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90 Cards in this Set

  • Front
  • Back
Energy metabolism
1)Thiamine (B1)
2)Riboflavin (B2)
3)Niacin (B3)
5)Pantothenic acid (B5)
Amino Acid metabolism

- pyridoxine
- pyridoxal
- pyridoxamine
RBC/Neural development
- Folic acid
- Cobalamine (B12)
Collagen synthesis
- ascorbic acid
Vitamin A
- vision
- epithelial tissue
- growth in children
Vitamin D
- bone mineralization
- blood Ca++ regulation
Vitamin E
Vitamin K
clotting factor
B1 deficiency
- ↓ ATP
- IV glucose can precipitate in alcoholics
where is transketolase found?
- ribose 5-P --> xylulose 5-P to sedoheptulose 7-P --> glyceraldehyde 3-P
- cofactor in succinate dehydrogenase in TCA
- flavin adenine dinucleotide
- ETC, accepts 2 e- from NADH in NADH deH rxn
- flavin mononucleotide
how is niacin made endogenously?
- excess tryptophan produces 10% of RDA
what type of reaction does it facilitate?
- redox involving a hydride ion transfer
Poor man's lipitor
- 100x RDA treats type IIb hyperlipoproteinemia
Panothenic acid (B5)active form
- coA
- part of fatty acid synthase complex
B6 active form
- pyridoxal phosphate
Functions of B6
- transamination
- deamination
- decarboxylation
- condensation reactions
- ALA synthase
- synthesis of GABA, 5HT, NE
Causes of B6 deficiency
- isoniazid (TB drug)
- alcoholics, infants with deficient formula
- women on OCT
What is the toxic dose?
- neurological symptoms >2g/day
cyanocobalamin (B12)
- cobalt and corrin ring system
- fatty acid oxidation
- active form
methyl cobalamin
- active form
- methionine synthesis from homocyteine forming tetrahydrofolate
- isomerization of methyl malonyl CoA from odd chain FA oxidation
Reactions that use B12
1) Homocysteine via homocysteine methyltransferase to methionine
N5-methyltetrahydrofolate to tetrahydrofolate --> methylcobalamin
2) odd # FA methylmalonyl CoA methylmalonyl CoA mutase (deoxyadenosylcobalamin) --> succinyl coA
Steps in B12 metabolism
1) Vitamin B12 complexes with R factor in saliva

2) Intrinsic factor (IF) from parietal cells in body + fundus of stomach
- IF necessary for reabsorption in terminal ileum.

3) Pancreatic enzymes cleave off R factor, which allows vitamin B12 to complex with IF

4) Vitamin B12 – IF complex is reabsorbed in terminal ileum

5) After reabsorption, vitamin B12 is bound to transcobalamin in plasma + delivered to metabolically-active cells or stored in liver.
Pernicious Anemia
- no B12 = no intrinsic factor due to AI destruction of parietal cells
- tx: IM injections of cyanocobalamin
- anemia reversible, but not CNS effects
megaloblastic anemia
- ↓ in B12 or folic acid --> ↑ in plasma homocysteine levels --> damages blood vessels and poses risk for thrombosis
- tx: folate and B12
B12 deficiency
- No IF
- low folate and B12
- pure vegan diet
- chronic pancreatitis (can't cleave off R factor)
- terminal ileal disease (Chron's)
Source of Biotin
- bacterial synthesis in intestine
Function of Biotin
Cofactor in:
- carboxylation (pyruvate carboxylase and acetyl coA carboxylase, proionyl carboxylase)
Biotin deficiency
- raw egg whites (avidin)
- broad spectrum antibiotics
Folic Acid
- tetrahydrofolate deritives
- 1-C transfer reactions in DNA synthesis
Metabolism of Folic Acid
1) polyglutamates --> monoglutamates in jejunum by intestinal conjugase enzyme
2) Monoglutamate reabsorbed in jejunum
3) circulates as methyltetrahydrofolate
- 3-4 month supply in liver
drugs that inhibit folic acid
1) methotrexate and trimethoprim inhibit dihydrofolate reductase --> no purine and pyrimidine biosynthesis --> kills blast cells --> macrolytic anemia
2) phenytoin --> I of intestinal conjugase
3) OCP --> block reabsorption of monoglutamate in jejunum
4) EtOH --> block reabsorption in jejunum
5) rapidly growing cancers
6) small bowel malabsorption (celiac disease)
7) sulfa drug inhibits folic acid synthesis
- inhibits dihydrofolate reductase preventing AA, Purine and thymidine synthesis
- inhibits dihydropteroate synthetase (PABA + pteridine precursor into folic acid)
Ascorbic acid
- coenzyme in hydroxylation especially proline and lysine
- prevention of formation of free radicals
- vitamin c deficiency
- cigarette smoking
Vitamin A components
1) retinol
2) retinal
3) retinoic acid
precursor of Vitamin A
β- carotene

- 2 molecues of retinal liked at aldehyde ends
topical form of vitamin A
- retinoic acid (all trans)
metabolism of vitamin A
1) β carotene cleaved by β-carotene dioxygenase in intestine --> retinal
2) retinaldehyde reductase(+ NADPH)reduces retinal to retinol
3)retinol --> palmitic acid --> blood via chylomicron --> liver uptakes and stores as a lipid ester within lipocytes
5) hydrolyzed retinol binds to RBP complex transported to golgi and secreted, in extrahepatic tissues retinol binds to cellular retinol binding protein (CRBP) plasma transport via albumin as retinoic acid
β-carotene dioxygenase
- cleaves β carotene in intestinal lumen to yield 2 retinal
retinaldehyde reductase
- reduces retinal to retinol with NADPH
transport of retinol from liver to extrahepatic tissue
- binding of hydrolyzed retinol to aporetinol binding protein (RBP)
aporetnol binding protein (RBP)
- liver to extrahepatic tissue by binding to hydrolyzed retinol
cellular retinol binding protein (CRBP)
- retinol binds within extrahepatic tissues
- moves from cytosol to nucleus
How is retinoic acid transported in the plasma?
binding to albumin
Hormonal action of retinol and retinoic acid
- steriod/thyroid hormone superfamily
- earliest processes of embryogenesis --> differentiation of the 3 germ layers. organogenesis and limb development
Which vitamins act like steroid hormones?
- retinol and vitamin D
which form of vitamin A is involved in vision?
- 11- cis retinal coupled + opsin to form rhodopsin
- rhodopsin + transducin (G protein)↑ GTP binding
- cGMP --> Na+ channels open
- cGMP phosphodiesterase
- ↓ in cGMP closes channels --> hyperpolaization of rod cell
- with light: 11-cis --> all trans retinal --> activation of transducin -->
non visual roles of retinol
1) mucous production by phosphorylation of retinol to retinyl phosphate
2) appetite and bone growth
3) spermatogenesis
4) prevention of fetal resorption (retinal and retinol)
5) maintenance of epithelial cells and mucus secretion
retinyl phosphate
- P activates
- synthesizes glycoproteins and mucopolysaccharides
- similar to dolichol p
retinoic acid
- required for appetite and bone growt
- used to treat mild acne (Darier's disease)
- all- trans retinoic acid
- topical antiaging
- 13-cis retinoic acid
- severe acne (oral)
- teratogenic
- hyperlipidemia
dietary deficiency of vitamin A
- night blindness is 1st sign
- ↑ susceptibility to infection and cancer
- xeropthalmia
- keratinization of the cornea
- severe Vitamin A deficiency
Hypervitaminosis A
- > 7.5 mg/ day
- dry, pruritic skin
- hepatomegaly
- ↑ Intracranial pressure
- teratogenic
storage of vitamin A
- retinyl esters in liver and adipose
- steroid horomone
- 1,25- dihydroxy vitamin D3
- calcitrol
Functions of Vitamin D
- Ca regulation
- Phosporous homeostasis
- Vitamin D2
- Plant
- vitamin D3
- animal
- endogenous precursor
- --> colecalciferol in dermis and epidermis with sunlight
Activation of D2 and D3
1) 25 hydroxylase in liver
2) 25 cholecalciferol-1-hydroxylase in kidney
3) 1,25-dihydroxycholecalciferol (1,25-diOHD3)
Activation of 25 cholecalciferol-1 hydroxylase
- ↓ plasma phosphate or Ca (indirectly through PTH)
Inhibition of 25-cholecalciferol-1-hydroxylase
- feedback inhibition by 1,25 vitamin D3
Vitamin D in liver
25 hydroylase
Vitamin D in kidney
25 cholecalciferol-1-hydroxylase
Function of Vitamin D
- ↑ plasma Ca++
- stimulates Ca and Phosphate uptake by intestine by inducing synthesis of a Ca-binding protein
- ↑ Ca reabsorption by the kidney
- mobilizes bone Ca by reabsorption
- collagen matrix formed by mineralization incomplete
- bow-legged
- mutation in vitamin D receptor --> D- independent rickets
- demineralization of bones
- more severe in northern lattitudes (less sunlight)
Renal rickets
- chronic renal failure
- low synthesis of 1,25 vitamin D3 (calcitrol)
Toxicity of Vitamin D
- stored in liver and fat
- loss of appetite, nausea, thirst, stupor, hypercalcemia --> Ca deposits in arteries and kidneys
Vitamin K
- posttransational carboxylation of blodd clotting factors
forms of vitamin k
1) phylloquinone --> K1 (plants)
2) menaquinone --> K2 (intestinal bacteria)
3) menadione-->synthetic derivative of K1
Requirements of Vitamin K
- hepatic synthesis of:
1) prothrombin
2) clotting factors, II, VII, IX and X
- sythesized as inactive precursor molecules
what is the formation of mature clotting facotrs dependent on?
- vitamin k dependent carboxylation of glutamic acid residue
What inhibits the formation of GLA?
- dicumarol and warfarin
Where is GLA present?
- osteocalcin of bone and other unrelated proteins of clotting
What is GLA?
- γ-carboxyglutamyl residue
vitamin K dependent carboxylase
- glutamate to γ-carboxyglutamyl residue
interaction of prothrombin with platelets
- γ-carboxylates chelate Ca, prothrombin --> membrane phospholipids in platelets
- conversion to thrombin
- antibiotics can cause in very ill, undernourished patients
what have warfarin like activity?
- second generation cephalosporins
what population is deficient in vitamin K?
- newborns with breast milk below RDA
toxicity with vitamin K
- prolonged treatment --> hemolytic anemia, jaundice in infants (RBC membrane effects)
Vitamin E function
- antioxidant
- inhibits non-enzymatic oxidation by free radicals
- scavenges peroxy-free radicals
- conjugated to glucuronate and excreted in bile
deficiency of vitamin E
- premature infants
- defective lipid transport/absorption --> RBC membrane fragility and abnormal cell membranes