Biochemistry- Vitamins Flashcards by geet baghel

List the fat soluble vitamins

ADEK

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List the Water Soluble vitamins

B1, B2, B3, B5, B6, B7, B9, B12, C

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What are two primary sources of vitamin A ?

Liver and leafy vegetables

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What is the function of Vitamin A?

Antioxidant, essential for normal differentiation of epithelial cells into specialized tissue, retinal pigment

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What does Vitamin A prevent?

Squamous metaplasia

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What conditions is Vitamin A used to treat

oral for cystic acne
All-trans retinoic acid for AML subtype M3
Measles

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What issues does deficiency in vitamin A cause?

Night blindness, scaly and dry skin, corneal degeneration, bitot spots on conjunctiva, immunosuppression

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Acute toxicity of excess Vitamin A

Nausea, vomiting, vertigo and blurry vision

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Chronic toxicity of excess vitamin A

Alopecia, scaly skin, hepatomegaly, arthralgia, pseudotumor cerebri

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Why must a patient take two types of birth control and have a negative pregnancy test before taking vitamin A?

it’s a teratogen (cleft palate, cardiac abnormalities)

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What is ergocalciferol

Vitamin D2, derived from plants

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What is cholecalciferol

Vitamin D3, derived from milk and sun-exposed skin (stratum basale)

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What is the active form of Vitamin D?

1,25 (OH) D3 aka calcitriol. Synthesized by 1 alpha hydroxylase in the liver

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What does a deficiency in 1 alpha hydroxylase result in?

Rickets type 1 (AR)

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What is the function of vitamin D?

Increase absorption of calcium and phosphate in the intestines, increase bone mineralization at low levels and increase bone resorption at high levels

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What does a deficiency of Vit D lead to?

Rickets in children, osteomalacia in adults. Breastfed babies need supplemental Vitamin D

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What does an excess of Vitamin D lead to?

Hypercalcemia, hypercalciura, loss of appetite, stupor

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How does granulomatous disease lead to excess vitamin D?

Increased activation by macrophages

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What is the function of Vitamin E (tocopherol, tocotrienol)?

Antioxidant that protects RBCs and membranes from oxidative damage

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What are consequences of Vitamin E deficiency?

Hemolytic anemia, acanthocytes on histology, posterior column and spinocerebellar tract demyelination

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How is Vitamin E deficiency different from Vitamin B12 deficiency?

no megaloblastic anemia, no hypersegmented neutrophils, no elevation in serum methylmalonic acid

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Which vitamin enhances the anticoagulation effect of warfarinV

Vitamin E

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What is the function of Vitamin K

“K”oagulation; cofactor for gamma carboxylation of Glutamate residue of clotting proteins 2, 7, 9, 10 C and S.

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What two scenarios have Vitamin K deficiency?

Neonates (sterile intestines)

Prolonged use of broad-spectrum antibiotics (killing intestinal flora)

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What is the name if Vitamin B1

Thiamine

What is the function of Thiamine

TPP cofactor for most dehydrogenase enzymes in ATP-generating (glucose utilization) reactions

for which enzymes is Thiamine a cofactor

alpha-ketoglutarate dehydrogenase Transketolase Pyruvate dehydrogenase Branched-chain ketoacid dehydrogenase

How is B1 deficiency diagnosed?

Increased RBC transketolase activity after B1 infusion

What vitamin is Wernicke-Korsakoff a deficiency in?

Thiamine B1

What is the classic triad presentation of Wernicke-Korsakoff

Confusion, ophthalmoplegia, ataxia (+ personality change, permanent memory loss, confabulation)

What is damaged in Wernicke-Korsakoff?

Medial dorsal nucleus of thalamus, mammilary bodies

What is wet beriberi?

Dilated cardiomyopathy and edema due to B1 deficiency

What is dry beriberi?

Polyneuritis and symmetrical muscle wasting due to B1 deficiency

Sources of thiamine?

Beef, legumes, liver, milk

Which vitamin is Riboflavin?

What is the function of B2?

Cofactor FAD, FMN in succinate dehydrogenase reaction of TCA cycle (2ATP generation)

What are the consequences of B2 deficiency?

Cheilosis (lip thickening and fissures around corners) and corneal vascularization

Which vitamin is Niacin

Where is Niacin derived from?

Tryptophan

Which cofactors is Niacin part of

NAD, NADP

Which two vitamins are required for the synthesis of B3?

B2 and B6

What clinical issue is B3 used to correct?

Dyslipidemia (lowers VLDL, increases HDL)

What are the 3Ds of B3 deficiency (pellagra)

Dementia Diarrhea Dermatitis (rash around collar bone, Casal's necklace and sun exposed areas)

How can malignant carcinoid syndrome cause pellagra-like symptoms?

Increased metabolism of tryptophan so less B3 synthesis

What is Hartnup disease?

AR loss of neutral amino acid (tryptophan) transporters on enterocytes and rental tubule cells. Leads to amino aciduria, low tryptophan and thus B3 deficiency.

Treatment for Hartnup disease?

High protein diet and nicotinic acid supplement

How does isoniazid lead to B3 deficiency?

Decreases B6, which is needed to synthesize B3

What is the name for Vitamin B5?

Pantothenic acid

What is the function of B5

essential component for coenzyme A (Acyl CoA) and fatty acid synthase?

Symptoms of Vitamin B5 deficiency

enteritis, alopecia, dermatitis, adrenal insufficiency

Which vitamin is pyridoxine?

For which enzymes and reactions is B6 (PLP) a cofactor?

transaminations, carboxylations, and glycogen phosphorylase

Which neurotransmitters is B6 needed to synthesize?

Serotonin, epinephrine, norepinephrine, dopamine, GABA

What are the symptoms of B6 deficiency?

Convulsions, hyperirritability, peripheral neuropathy, sideroblastic anemia

Why does B6 deficiency lead to sideroblastic anemia?

Impaired heme synthesis and iron excess

Which drugs can induce B6 deficiency?

Isoniazid (suspect in TB patients) and oral contraceptives

Which vitamin is biotin?

Which enzymes is biotin a cofactor for?

Carboxylation enzymes (add 1C) Pyruvate carboxylase (3-->4) Acetyl-coA carboxylase Propionyl coA carboxylase

What can cause B7 deficiency?

Rare but either antibiotic use or excessive ingestion of raw egg whites (body builders)

Which vitamin is B9

Folate

What is the function of folate

THF--> 1c methylation in synthesis of DNA/RNA bases

What are the symptoms of folate deficiency

Macrocytic, megaloblastic anemia with hypersegmented polymorphonuclear cells; glossitis, no neuro symptoms

How do you distinguish between a folate deficiency vs B12 deficiency?

Folate deficiency has increased serum homocysteine and normal methylmalonic acid levels. B12 deficiency has elevated homocysteine and methylmalonic acid levels

Which two conditions commonly present with folate deficiency

alchoholism and pregnancy

Where is folate absorbed in GI tract

jejunum

Which drugs can cause folate deficiency

PMS: phenytoin, methotrexate, sulfonamides

Neural tube defects are often due to deficiency in which vitamin/

Folate

What is the major source of folate

leafy green vegetables

Which vitamin is Cobalamin

B12

How long does it take for body to deplete B12

Years

What is the major source of B12

animal products

What is the function of cobalamin (B12)

Cofactor for methionine synthase and methylmalonyl-coA mutase

Which antibodies are diagnostic of pernicious anemia?

anti-intrinsic factor (low B12)

What are the symptoms of folate deficiency?

Megaloblastic, macrocytic anemia; hypersegmented PMNs, parasthesias, subacute combined degeneration of dorsal columns and lateral corticospinal tracts and spinocerebellar tracts

What is the consequence of prolonged B12 deficiency?

Irreversible nerve damage

Which vitamin is ascorbic acid

Vitamin C

What are the 3 major functions of Vitamin C?

1. Facilitate iron absorption by reducing it to Fe2+ 2. Hydroxylation of proline and lysine in collagen synthesis (RER) 3. Dopamine beta-hydroxylase (DA --> NE)

What does vitamin C deficiency cause?

Scurvy: swollen, bleeding gums; bruising, petechiae, anemia, poor wound healing, corswcrew hair, weak immune system

What does Vitamin C excess cause?

N/V/D, fatigue, calcium oxalate nephrolithiasis; increased risk of iron toxicity in people with transfusions or hemochromatosis

What is a major manifestation of zinc deficiency?

acrodermatitis enteropathica (scaling, scathing rash around buttocks and genitalia)

What are symptoms of zinc deficiency

delayed wound healing, hypogonadism, decreased axillary, facial, pubic hair, anosmia

Which condition does protein malnutrition cause?

Kwarshiorkor

Clinical manifestation of Kwarshiorkor

Edema, anemia, fatty liver (small child with swollen abdomen)

What condition does total calorie malnutrition cause?

Marasmus-- muscle wasting, loss of subcutaneous fat.. emaciation

What are the three ways that alcohol is metabolized in liver?

1) Cytosol with Alcohol dehydrogenase (most common and robust) 2) Smooth ER with CYP2E1 3) Peroxisome with Catalase

What is alcohol converted to in the cytosol of hepatocytes by alcohol dehydrogenase?

Acetaldehyde

What do you gives someone with antifreeze (ethylene glycol) or methanol poisoning?

Fomepizole

How does fomepizole function?

Inhibits alcohol dehydrogenase

Which substances causes hangover symptoms?

Acetaldehyde accumulation

What is the limiting reagent in ethanol metabolism?

NAD+

How does Disulfiram interact with alcohol?

Inhibits acetaldehyde dehydrogenase, leads to hangover symptoms (nausea, vomiting, GI upset)

How does ethanol metabolism affect NADH/NAD ratio?

Increases it

What are the consequences in elevated NADH/NAD+

Lactic acidosis, fasting hypoglycemia, hepatosteatosis

How does ethanol lead to fasting hypoglycemia

elevated NADH/NAD+ favors OAA--> malate (prevents gluconeogenesis)

How does ethanol lead to hepatosteatosis (fatty liver)?

elevated NADH/NAD favors DHAP-->G3P

Which 5 metabolic reactions take place in the mitochondria

beta-oxidation (fatty acid oxidation), acetyl-coA production, TCA cycle, oxidative phosphorylation, ketogenesis

Which 6 metabolic processes take place in the cytoplasm?

Glycolysis, HMP shunt, synthesis of steroids (SER), proteins, fatty acids, cholesterol and nucleotides

Which metabolic processes take place in both cytosol and mitochondria?

Heme synthesis, urea cycle, gluconeogenesis

What is the end product of galactose metabolism?

Glucose-1-phosphate

Elevated prolactin and hyperphenylalanemia suggest PKU due to which cofactor deficiency?

tetrahydrobiopterin (BH4)

Why does decreased BH4 lead to increased prolactin?

You have less dopamine being produced to inhibit prolactin

Which enzyme deficiency leads to porphyria cutanea tarda?

uroporhyrinogen decarboxylase (UROD)

What are the sympotoms of porphyria cutanea tarda?

recurrent blistering on back of hands and forearms, small itchy spots, hyperpigmentation after rupturing

Acute intermittent porphyria occurs with defect in which enzyme?

PBG deaminase

What is the typical presentation of acute intermittent porphyria?

woman with neuropsychiatric issues and abdominal pain

Which vitamin is required for activity of ALA synthase? (Heme synthesis)

Wild mushrooms contain a toxin that inhibits synthesis of which molecule?

messenger RNA (inhibit DNA Pol II)

Deficiencies of which vitamins is associated with hyperhomocysteinemia?

B6, B12, B9 (folate)

What is hyperhomocysteinemia associated with?

atherosclerosis and thrombotic events

Which urea cycle disorders are accompanied by hyperammonemia and excessive amounts of orotic acid?

Citrullinemia and ornithine transcarbamylase deficiency

Which vitamin deficiency can cause infertility and decrease serum phospholipids?

Vitamin E