Water soluble vitamins Flashcards
where are water soluble vitamins absorbed?
portal blood
do water soluble vitamins circulate in free or bound form?
free
are water soluble vitamins stored?
no
what are the fat soluble vitamins?
A, D, E, K
how are fat soluble vitamins absorbed?
via bile salts
do fat soluble vitamins circulate in free or bound form?
bound to carrier protein
are fat soluble vitamins stored?
to some extent by body fat
definition: dietary reference intake (DRI)
- set of reference values used to plan and assess nutrient intakes of healthy people and varies by gender / life stage
- includes RDA, AI, EAR, TUL
definition: recommended dietary allowance (RDA)
average daily level of intake sufficient to meet the nutrition requirements of nearly all healthy people
definition: adequate intake (AI)
established when evidence is insufficient to develop an RDA and is set at a level assumed to ensure nutritional adequacy
definition: estimated average requirement (EAR)
expected to satisfy the needs of 50% of the people in that age group based on a review of the scientific literature
what is the role of vitamin B1 (thiamine)?
oxidative decarboxylation of a-keto acids and 2-keto sugars
what is the role of vitamin B2 (riboflavin)?
electron (hydrogen) transfer reactions
what is the role of vitamin B3 (niacin)?
electron (hydrogen) transfer reactions
what is the role of vitamin B6 (pyridoxine)?
coenzyme in many transamination and decarboxylation reactions
what is the role of biotin?
CO2 transfer reactions, carboxylation reactions
what is the role of folate?
one carbon methyl transfers, amino acid metabolism
what is the role of vitamin B12 (cobalamin)?
- methylation of homocysteine to methionine
2. conversion of methylmalonyl CoA to succinyl CoA
what is the role of vitamin C?
- antioxidant
- collagen synthesis
- immune function
- absorption of non-heme iron
what are the energy releasing B complex vitamins?
- B1 (thiamine)
- B2 (riboflavin)
- B3 (niacin)
- pantothenic acid
- biotin
- B6
what are the hematopoietic B complex vitamins?
- folate
- B12
- pantothenic acid
- B6
how does vitamin C affect iron metabolism?
increases absorption of non-heme iron in gut and helps with distribution of iron in body
which B vitamins are involved in the metabolism of fat and carbohydrates?
thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid, biotin
which B vitamin is involved in the metabolism of protein?
B6
what is the role of B12 in homocysteine metabolism? what form must B12 be in?
- catalyzes remethylation of homocysteine to methionine requiring 5-methyl-THF
- methyl cobalamin
what is the role of B6 and pantothenic acid in hemoglobin metabolism?
synthesis of heme
what condition is associated with cobalamin deficiency?
pernicious anemia
what conditions are associated with folate deficiency?
megaloblastic anemia, neural tube defects
what enzyme acts as a methyl donor to convert homocysteine to methionine?
MTHF (methyltetrahydrofolate)
what is the cause of pernicious anemia?
- parietal cells fail to secrete intrinsic factor - B12 deficiency
- diphyllobothrium latum tapeworm
what is the methyl trap?
methyl trapped in the form of MTHF after being used as a methyl acceptor instead of a methyl donor for DNA synthesis
what is the cause of megaloblastic anemia?
folate deficiency - disruption of hematopoietic precursor maturation
folate deficiency during the first trimester of pregnancy can result in what condition?
neural tube defects - spina bifida
what is the risk of heavy folate supplementation?
can mask B12 deficiencies (cognitive impairment), particularly in elderly patients
what are the four Hs of scurvy?
- hemorrhage
- hyperkeratosis
- hypochondriasis
- hematologic abnormalities
pellagra is the result of deficiency of what vitamin?
Niacin (B3)
