B Vitamins Flashcards

6653030935	Vitamin B12	Found exclusively in foods of animal origin due to microbial synthesis or prior ingestion of the vitamin	0
6653138930	Vitamin B12 structure	corrin ring with cobalt incorporated into the center	1
6653147551	Three coenzyme forms of vitamin B12	Methyl, hydroxyl, and deoxyadenosyl-cobalmin	2
6653155483	Cyanocobalamin	form of vitamin B12 used in supplements and fortified foods	3
6653161010	Methyl and deoxyadenosyl-cobalamin	the two biologically active forms of vitamin B12; all forms are readily converted into these biologically active forms	4
6653179516	Impaired Vitamin B12 bioavailability	an excess intake of vitamin C > 500 mg/day	5
6653187701	Haptocorrin	a glycoprotein that binds free b12 and is secreted by salivary glands and swallowed with food; also called R-protein and transcobalmin I (TC-1)	6
6653205153	B12 gastric digestion	released from protein ingested via the action of HCl and pepsin in the gastric secretions	7
6653219278	B12 complex intestinal digestion	Transcobalamin I (TC1) complex travels into the small intestine where pancreatic proteases hydrolyze haptocorrin or R protein and free B12 is released	8
6653233385	Intrinsic factor	A glycoprotein produced by gastric parietal cells and forms complex with B12 in the duodenum; moves to ileum	9
6653252802	Cubulin	intrinsic factor receptor in the ileum where IF-B12 complex is absorbed; on GI epithelial cells	10
6653261519	TC-II	Vitamin B12 transporter protein after intestinal absorption; enters portal circulation, taken up first by liver, then bone marrow and erythrocytes	11
6653273149	Vitamin B12 storage	unlike other water-soluble vitamin, b12 can be stored in the liver	12
6653283929	B12 secretion	Vitamin B12 is secreted into the bile so most is reabsorbed via enterohepatic circulation	13
6653295436	Those at risk for B12 deficiency	Pancreatic insufficiency interferes with release of free b12, impaired HCl production, elderly, H2 antagonists or PPIs, removal of a portion of stomach, ileal resection, chronic malabsorption syndromes	14
6653310211	Methylcobalamin	cofactor for methionine synthetase which converts homocysteine to methionine	15
6653315550	Methyl trap	when b12 is lacking, 5-methyl-THF becomes trapped in its inactive form	16
6653325201	Deoxyadenosyl-cobalamin	form of vitamin B12 required for the conversion of methylmalonyl coenzyme A to succinyl coenzyme A Also required for the degradation of certain amino acids and odd chain fatty acids	17
6653344066	RDA for B12 ages 14 and up	2.4 micrograms	18
6653348518	Food sources of Vitamin B12	Fortified cereals, meat, fish, poultry, eggs	19
6653373566	Signs of B12 deficiency	cognitive decline, cardiovascular disease, bone fractures, megaloblastic anemia with macrocytosis, neutrophil hypersegmentation, bone marrow changes, leukopenia, thrombocytopenia; glossitis, constipation, diarrhea; hand and feet paresthesia, decline of vibration and/or position sense, unsteadiness, confusion, depression, mental slowness, poor memory; delusions and overt psychosis	20
6653395783	B12 toxicity	no toxicity known	21
6653398934	Normal B12	24.4-100 ng/dL serum B12	22
6653411528	B12 deficiency: in general	hematologic, GI, and neurological manifestations	23
6653413109	B12 deficiency in aging	cognitive decline, cardiovascular disease, and bone fractures	24
6653417964	B12 deficiency in malabsorption	Gastrectomy, gastric bypass, ileal resection, Crohn's disease; also in vegetarian populations; reduced HCl production; overgrowth of H.pylori	25
6653429635	Stage I Vitamin B12 deficiency	low serum vitamin B12	26
6653435524	Stage II Vitamin B12 deficiency	Low cell stores of vitamin B12	27
6653436952	Stage III vitamin B12 deficiency	A biochemical deficiency	28
6653439300	Stage IV vitamin B12 deficiency	A clinically apparent deficiency	29
6653445145	Serum holotranscobalamin II	earliest indicator of a compromise in b12 status	30
6653452863	When B12 levels are normal in deficiency	serum vitamin b12 can remain normal at the expense of cellular stores	31
6653459214	Serum methylmalonic acid (MMA) and serum homocysteine	these levels are elevated in greater than 90% of individuals with B12 deficiency	32
6653464387	Serum B12	procedure of choice for determining b12 status	33
6653471091	Treatment for B12 deficiency	100 or 1000-mcg IM injections at 1 month intervals until corrected; more frequently in symptomatic B12 deficiency	34
6653505202	Vitamin B12 recommendation for vegetarians	standard MVI	35
6653506282	Normal serum MMA	0.08 to 0.56 micromol/L	36
6653508804	Normal homecysteine level	5-15 micromol/L	37
6664713913	Thiamine	consists of a central carbon to which a nitrogen-containing ring and sulfur-containing ring are attatched	38
6664732996	Biologically active coenzyme of thiamin	Thiamin pyrophosphate (TPP) also known as thiamin diphosphate	39
6664750196	Thiamine digestion	before absorption, intestinal phosphatases hydrolyze the phosphates, leaving the free version	40
6664767302	Thiamine absorption	Mainly absorbed in the proximal small intestine, especially the jejunum, via a carrier mediated process. Absorption is passive with high intakes	41
6664796813	Most common cause of impaired thiamine absorption	Alcohol abuse	42
6664802074	Blood thiamine	Bound to albumin in the blood; majority of thiamine present in red bloods cells existing as TDP	43
6664825119	Key biological functions of thiamine	Energy transformation, synthesis of pentoses and NADPH, and membrane and nerve conduction	44
6664847563	Magnesium-coordinated activity of thiamine	TDP is a conenzyme for the oxidative decarboxylation of alpha-keto acids (pyruvate and alpha-ketoglutarate) which are involved in carbohydrate metaboism	45
6664881722	Transketolase	thiamine is a cofactor for this enzyme in the pentose phosphate pathway	46
6664897154	Thiamine: major causes of deficiency	Patients with recurrent vomiting, gastric surgery, alcoholism, or those with increased demand with marginal nutritional status; refeeding syndrome, dialysis, hyperemesis gravidarum, long-term PN	47
6664921934	Time for thiamine deficiency to occur	A deficiency can occur within 14 days without adequate intake or increased demand	48
6664934154	Standard prophylactic dose of thiamin	5-20 mg/d parenteral thiamine. Wider ranges between 50-300 mg/d (IV, IM, or oral) have been advocated	49
6664967509	Wernicke's encephalopathy: triad of symptoms	ocular abnormalities, gait ataxia, mental status changes	50
6664984041	Deficiency develops rapidly	Thiamine is usually first nutritional deficiency noted when food intake is limited or when absorption is impaired with alcohol abuse because deficiency develops rapidly	51
6664998385	Body stores of thiamine	30 mg	52
6665009286	Untreated thiamine deficiency	Results in fatal lactic acidosis	53
6665016667	Bariatric Beriberi	acute postgastric reduction surgery neuropathy; occurs alongside b12 deficiency	54
6665026182	Thiamine lab assay	Erythrocyte transketolase activity with and without the in vivo addition of TDP	55
6665032076	Normal transketolase	0-15%: acceptable thiamine status	56
6665039569	Low transketolase	stimulation of 16-24 % marginally deficient	57
6665047526	Deficient transketolase	stimulation greater > 25 % indicates high risk of deficiency	58
6665052617	Thiamine whole blood	values < 1.7 mcg/dL denote deficiency	59
6781167839	Cheilosis	Riboflavin, B6, Iron, ? zinc	60
6781172144	seborrheic dermatitis	Riboflavin (face and scrotum); B6	61
6781178127	Glossitis	Riboflavin, B6, iron	62
6783248044	Form of B6 in animal products	Pyridoxal (PL) and pyridoxial phosphate (PLP)	63
6783250671	Form of B6 in plants (more stable form)	Pyridoxine	64
6783256926	What extrahepatic tissue contains the most PLP?	Muscle, 75-80%	65
6783259330	What is the excreted form of vitamin B6?	4-pyridoxic acid	66
6783262278	Plasma B6	60% of B6 is present as PLP bound to albumin for transport AND hemoglobin in the enterocyte	67
6783266891	b6 enzymatic reactions	protein, amino acid, and lipid metabolism; gluconeogenesis; steroid receptor binding; central nervous center development; neurotransmitter synthesis, heme biosynthesis; normal immune function	68
6783279033	B6 deficiency post intestinal transplant	neuropmyopathic disorder associated with progressive muscle weakness and gait disturbances; PLP deficiency	69
6783283506	Lhermite sign	related to low B6 intake; affects the spinal cord	70
6783287302	B6 intake associated with negative effects	prolonged intake > 300 mg/day	71
6783289739	UL for B6 19 years and older	100 mg/day	72
6783294142	RDA B6 14-50 years of age	1.3 mg/day	73
6783295321	RDA > 50 years of age b6	1.7 men; 1.5 females mg/d	74
6783340294	Function of Biotin	Functions as cofactor for four carboxylase enzymes in mammalian systems (transports carbon dioxide to various substrates)	75
6783351386	Biotin is a cofactor for which carboxylases	acetyl-coenzyme A carboxylase, pyruvate carboxylase, propionyl-CoA carboxylase and 3 methlycrotonyl-ClA carbyoxylase	76