Module 07: Vitamins (Stoker) Flashcards
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.
Vitamins
In what kind of quantities are vitamins measured?
Micro and Milligram quantities
What are the two generic families of vitamins?
(1) Water Soluble Vitamins
(2) Fat Soluble Vitamins
What is the difference between water soluble vitamins and fat soluble vitamins in terms of absorption?
Water soluble vitamins: Directly into the blood
Fat soluble vitamins: First enter into the lymph system
What is the difference between water soluble vitamins and fat soluble vitamins in terms of transport?
Water soluble vitamins: They travel without carriers
Fat soluble vitamins: They entail (require) protein carriers
What is the difference between water soluble vitamins and fat soluble vitamins in terms of storage?
Water soluble vitamins: They circulate in water-filled parts of the body
Fat soluble vitamins: They are formed in the cells associated with fat
What is the difference between water soluble vitamins and fat soluble vitamins in terms of excretion?
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
What is the difference between water soluble vitamins and fat soluble vitamins in terms of toxicity?
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.
What is the difference between water soluble vitamins and fat soluble vitamins in terms of dosage frequency?
Water soluble vitamins: needed frequent doses
Fat soluble vitamins: needed in periodic doses
What is the difference between water soluble vitamins and fat soluble vitamins in terms of coenzymes?
Water soluble vitamins: function as coenzymes
Fat soluble vitamins: do not function as coenzymes
What enzymes participate in the transfer of H+ and e-?
(1) nicotinamide adenine dinucleotide (NAD+) and Nicotinamide adenine dinucleotide phosphate (NADP)
(2) Flavin mononucleotide (FMN) and flavin dinucleotide (FAD)
(3) Coenzyme Q
What carry groups carry acyl group?
(1) Thiamine pyrophosphate (TPP)
(2) Lipoic Acid
(3) Coenzyme A
This carries amino group transfer.
Pyridoxal Phosphate
This is entailed for the activation and transfer of CO2
Biocytin
This is entailed for one carbon group transfer
Tetrahydrofolic acid
This carries alkyl groups.
Cobamide coenzyme
How is NADH reduced to NADPH?
(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.
What is the reduced form of NAD?
nicotinamide adenine dinucleotide phosphate (NADPH)
What is the oxidized form of NADPH?
nicotinamide adenine dinucleotide (NAD+)
NAD and NADP are coenzyme forms of what?
Niacin (Vitamin B3)
What are the reactions involving nicotinamide adenine dinucleotide (NAD+)
lactate DH, malate DH, pyruvate DH complex
What are the reactions involving nicotinamide adenine dinucleotide phosphate (NADPH)
glucose-6P-DH and NADPH in fatty acid synthase complex
NADP+ contains what?
contains a P group on 2’C of adenine ribose
This accepts a H-(hydride ion) and a H+ is released to the medium.
nicotinamide adenine dinucleotide (NAD+)
How does nicotinamide adenine dinucleotide (NAD+) participate in redox reactions?
by accepting H- ions
NAD + -dependent dehydrogenases are often involved in ____________.
catabolism
NADP + -dependent dehydrogenases in ______________.
anabolism
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.
This is referred to as the stable free radical, forms.
Semiquinone
FAD and FMN are coenzyme forms of what?
Riboflavin (Vitamin B2)
What are the reactions involved with flavin adenine dinucleotide (FAD)?
succinic acid DH, (CAC), fatty acyl CoA DH
What are the reactions involved with flavin adenine mononucleotide(FAM)?
L-amino acid oxidase
Riboflavin consists of what?
Riboflavin consists of heterocyclic ring isoalloxazine/ flavin and ribitol attached to N10
flavin adenine mononucleotide(FAM) is composed of what?
P group esterified to 5’OH of ribitol
flavin adenine dinucleotide (FAD) is composed of what? flavin adenine dinucleotide (FAD)?
has an adenosine linked by pyrophosphate bridge to riboflavin (ribitol plus flavin)
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
How are flavin coenzymes bounded to the enzyme (prosthetic group?
bound lightly or covalently
This is referred to as a a mitochondrial electron carrier (coenzyme Q) (n=4 to 8)
Ubiquinone
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
Ubiquitous is involved in what
the conversion of food into energy.
What is the side chain of Ubiquitous
The side chain consists of variable repeating isoprenoid units
What is the oxidized form of Ubiquitous ?
Ubiquinone
What is the reduced form of Ubiquitous?
ubiquinol (hydroquinone)
What is the reaction of Ubiquinone?
NADH + H+ –> CoQH2 (complex I) of the respiratory chain.
This is the activated form of pantothenic acid (Vitamin B5)
Coenzyme A
Coenzyme A participates in what?
in activation reactions through transfer of acyl groups (RC=O-)
What are the reactions related to coenzyme A?
fatty acyl CoA synthase, dihydrolipoyl transacetylase of PDH complex
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.
In what transfer does NAD+ participate in?
Hydride Transfers
In what transfer does FAD participate in?
Electron Transfers
What is the active form of vitamin B12?
adenosine is 5′-deoxyadenosylcobalamin,
In what transfer does adenosine is 5′-deoxyadenosylcobalamin participate in?
in intramolecular group transfers between adjacent carbons.
What is the reactive portion of coenzyme A?
free sulfhydryl at one end of the molecule
What bond can coenzyme A form with acetate and acyl?
Thioester Bond
What is the optimal integrality of Coenzyme A in the Krebs Cycle?
It acts as a fuel for the Krebs cycle.
What is the relationship between fatty acids and coenzyme A?
Fatty acids are activated once attached to Acyl Coenzyme A (CoA)
This is derived from thiamin (vitamin B1) and is used by many carboxylases and oxidative decarboxylases.
Thiamine Pyrophosphate, TPP
What are transketolases?
move 2 carbons at a time between sugars with keto groups
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.)
What kind of transfer is Thiamine Pyrophosphate, TPP involved in?
Transfer of Aldehyde Group
What are the reactions involved to Thiamine Pyrophosphate, TPP?
pyr decarboxylase of pyr DH complex, transketolases
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
What inactivates Thiamine Pyrophosphate, TPP?
It requires Mg+2 for activity. TPP is inactivated by thiaminase which is found in raw fish.
The Pyridoxal Phosphate exists in 2 forms: what kinds?
(1) Pyridoxal P
(2) Pyridoxamine P
This is is the tightly bound coenzyme of aminotransferases / transaminase.
Pyridoxal 5’-phosphate (PLP)
In what kind of transfer is Pyridoxal 5’-phosphate (PLP) involved in?
They are involved in the transfer of amino groups.
Where is Pyridoxal 5’-phosphate (PLP) derived from?
Derived from Vitamin B6/ Pyridoxine, pyridoxal, pyridoxamine
Pyridoxal 5’-phosphate (PLP) is prosthetic group for many amino-acid-related enzymes, particularly __________
transaminases
Pyridoxal 5’-phosphate (PLP) is the derivative of what vitamin?
B6 - Pyridoxine
What does Pyridoxal 5’-phosphate (PLP) form?
It forms an enzyme bound Schiff base intermediate that can rearrange in various ways.
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
This is vitamin B7 and is involved in carboxylation reactions.
Biotin/ Biocytin (coenzyme)
What kind of transfer is Biotin/ Biocytin (coenzyme) involve in?
Used in reactions that transfer carboxyl groups and in ATP-dependent carboxylations
Biotin/ Biocytin (coenzyme) is composed of what?
Consists of imidazolone ring fused with tetrahydrothiophene linked to valeric acid.
Where is Biotin/ Biocytin (coenzyme attached to?
Covalently attached to lysine in carboxylase enzyme
Biocytin is covalently attached to lysine in carboxylase enzyme to form _____________
Biotin
What reactions are involved in Biotin/ Biocytin
acetyl CoA carboxylase, pyruvate carboxylase, propionyl carboxylase, methylmalonyl CoA carboxylase,
What does Biotin/ Biocytin do?
Accepts ATP-activated carboxyl group
and transfers it to carboxyl group acceptor
This inhibits the synthesis of biotin and biocytin. It is also known as a protein found in raw egg white.
Avidin
Tetrahydrofolate (THF) is composed of what?
(1) Pteridine
(2) P-aminobenzoic acid
(3) Glutamate
These in Tetrahydrofolate (THF) can carry one carbon functional group and are in boldface.
N6 and N10
How is Tetrahydrofolate formed?
Folate (Dihydrofolate Reductase) -Dihydrofolate (Dihydrofolate Reductase) ->Tetrahydrofolate
Tetrahydrofolate is known as the what?
Primary donor of one-carbon units(formyl-CHO, methylene-CH2, methyl, methenyl-CH=,formimino-CH=NH)
What inhibits the synthesis of Tetrahydrofolate?
folate antagonists such as methotrexate and sulfonamides
This is cancer chemotherapeutic: cancer needs more thymidylate than healthy cells (- DHFR)
methotrexate
This is cancer chemotherapeutic: cancer needs more ____________than healthy cells (- DHFR)
thymidylate
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
What does tetrahydrofolate supply?
Supplies methyl group for thymidylate
This is the largest B vitamin
Cobamide/Cobalamin
Cobamide/Cobalamin is composed of what?
Corrin ring structure related to heme but missing one carbon in ring structure
This is responsible for the red color of Cobamide/Cobalamin?
Cobalt bound in core of ring system
What kind of enzymatic rearrangements is Cobamide/Cobalamin involved in?
(1) Catabolism of odd-chain fatty acids
(2) Methylation of homocysteine
What does Coenzyme B12 (Cobalamin) contain?
org molecule & an essential trace element cobalt
The 5th coordination position of cobalamin is with “____________”
dimethylbenzimidazole ribonucleotide
The 6th coordination position of cobalamin is with “____________”
linked to 5’-deoxyadenosyl cobalamin or methyl.
What are the active forms of Vitamin B12
(1) Methylcobalamin
(2) 5-deoxyadenosyl-cobalamin
Adenosyl-Cobalamin is composed of what?
(1) Missing carbon
(2) Reactive Co-C Bond
(3) 2 pyrrole rings attached (Linked) Directly
What are the two active forms of Adenosyl-Cobalamin?
- d-adenosyl cobalamin
- methylcobalamin/MeB12
Adenosyl-Cobalamin participates in what?
Participates in racemization and methylation reactions
This is the commercial form vitamin B12
cyanocobalamin
cyanocobalamin (readily avaiable commercial form is composed of what?
it contains a cyano group attached to the 6th coordination position
What happens in 5’-deoxyadenosylcobalamin
cyano group is replaced by 5’-deoxyadenosyl covalently attached to Co+3.
This is the cofactor for methylmalonyl CoA mutase,
5’-deoxyadenosylcobalamin
Where is cobalamin found?
Dietary sources are of animal origin, absent in plant foods, strict vegetarians are at risk of developing deficiency
What does the absorption of cobalamin require?
IF (glycoprot) secreted by parietal cells of gastric mucosa
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)
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
This is a protein-bound form of lipoic acid wherein disulfides break periodically. An example of this is pyruvate dehydrogenase complex.
Lipoamide
what does lipoamide contain?
Contains five-membered disulfide ring
Where is lipoamide covalently bonded?
Covalently bound via amide to protein lysine sidechain
Lipoamide is involved in what?
Covalently bound via amide to protein lysine sidechain
lipoamide is chemically named as
6,8-dithiooctanoic acid or thioctic acid.
Lipoamide exists in 2 forms, which are?
(1) Cyclic or Oxidized
(2) Open or Reduced form (dihydrolipoic acid)
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
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
This can make almost everything (vitamins) given its energy and source of atoms.
E-coli
What broad classifications are used to identify water soluble vitamins?
Coenzymes or coenzyme precursors
Energy production
What broad classifications are used to identify fat soluble vitamins?
Antioxidants
Vision, bone health, coagulation
what is vitamin B1 and what does it produce?
thiamin (produces TPP)
what is vitamin B2 and what does it produce?
riboflavin (produces FAD, FMN)
what is vitamin B3 and what does it produce?
niacin (produces NAD+, NADP+)
what is vitamin B5 and what does it produce?
pantothenate (produces Coenzyme A)
what is vitamin B6 and what does it produce?
pyridoxamine (produces PLP)
what is vitamin B7 and what does it produce?
Biotin
what is vitamin B9 and what does it produce?
folate: produces THF, THF derivatives
what is vitamin B12 and what does it produce?
cobalamin (produces adenosylcobalamin, methylcobalamin)
Deficiency in niacin can lead to what
Pellagra: dermatitis, diarrhea, dementia
Where can humans synthesize nicotinamide.
tryptophan
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
Deficiency of cobalamin can result in
(pernicious anemia): weakness, fatigue, pallor, palpitations, dizziness
How much of the human population can be affected in the deficiency of cobalamin?
5-40%
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
How much vitamin C is needed by humans?
100 mg/day saturates all body tissues - Excess vitamin is excreted
What are the two forms of vitamin C?
Reduced (RA) and oxidized form (OA)
Vitamin C can be synthesized by what?
L-gluonic acid
This is a post-translational modification that occurs to prolines within collagen.
Proline + O2 + -ketoglutarate + ascorbate 4-hydroxyproline + succinate + CO2 + dehydroascorbate
In the PTM role of ascorbate, these help stabilize the collagen triple helix
hydroxylated prolines
In the PTM role of ascorbate, this is known as the oxidoreductase
hydroxylase
This are the two cofactors needed by hydroxylases for the synthesis of collagen
Fe+2 and ascorbic acid
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
Ascorbate deficiency can lead to?
collagen degradation, leading to scurvy
These are absorbed in intestine, carried via bile salts wherein most are formally built from isoprene units, as are steroids
Lipid Vitamins
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
Preformed vitamin A are called _____________ derived from animal sources.
retinoids (retinol, retinal and retinoic acid
Plants provide _________ which are precursor forms of vitamin A or provitamin A
carotenoids
This is the major carotenoid which can be cleaved to two molecules of vitamin A. Present in yellow fruits and vegetables.
B-carotene
B-carotene is known as a
nonpolar dimer
This has 3 forms varying in terminal polar group and is involved in signaling and receptors
Vitamin A (retinol)
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
In the eye- vitamin A combines with opsin protein to form the visual pigment known as “____________”
rhodopsin
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.
This is the process in which immature cells change to specialized cells with function.
Cell Differentiation
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.
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.
Deficiency of Vitamin A can lead to what?
Produces night blindness because the retina and cornea dry out
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
What are the two forms of vitamin D?
Vitamin D2 (ergocalciferol) and D3 (cholecalciferol)
Vitamin D is synthesized by what?
Synthesized from 7-dehydrocholesterol by UV light from sun
Deficiency of Vitamin D can lead to what?
Rickets in children: prevalent in densely settled urban environments
Bone disease, restlessness, slow growth
What are the four forms of vitamin E
alpha beta gamma delta Vitamin E
This is the most active biological active form of Vitamin E in humans
Alpha-tocopherol
This is main form in vitamin E rich foods
Gamma-tocopherol
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.
What are the two major forms of Vitamin K?
K1 (phylloquinone) and K2 (menaquinone)
This form of vitamin K is found in green leafy vegetables
K1 (phylloquinone)
This form of vitamin K is found in fish oils and meat, eggs
K2 (menaquinone)
K2 (menaquinone) is synthesized by what
by bacteria that grow in the colon
What is the dietary need supply of vitamin k?
Dietary need supply: ~1/2 synthesized by intestinal bacteria and 1/2 obtained from diet
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
This is a vitamin K-dependent protein directly involved with blood clotting.
Prothrombin
This is another protein that requires vitamin K to produce healthy bone tissue.
Osteocalcin
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
