chapter 13: water soluble vitamins

  1. why do water-soluble vitamins have less risk of toxicity
    • because they dissolve in water
    • are readily excreted
  2. what is an apoenzyme
    inactive enzyme form
  3. what is a holoenzyme
    active enzyme, formed when apoenzyme and coenzyme come together
  4. enrichment vs fortification
    • enrichment - addition of nutrients that were lost during processing
    • fortification - addition of nutrients into processed foods whether they were part of the food or not
  5. what is B1
  6. 4 function of thiamin (B1)
    • thiamin pyrophosphate (TPP) is a coenzyme in the metabolism of carbohydrates, branched chain AAs, and pentoses
    • helps convert pyruvate to acetyl CoA for citric acid cycle
    • synthesis of neurotransmitter acetylcholine
    • helps with synthesis of RNA
  7. sources of thiamin
    • pork
    • sunflower seeds
    • legumes
  8. how is thiamin absorbed, transported, stored, excreted
    • A - in the jejunum by carrier mediated system
    • T - by RBC in the blood in its coenzyme form
    • S - small reserve in liver and muscles, poor storage
    • E - excess quickly excreted in urine
  9. 2 main deficiency diseases of thiamin
    • Beriberi - dry, wet, infantile. occurs where polished rice is the only staple, occurs within 7 days, neuro/cardiovasc problems
    • Wernicke-Korsakoff syndrome - aka cerebral beriberi, alcohol diminishes absorption and increases thiamin excretion
  10. what is B2
  11. structure of riboflavin
    three linked 6-membered rings with sugar alcohol attached to middle ring
  12. 3 functions of riboflavin
    • energy metabolism in citric acid cycle
    • helps activate other B vitamins to their active forms
    • antioxidant
  13. co-enzymes of riboflavin
    • flavin monoculeotide (FMN)
    • flavin adenine dinucleotide (FAD)
  14. sources of riboflavin
    • a quarter from milk products
    • enriched grains
    • eggs
    • meat
  15. what destroys riboflavin
    UV light and radiation, but it is stable in heat
  16. how is riboflavin digested, absorbed, transported, stored, and excreted
    • D - Hcl in stomach releases riboflavin from its bound form
    • A - active or facilitated transport during low to moderate intake, but passive absorption during high intake
    • T - by protein carrier in the blood
    • S - small amount stored in lover
    • E - excess secreted can cause urine to turn bright yellow
  17. main riboflavin deficiency disease
    • ariboflavinosis
    • alcoholics, users of phenobarbital, avoidance of milk products
    • symptoms - glossitis, stomatitis, seborrheic dermatitis, affects mouth, skin, RBCs
  18. what is B3 and its two forms
    • niacin
    • nicotinic acid (niacin)
    • nicotinamide (niacin amide)
  19. function of niacin/B3
    • synthesizes NAD+ and NADP+
    • coenzyme in oxidation-reduction reactions (glycolysis, CTA, fatty acid synthesis)
  20. food sources of niacin
    poultry, meat, fish, mushrooms
  21. what can niacin be synthesized from
    • tryptophan
    • found in protein rich foods
  22. 1 mg niacin = _____ mg tryptophan
    60 mg
  23. 1 gram of protein = _____ mg tryptophan
    10 mg
  24. what is NE (the unit)
    niacin equivalents
  25. how is niacin absorbed, transported, stored, and excreted
    • A - readily absorbed from stomach and SI, active and passive
    • T - from liver to all of the tissues where it is converted to coenzymes
    • E - excess excreted in urine
  26. niacin diseases, 3 D’s, susceptible populations
    • pellagra - diarrhea, dementia, dermatitis
    • can be prevented with adequate protein diet
    • those who consume corn as main staple are susceptible + alcoholics
  27. what is hartnup disease
    rare genetic disorder where tryptophan to niacin pathway is blocked
  28. toxicity effects of niacin
    • flushing of skin
    • itching
    • nausea
    • liver damage
    • UL = 35 mg
  29. functions of pantothenic acid
    • part of coenzyme A (for formation of acetyl coA for citric acid cycle)
    • forms acyl carrier protein involved in fatty acid elongation
  30. food sources of pantothenic acid
    • meat, milk, many veggies
    • freezing, canning, refining will destroy PA
    • unprocessed foods are better sources
  31. deficiency for pantothenic acid
  32. ATSE of pantothenic acid
    • A - absorbed as pantothenic acid from SI
    • S - minimal storage as coenzyme in liver
    • E - readily excreted in urine
  33. pantothenic acid deficiency diseases
    • rare
    • burning foot syndrome
    • fatigue
    • HA
    • alcoholics at risk
  34. function of biotin
    • cofactor in carboxylase reactions (adds CO2 to compounds)
    • formation of oxalacetate
    • fatty acid synthesis and breakdown
    • allows for breakdown of AA for use as energy
  35. ATSE for biotin
    • A - exists in free and protein bound forms (biocytin), which has to be cleaved from protein by biotinidase before being absorbed in SI
    • S - stored in small amounts in muscle, liver, and brain
    • E - excreted via urine and bile
  36. what can cause biotin deficiency
    • rare
    • high intake of raw eggs bc it has Avidin -> which inhibits absorption
    • alcoholism
    • anticonvulsant drug use
    • biotinidase deficiency
  37. what are the 3 forms of Vitamin B6 and how are they activated
    • pyridoxal
    • pyridoxine
    • pyridoxamine
    • the 3 forms can be phosphorylated to become active vitamin B6 coenzyme
  38. main coenzyme form of B6
    pyridoxal phosphate (PLP)
  39. function of Vitamin B6
    • decarboxylation of AA
    • transamination reaction
    • rearrangement of AA
    • conversion of tryptophan to niacin
    • helps regular blood glucose level
    • needed to make red blood cells and hemoglobin
  40. food sources of B6
    • meat
    • fish
    • poultry
    • carrots, potato, oatmeal
    • spinach
    • more readily absorbed from animal foods
    • lost during resining of grains
  41. ATSE of vitamin B6
    • A - passively, all 3 forms phosphorylated in liver
    • T - binds to albumin for transport in blood
    • S - stored in liver and muscle tissue
    • E - through urine
  42. B6 deficiencies
    • rare
    • microcytic hypochromic anemia - small, pale RBCs that have decreased oxygen carrying abilities
    • reduced immune function
    • peripheral nerve damage
    • susceptible to alcoholics, ppl with genetic defect for anemia, medication interactions
  43. function of folate
    • influences DNA methylation
    • DNA synthesis
    • AA metabolism
    • neurotransmitter synthesis
  44. sources of folate
    • liver
    • legumes
    • leafy greens
    • susceptible to heat, oxidation, UV light
  45. what is DFE and how is it calculate
    • dietary folate equivalents
    • DFE = (total synthetic folate x 1.7) + total food folate intake
  46. ASE for folate
    • A - to be absorbed has to be broken down into mono glutamate in GI tract with the help of folate conjugase
    • S - mainly liver, once transported into cell it is converted into polyglutamate form so it is trapped in cell
    • E- in ruine and bile
  47. 2 main folate deficiencies
    • megaloblastic anemia - larger than normal RBCs, unable to divide or make it out of bone marrow, aka macrocytic anemia
    • neural tube defects -> spina bifida or anencephaly
    • susceptible ppl = alcoholics and pregnant women bc increased rate of cell division and DNA synthesis in mother and baby
  48. 3 forms of vitamin B12
    • cyanocobalamin (free vitamin B12)
    • methylcobalamin (coenzyme form)
    • 5-deoxyadenosylcobalamin (coenzyme)
  49. only vitamin that contains cobalt
  50. functions of vitamin B12
    • formation of methionine and homocysteine AAs
    • coenzymes move 1-carbon groups in CTA, oxidation of FAs, folate metabolism
  51. sources of B12
    • animal products
    • vulnerable to heat
  52. ATSE for B12
    • A - free vitamin B12 binds to R-protein from salivary gland, released by HCL and pepsin in stomach, binds to IF, this complex binds to boarder cell receptors for absorption
    • about 50% absorbed
    • T - transcobalamin II binds to absorbed vitamin B12, transports it through portal vein, taken up by liver, bone marrow, RBCs
    • S - 50-90% of body’s supply is stored in liver
    • E - very little through bile, reabsorbed by enterohepatic circulation
  53. what can disrupt vitamin B12 absorption
    • absence or defective synthesis of R-protein, IF, or pancreatic proteases
    • defective binding to IF
    • removal of ileum or stomach
  54. 2 vitamin B12 deficiency diseases + treatment
    • pernicious anemia - decrease in RBS when body cant properly absorb B12 bc of lack of production of IF
    • macrocyctic anemia - too much homocysteine can damage endothelial cells
    • treatment = monthly injections, nasal gel, oral doses
  55. why is choline not a B vitamin
    bc it does not have coenzyme function
  56. function of choline
    • precursor for compounds that enable cell membranes to form
    • involved in export of VLDL from liver -> prevents it from accumulating in liver
    • assists in conversion of homocysteine to methionine -> another way to decrease homocysteine levels
  57. what is lecithin
    component of cell membranes that helps make myelin for nervous system
  58. food sources of choline
    • in form of lecithin
    • milk
    • liver
    • eggs
    • peanuts
    • animal sources are largest sources
  59. deficiency of choline
  60. ASE for choline
    • absorbed from SI via transport protein
    • all tissues store and contain choline
    • some excreted in urine
  61. two forms of vitamin C
    • ascorbic acid (reduced)
    • dehydroascorbic acid (oxidized)
  62. functions of vitamin C
    • antioxidant
    • collagen synthesis
    • enhances non heme iron absorption
  63. sources of vitamin C
    • fruit
    • veggies
    • fortified cereals
  64. ASE of vitamin C
    • A - by specific energy dependent transport system in SI, passive if intake is high, decreased absorption if intake is high
    • S - high content stored in pituitary and adrenal glands, WBC, brain, eyes
    • E - via kidneys
  65. vitamin C deficiency disorder
  66. what inhibits vitamin C absorption
    pectin and zinc
Card Set
chapter 13: water soluble vitamins
ch 13