Nutrition II Flashcards
What are the symptoms of vitamin B6 deficiency?
Convulsions, hyperirritability, peripheral neuropathy, sieroblastic anemias due to impaired hemoglobin synthesis and iron excess (p.91)
What can cause a B6 deficiency?
Izoniazid; oral contraceptives (p.91)
What is the function of Vitamin B7 (biotin)?
Serves as a cofactor for carboxylation enxymes which add 1 carbon group: pyruvate carboxylase (pyruvate –> oxaloacetate); Acetyl-Co-A Carboxylase (acetyl-CoA –> malonyl-CoA); Propionyl-CoA carboxylase (propionyl CoA –> methylmalonyl-CoA) (p.92)
What are the causes of vitamin B7 deficiency?
Quite rare; caused by antibiotic use or excessive ingestion of raw eggs (avidin) (p.92)
What are the symptoms of vitamin B7 deficiency?
Dermatitis, alopecia, enteritis (p.92)
What is the function of Vitamin B9 (folic acid)?
Converts to tetrahydrofolate (THF), a coenzyme for 1-carbon transfer/methylation reactions and is important for the synthesis of nitrogenous bases in DNA and RNA (p.92)
What foods are rich in Vitamin B9?
Leafy green vegetables (p.92)
Is Vitamin B9 stored?
Small reserve pool primarily in the liver (p.92)
What are the symptoms of Vitamin B9 deficiency?
Macrocytic, megaloblastic anemia; no neurologic symptoms (as opposed to vitamin B12 deficiency) (p.92)
What can cause a Vitamin B9 deficiency?
Alcoholism, pregnancy, drugs (phenytoin, sulfonamides, MTX) (p.92)
What is the function of Vitamin B12 (cobalamin)?
Cofactor for homocysteine methyltransferase (transfers CH3 groups as methylcobalamin) and methylmalonyl-CoA mutase (p.93)
Where is cobalmin synthesized?
Only by microorganisms (p.93)
What are the three most common causes of Vitamin B12 deficiency?
Malabsorption (sprue, enteritis, Diphyllobothrium lactum), lack of intrinsic factor (pernicious anemia, gastric bypass), or absence of terminal ileum (Crohn’s disease) (p.93)
What test is used to detect the etiology of a B12 deficiency?
Schilling test (p.93)
What is the clinical presentation of B12 deficiency?
Macrocytic, megaloblastic anemia, hypersegmented PMNs, neurologic symptoms (paresthesias, subacute combined degeneration) due to abnormal myelin. Prolonged deficiency leads to irreversible damage (p.93)
What is the composition of S-adenosyl-methionine?
ATP + methionine –> SAM (p.93)
What is the function of SAM?
SAM transfers methyl units and is required for the conversion of NE to epinephrine
What cofactors are necessary for the regeneration of methionine and SAM?
Vitamin B12 and Folate (p.93)
What is the function of Vitamin C?
An antioxidant that also facilitates iron absorption by keeping iron in its Fe2+ reduced state. Necessary for the hydroxylation of proline and lysine in collagen synthesis (scurvy –> collagen synthesis defect) and necessary for dopamine B hydroxylase which converts dopamine to NE (p.94)
What are the symptoms of Vitamin C overdose?
Nausea, vomiting, diarrhea, fatigue, sleep problems, increased risk of iron toxicity (for pts with transfusions or hereditary hemochromatosis) (p.94)
What are the four forms of Vitamin D?
D2= ergocalciferol; D3= cholecalciferol; 25-OH D3, 1,25- (OH)2D3= calcitrol (p.94)
How are adequate sources of Vitamins D2 and D3 attained?
D2- ingested from plants; D3- consumed in milk and formed in sun exposed skin (p.94)
What is the difference between 25-OH D3 and 1,25-(OH)2D3?
25-OH D3 is the storage form; 1,25- (OH)2D3 is the active form (p.94)
What is the function of Vitamin D?
Increases intestinal absorption of calcium and phosphate, increases bone mineralization (p.94)
What are four consequences of Vitamin D deficiency?
Rickets in children; osteomalacia in adults; hypocalcemic tetany; decreased Vitamin D in breast milk (p.94)
