is used in isomerization reactions -- for the shifting of hydrogen between carbon atoms 2. Acts as a methyl group carrier, accepting the carbon from the tetrahydrofolate derivates
37
What happens in cobalamin deficiency?
Pernicious anemia - decrease in the production of blood cell by bone marrow which may lead to a potentially fatal disease.
38
What are the 2 reactions that Biotin (Vitamin H),a prosthetic group for enzymes, catalyzes? Also, what is the molecule that biotin is a specialized carrier of?
1. Carboxyl group transfer reactions 2. ATP-dependent carboxylation reactions Biotin is a specialized carrier of one-carbon groups in their most oxidized form - CO2
39
What are the 3 main components of Vitamin B9 (folic acid, folate)?
1. Pterin (2-amino-4-oxopteridine) 2. P-aminobenzoic acid moeity (PABA) 3. Glutamate residue
40
What are the 2 ways in which vitamin B9 and its coenzyme forms (tetrahydrofolate) differ in?
1. Tetrahydrofolate are reduced compounds of folate (5, 6, 7, 8-tetrahydropterins) 2. Tetrahydrofolate are modified by the addition of glutamate residues bound to one another through γ-glutamyl (gamma-glutamyl) amide linkages
41
Name the structure of Thiamin (vitamin B1), its conenzyme form, and the reaction thiamin is involved in.
Structure: pyrimidine ring and a positively charged thiazolium ring Coenzyme form: thiamine pyrophosphate (TPP) or thiamine diphosphate (TDP) Reaction: ATP-dependent phosphorylation
42
What is Pantothenic acid (vitamin B5) a precursor of? Also, name the role of vitamin B5 in Acyl Carrier Protein (ACP).
Vitamin B5 (Pantothenic acid) is a precursor of coenzyme A (CoA) and the prosthetic group of Acyl Carrier Protein (ACP) domain in fatty acid synthase
43
Which part of the Coenzyme A creates the pantothenic arc?
The panthetonic acid residue
44
What are the 3 common features of fat-soluble vitamins
1. Soluble in nonpolar organic solvents 2. All of them are isoprenoid compounds consisting of multiple isoprene units and an aromatic ring 3. Have common structures but diverse functions
45
What are the 3 active forms of Retinol (vitamin A)? Also, what are they collectively known as?
1. All-trans-retinol (alcohol) 2. All-trans-retinal (aldehyde) 3. All-trans-retinoic acid (carboxylic acid) Collectively known as retinoids
46
How is retinol (vitamin A) obtained?
Consumed as esterified retinol or biosynthesized from β-carotene (plant isoprenoid)
47
Retinol, retinal, and retinoic acid undergo oxidation to shift between the different active forms. Which oxidation reactions are reversible and irreversible?
Reversible: oxidation of retinol to retinal (alcohol to aldehyde: -OH to =O) Irreversible: oxidation of retinol or retinal to retinoic acid
48
What are the 3 major roles of retinol (vitamin A)?
1. Promoting vision 2. Participating in protein synthesis and cell differentiation 3. Supporting reproduction and growth
49
Vitamin D is a collective name for a group of related lipids. Name the 2 lipids and how they are formed.
Cholecalciferol - vitamin D3: formed nonenzymatically in the skin from the steroid-7-dehydrocholesterol (when exposed to sufficient sunlight) Ergocalciferol - vitamin D2: a commercial product formed by UV irradiation of the ergosterol of yeast
50
Cholecalciferol (Vitamin D3) is not biologically active. Name the active form of vitamin D3 and its function.
Vitamin D3 is converted to its active form 1,25-dihydroxycholecalciferol, a hormone that regulates calcium uptake in the intestines and calcium levels in the bone
51
Function of Ergocalciferol (vitamin D2).
Vitamin D2 is structurally similar to Vitamin D3 and has the same biological effect, but vitamin D2 is commonly added to milk and butter as a dietary supplement
52
Describe the structure of α-tocopherol (Vitamin E) and how its phenol group helps maintain its stability.
Vitamin E has a bicyclic oxygen-containing ring system with a hydrophobic side chain. The phenol group of Vitamin E can undergo oxidation to a stable free radical.
53
Function of Vitamin E (α-tocopherol).
Vitamin E is believed to function as a reducing agent that scavenges oxygen and free radicals.
54
Cause and effect of vitamin E (α-tocopherol) deficiency.
The deficiency of vitamin E is almost always caused by genetic defects in the absorption of fat molecules. Deficiency in vitamin E may lead to fragile red blood cells and neurological damage.
55
Vitamin K was originally discovered as a lipid-soluble substance involved in blood coagulation. Name the 3 types of Vitamin K and where and how it is synthesized
Vitamin K1 - Phylloquinone: plant version of vitamin K, used by plant in photosynthesis Vitamin K2 - Menaquinone-7: bacterial product and can be produced in humans from menadione (by adding hydrocarbon chain to menadione) Vitamin K3 - Menadione: synthetic compound that can be converted into the active forms of vitamin K, readily absorbed but toxic.
56
What are the 3 functions of vitamin K?
1. Required as enzyme cofactor in the synthesis of γ-carboxyglutamic acid, important for function of a lot of proteins (clotting factors) 2. The reduced form of vitamin K acts as a coenzyme for the carboxylase that produces the modified glutamate side chain 3. Vitamin K Epoxide Reductase (VKOR) Catalyzes the formation of the active hydroquinone form of vitamin K and the regeneration of the quinone

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