Water Soluble Vitamins Flashcards

1
Q

Thiamine characteristics?

A

Active form: thiamine pyrophosphate (TPP)

TPP is involved in alpha-keto acids

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2
Q

What are the two types of thiamine transporter?

A

THTR 2 (low or normal concentrations, active transport)

THTR 1 (high concentration, passive)

Alcohol affects only the THTR 2 carrier mediated transport

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3
Q

Thiamine deficiency leads to…

A

Wet beri-beri (edema and CV problems)

Dry beri-beri (neurological problems)

Wernicke-Korsakoff syndrome: CNS lesions, associated with alcoholism

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4
Q

Riboflavin (Vitamin B2)

A

Is readily destroyed by sunlight

Active forms are FMN (can be reduced to FMNH2) and FAD (can be reduced to FADH2)

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5
Q

Riboflavin deficiency

A

Stomatitis (inflammation of mouth)

Cheilosis (painful cracking of corners of mouth)

Glossitis (inflammation of tongue)

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6
Q

Niacin

A

Active forms: NAD+, NADP+; serve as coenzymes in RedOx reactions

Tryptophan can make NAD, de novo

ADP ribose can help convert NAD to nicotinamide

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7
Q

How does niacin help lower LDL and increase HDL?

A

Decrease in LDL is due to noncompetitive inhibition by niacin on a liver enzyme involved in triglyceride synthesis

This decreased synthesis results in intracellular apo B degradation and decreased secretion of VLDL particles

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8
Q

Niacin deficiency characteristics

A

Pellagra: dermatitis, dementia, diarrhea (3 D’s); also caused by insufficient tryptophan

Hartnup’s dx: affects amino acid transport; an increased need for niacin may lead to its deficiency

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9
Q

Biotin

A

The enzyme biotinidase removes bound biotin from protein (a good thing!)

Deficiency of biotinidase results in increased fatty acid production; also, body becomes biotin deficient

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10
Q

Biotin deficiency

A

Caused by defects in reutilization (not diet); see biotinidase

Absence of holocarboxylase synthase enzyme causes multiple carboxylase deficiency

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11
Q

Panthothenic acid

A

Is a component of coenzyme A (CoA)

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12
Q

Folic acid

A

Consists of pteridine attached to PABA and a glutamic acid

Monoglutaminated folic acid is taken up by the reduced folate carrier (RFC) in the intestine

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13
Q

Formation of tetrahydrofolic acid (THF) is inhibited by…

A

Methotrexate, a treatment option which inhibits the dihydrofolate reductase

Also, anything affecting vit B12 production will also affect folate production

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14
Q

Megaloblastic anemia

A

Is caused by diminished synthesis of purines and thymidine, leading to the inability of cells to both divide and make DNA

Macrocytic RBCs are seen (no cell division, so the cells keep growing)

Transulfuration pathway needs vit B6

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15
Q

Spina Bifida

A

Is caused by a C -> T substitution (valine for alanine)

May account for neural tube defect

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16
Q

Histidine load test is used for?

A

Measuring FIGLU and seeing if there is a deficiency in folic acid

If FIGLU is high in the urine sample, THF is therefore low, because it would have converted the FIGLU into other things (if things were normal, FIGLU would not be high in the urine)

17
Q

Dietary Vitamin B12 overview

A

B12 binds to transcobalamin I in the stomach which then travel to the intestine and are then destroyed by pancreatic proteases

The freed B12 then binds to intrinsic factor (IF), and then are absorbed by ileum and then carried by transcobalamins

18
Q

Absorption and transport of Vit B12

A

B12 is bound by transcobalamin II when transported to the tissues

19
Q

Dx and deficiencies associated with B12

A

Crohn’s Dx: affects ileum so that there is an impairment of bile acid and B12 absorption

Dx sx: megaloblasic anemia, pernicious anemia (if lacking IF), homocystinuria (homocysteine does not convert to methionine) and methylmalonic aciduria

20
Q

Methylmalonic aciduria characteristics

A

Propionyl CoA —biotin—> methylmalonyl CoA –vit B12–> succinyl CoA -> citric acid cycle and gluconeogenesis

If vit B12 is deficient, MM CoA cannot convert to succinyl CoA; thus, MM CoA builds up (bad!)

21
Q

Pyridoxine (Vit B6)

A

Pyridoxal phosphate (PLP) is the active form

PLP is essential for transaminase rxns and the synthesis of the NTs (serotonin, epi, norepi and GABA)

PLP also required for synthesis of alanine (precursor of heme)

22
Q

Vitamin B6 deficiency

A

Causes hypoglycemia due to impairments of glycogenolysis and gluconeogenesis

May cause sideroblastic microcytic anemia

23
Q

How to test for vit B6 defiency

A

Tryptophan load test

Trp usually ends up forming alanine, because PLP cleaves kynurenine. If PLP is deficienct, it, instead, leads to an increase in xanthurenic acid, a measurable quantity after a load test.

24
Q

Ascorbic acid / Vitamin C

A

Important for collagen formation

Deficiencies lead to weak collagen, bleeding gums, poor wound healing and petechiae