NS 3310: Final Exam
41 Cards in this Set
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What is the pathway of Vitamin A absorption?
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Retinol combines with fat into a micelle, which is absorbed in the enterocyte. Retinol is converted into retinyl ester and then packaged into CM-->Lymph.
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11-cis retinal
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Vitamin A
Vision, contained with rhodopsin. When retinal is released, leaves opsin.
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Vitamin A deficiency
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Nyctalopia: night blindness
Dry eye
Keratinization of cells
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Vitamin A toxicity
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Anorexia
Dermatitis
Headache
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What is the pathway of Vitamin D absorption?
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Synthesized in the dermis by UV light. Cholesterol to 7-dehydroxycholesterol to D3 by UV light. D3 binds to DBP and is transported in blood. Liver hydroxylates into 25-OH-D3 (measurable). Kidney deactivates with 24-hydroxylase into 24,25(OH)2-D3
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What is 1alpha,24(OH)2-D3?
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Product of Vitamin D absorption. Increases calcium absorption.
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Vitamin D Toxicity
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Cannot be toxic via sunlight (lumisterol is the overflow pathway)
PABA lowers in blood
Too much serum Calcium
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Vitamin D Deficiency
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Rickets
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How does phosphorus affect Vitamin D?
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increases the production of 24,25(OH)2-D3
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What is L-gulonolactone oxidase?
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enzyme used to synthesize Vitamin C. Humans do not have this enzyme.
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How is Vitamin C absorbed?
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Tissues absorb from plasma.
Mononuclear leukocytes have higher concentration. (Na-dependent L-ascorbic acid transporter)
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What does Vitamin C do?
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Aids in the hydroxylation of prolyl and lysyl groups in procollagen. Antioxidant that donates electrons to oxidized substances.
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What is the Renal Threshold?
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0.8mg/100mL of Vitamin C in the body at a time or more will be excreted in the urine.
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How is Folate absorbed?
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Brush border conjugates release all but 1 glutamate to make THF. THF is transported in intestinal mucosa via receptor-mediated processes. In the mucosa, THF gains a methyl group into 5-methyl-THF and is transported in the blood. Tissues take this form
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What is polyglutamation and what vitamin does it pertain to?
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Polyglutamation is adding glutamates to the tail of Folic Acid (Folate). Causes folate to be "locked" in the cell. Demethylation must occur first, but requires Vitamin B12.
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What is the function of Folate?
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5,10-methylene THF is required for DNA synthesis and hematopoiesis. Aids in transforming homocysteine to methionine with B12.
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What are the causes and outcomes of a Folate deficiency?
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B12 deficiency can cause a folate deficiency as well as a folate deficiency.
Can cause megaloblastic anemia, which is different from microcytic anemia.
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How do you measure the status of folate?
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Measure 5-methylTHF
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What is FIGLU?
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Derived from histidine and plays a role in folate absorption. THF is required to convert FIGLE to glutamate. This can also be caused by a Vitamin B12 deficiency.
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How is Vitamin B12 absorbed?
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In the stomach, intrinsic factor, HC and HCl are released by parietal cells in stomach. HCl dissociates B12. B12 forms a complex with intrinsic factor and enters enterocytes. Once in the enterocyte B12-IF dissociates. B12 transported to blood via TC11
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What is adenosylcobalmin?
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A cofactor for methymalonyl-CoA mutase that converts methylmalonyl CoA to succinyl CoA
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What is Methylcobalamin?
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A cofactor for methionine synthetase to convert homocysteine to methionine (methyl carrier from 5-methyl-THF.
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Which of the vitamins is hematopoietic?
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Vitamin B12 and folate. And Vitamin B6.
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How can a Vitamin B12 deficiency occur and what are the consequences?
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Only found in animal products.
Can cause folate deficiency and megaloblastic anemia.
Methylmalonyl CoA accumulates and will spontaneously form methylmalonic acid that is secreted in the urine.
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What is methylmalonic acid?
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A build up of methylmalonyl CoA due to a Vitamin B12 deficiency. Can be measured for Vitamin B12 status.
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How is Vitamin B6 absorbed?
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PN is eaten in the diet. PLP is eaten from the diet, phosphorylated prior to consumption.
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How is Vitamin B6 activated?
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PN and PL are phosphorylated to become biologically active. The constant degradation/oxidation produces pyridoxic acid that is excreted in the urine.
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What is pyridoxic acid?
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Produced by oxidation of PN and PL. Excreted by urine. Vitamin B6.
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What is the function of Vitamin B6?
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Coenzyme for glutamate-Oaa aminotransferase which converts aspartate to OAA (forms glutamate).
PLP is a coenzyme for aminolevulinic acid synthase to produce heme.
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What is the result of a B6 deficiency?
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B6 deficiency = no heme = no hemoglobin = no RBC. Leads to microcytic anemia.
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What is Xanthurenate?
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Excreted during a vitamin B6 deficiency. Formed from tryptophan/methionine reaction.
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What is another name for Vitamin B1?
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Thiamin
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How is thiamin absorbed?
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Needs to be phosphorylated into thamin pyrophospate to be activated.
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What is the function of thiamin?
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Is a coenzyme for pyruvate dehydrogenase and transketolase in the PPP.
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What is a deficiency in thiamin called?
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Beri Beri (I can't, I can't) Multiple inflammatory changes in nerves. Muscle debility.
Polyneuritis: muscle paralysis.
Opthalmoplegia: infants. Muscle paralysis in eyes.
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How do you measure thiamin status?
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Blood levels of pyruvate.
Urinary levels of thiamin.
RBC transketolase activity.
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What is the function of Vitamin B3 (Niacin)?
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NAD--functions in energy metabolism through redox reactions. Carries electrons for ETC.
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Nicotinic Acid
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Increases HDL by decreasing cAMP in adipose. Which decreases HSL. It also has an antihyperlipidemic effect.
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What is a deficiency in Niacin?
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Diarrhea
Dementia
Dermatitis
Death.
Pellagra.
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How do you measure Niacin status?
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N-methyl nicotinamide in urine.
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What is N-methyl nicotinamide?
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Product of Niacin metabolism.
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NS 3310: Final Exam