Biochemistry - Nutrition Flashcards
Calcium homeostasis is associated with which fat-soluble vitamin?
Vitamin D
Clotting factor synthesis depends on which fat-soluble vitamin?
Vitamin K
Which fat-soluble vitamin acts as an antioxidant?
Vitamin E
Which groups of vitamins are water soluble?
B vitamins and Vit C
Is vitamin C fat soluble or water soluble?
Water soluble
Is thiamine fat soluble or water soluble?
Water soluble
Is riboflavin fat soluble or water soluble?
Water soluble
Is pantothenic acid fat soluble or water soluble?
Water soluble
Is cobalamin fat soluble or water soluble?
Water soluble
Are pyridoxine, pyridoxal, and pyridoxamine fat soluble or water soluble?
Water soluble
Is ascorbic acid fat soluble or water soluble?
Water soluble
Deficiency of which two water-soluble vitamins can cause macrocytic anemia?
Folate and Vit B12
Which water-soluble vitamin is associated with collagen synthesis?
Vitamin C (ascorbic acid)
Name two vitamins that serve as antioxidants.
Vitamin E and Vitamin C
Name the four fat-soluble vitamins.
ADEK
True or False? The absorption of fat-soluble vitamins depends on the pancreas as well as the gastrointestinal tract.
True; pancreatic lipases are necessary for absorption of fat-soluble vitamins
Is accumulation of fat- or water-soluble vitamins more likely to cause toxicity?
Fat
Name two malabsorption syndromes that can cause fat-soluble vitamin deficiencies.
Cystic fibrosis and sprue
Are the B-complex vitamins fat soluble or water soluble?
Water soluble
All of the water-soluble vitamins easily wash out from the body, except for which two?
Vitamin B12 and folate
In which organ is folate stored?
Liver
B-complex deficiencies often result in what three conditions?
Dermatitis, glossitis, and diarrhea
What is another name for vitamin A?
Retinol (remember Retinol is Vitamin-A, so think Retin-A)
What are the signs and symptoms of vitamin A deficiency?
Night blindness and dry skin
Vitamin A is a constituent of what visual pigment?
Retinal
What are the symptoms associated with vitamin A intoxication?
Arthralgias, fatigue, headaches, skin changes, sore throat, and alopecia
A man has recently been eating large amounts of liver. He presents with fatigue, hair loss, headache, and joint pains. What is your diagnosis?
Vitamin A excess
What foods contain high amounts of vitamin A?
Vitamin A is found in liver, and in leafy vegetables
Name two topical uses of vitamin A.
It can be used topically for wrinkles and for acne
What are the effects of taking large amounts of vitamin A during pregnancy?
It is a teratogen, and causes cleft palate and cardiac abnormalities
What is another name for vitamin B1?
Thiamine
Beriberi is caused by a deficiency of which vitamin?
Vitamin B1 (thiamine) (spell beriberi as Ber1Ber1)
Wernicke-Korsakoff syndrome is caused by a deficiency of which vitamin?
Vitamin B1 (thiamine)
Vitamin B1 is the precursor to what metabolic cofactor?
Thiamine pyrophosphate
What is the role of thiamine in the tricarboxylic acid cycle?
It is a cofactor for -ketoglutarate dehydrogenase
Which step in glycolysis requires thiamine?
Thiamine pyrophosphate is needed as a cofactor for pyruvate dehydrogenase
What vitamin is needed as a cofactor for branched-chain amino acid dehydrogenase?
Vitamin B1 (thiamine)
A known alcoholic presents with symptoms of muscle wasting and polyneuritis. What vitamin deficiency do you suspect?
Vitamin B1 (thiamine)
Are polyneuritis and muscle wasting characteristic of wet or dry beriberi?
Dry beriberi; wet beriberi is associated with high-output cardiac failure and edema
Why are alcoholics prone to beriberi and Wernicke-Korsakoff syndrome?
Malnutrition and malabsorption
An alcoholic patient in the emergency room has recent-onset ophthalmoplegia, confusion, and ataxia; you suspect what disease process?
Wernicke-Korsakoff syndrome
Why are the brain and heart susceptible to injury in thiamine deficiency?
Cells cannot generate adenosine triphosphate without thiamine and highly metabolically active cells are damaged first
What is another name for vitamin B2?
Riboflavin
Cheilosis and corneal vascularization occur as a result of a deficiency of which vitamin?
Vitamin B2(riboflavin) (remember: the 2 C;s)
What is cheilosis?
Inflammation of the lips, with scaling and fissures at the corners of the mouth; this is seen in vitamin B2 deficiency
Flavin adenine dinucleotide is derived from which vitamin?
Vitamin B2(riboflavin) (remember: FAD and FMN are derived from riboFlavin, B2 = 2ATP)
What is another name for vitamin B3?
Niacin
A deficiency of vitamin B3 (niacin) leads to what disease?
Pellagra
How can Hartnup disease lead to pellagra?
Through impaired absorption of tryptophan, which is used to synthesize niacin
How can malignant carcinoid syndrome lead to pellagra?
Through increased metabolism of tryptophan, which is used to synthesize niacin
How does isoniazid cause a niacin deficiency?
By depleting vitamin B6, the synthesis of niacin from tryptophan cannot occur
A patient being treated for hyperlipidemia complains of becoming red in the face after taking his medication; what drug is he taking?
He is likely on niacin, which at pharmacologic doses can cause facial flushing
What vitamin is the precursor of oxidized nicotinamide adenine dinucleotide and oxidized nicotinamide adenine dinucleotide phosphate?
Vitamin B3 (niacin) (remember: NAD derived from Niacin, B3 = 3 ATP)
What are the 3 D;s of pellagra?
Diarrhea, Dermatitis, and Dementia
True or False? In addition to diarrhea, dermatitis, and dementia, pellagra is also characterized by beefy glossitis.
True
True or False? Eating excess untreated corn can lead to pellagra.
True; vitamin B3 in corn is not absorbable unless treated
What is another name for vitamin B5?
Pantothenate
Pantothenate
Dermatitis, enteritis, alopecia, and adrenal insufficiency
What vitamin is a precursor of coenzyme A, a cofactor for acyl transfer?
Vitamin B5 (pantothenate) (remember: pantothen-A is in Co-A)
What vitamin is a component of fatty acid synthase?
Vitamin B5 (pantothenate)
Adrenal insufficiency may be caused by a deficiency of which vitamin?
Vitamin B5(pantothenate)
What is another name for vitamin B6?
Pyridoxine
What are the clinical features of vitamin B6 deficiency?
Convulsions, hyperirritability, peripheral neuropathy, and sideroblastic anemias
A deficiency of vitamin B6 is inducible by what two drugs?
Isoniazid and oral contraceptive pills
A 32-year-old man begins taking isoniazid after a positive purified protein derivative. He presents with numbness and tingling in the extremities. What is the most likely cause of his peripheral neuropathy?
Vitamin B6(pyridoxine) deficiency induced by INH
Which vitamin is the precursor to pyridoxal phosphate?
Vitamin B6 (pyridoxine)
Which vitamin is needed for transamination (alanine aminotransferase and aspartate aminotransferase) reactions?
Vitamin B6 (pyridoxine)
Which vitamin is needed for decarboxylation reactions?
Vitamin B6 (pyridoxine)
Which vitamin is needed as a cofactor for glycogen phosphorylase?
Vitamin B6 (pyridoxine)
What vitamin is required for conversion of tryptophan to niacin?
Vitamin B6 (pyridoxine)
Which vitamin is needed for heme synthesis?
Vitamin B6 (pyridoxine)
Which vitamin is required for the synthesis of niacin from tryptophan?
Vitamin B6 (pyridoxine)
What is another name for vitamin B12?
Cobalamin
What are the hematologic manifestations of vitamin B12deficiency?
Megaloblastic anemia
What are the neurologic manifestations of vitamin B12 deficiency?
Subacute combined degeneration, paresthesia, and optic neuropathy
Which vitamin transfers a methyl group to form methionine from homocysteine?
Vitamin B12 (cobalamin)
Which vitamin is needed for the conversion of methylmalonyl-CoA to succinyl-CoA?
Vitamin B12 (cobalamin)
In which organ is vitamin B12 stored?
The liver
If a person stopped all vitamin B12 intake, how long would it take to develop symptoms of deficiency?
Several years
What are dietary sources of vitamin B12?
Animal products
Pernicious anemia can cause vitamin ____ deficiency as a result of a lack of _____ _____.
B12; intrinsic factor
What medical conditions can lead to vitamin B12 deficiency?
Sprue enteritis, Diphyllobothrium latum infection, pernicious anemia, Crohn;s disease
What test is used to detect the cause of a deficiency of vitamin B12?
The Schilling test
What is the pathophysiology of the neurologic signs and symptoms of B12deficiency?
Synthesis of abnormal myelin
A 42-year-old woman with a history of gastric bypass surgery 5 years ago presents with visual disturbance and numbness in her fingers. She is found to have macrocytic anemia. What is the most likely cause of her symptoms?
Vitamin B12 deficiency
True or False? The neurologic sequelae of vitamin B12deficiency are easily reversible with vitamin supplementation.
False; a prolonged deficiency of cobalamin leads to irreversible nervous system damage
What is the most common vitamin deficiency in the United States?
Folic acid deficiency
What are the results of folate deficiency?
Macrocytic and megaloblastic anemias
What is the function of tetrahydrofolate?
It is a coenzyme for 1-carbon transfer/methylation reactions
What form of folate acts as a metabolic cofactor?
Tetrahydrofolate
Tetrahydrofolate is necessary for synthesis of what biological molecules?
Nitrogenous bases in DNA and RNA
True or False? Folic acid stores last for 5 years, so symptoms of depletion take a long time to develop after dietary insufficiency.
False; folate is not stored for very long
Supplemental folic acid is given during early pregnancy to reduce the incidence of _____ _____ _____.
Neural tube defects
What are dietary sources of folate?
Leafy greens (remember: FOLate from FOLiage)
Name 3 drugs that can cause a folic acid deficiency.
Methotrexate, phenytoin, sulphonamides
Compare and contrast symptoms of B12and folate deficiency.
There are no neurologic symptoms in folate deficiency
S-adenosylmethionine is formed from what two precursors?
Adenosine triphosphate and methionine
The regeneration of methionine and S-adenosylmethionine from homocysteine is dependent on which two vitamins?
Vitamin B12 and folate
What is the functional group involved in S-adenosylmethionine reactions?
S-adenosylmethionine tranfers methyl units (remember: S-adenosylmethioninethe methyl donor man)
What enzyme uses S-adenosylmethionine to create homocysteine from methionine?
Homocysteine methyltransferase
S-adenosylmethionine is required to synthesize which neurotransmitter?
Epinephrine
A deficiency of _____ may be caused by the use of antibiotics or the ingestion of raw eggs.
Biotin
What are the symptoms of biotin deficiency?
Dermatitis, enteritis, and alopecia
Biotin is required as a cofactor for _____ reactions.
Carboxylation (which add a 1-carbon group)
Biotin and pyruvate carboxylase catalyze what reaction?
Conversion of pyruvate to oxaloacetate
Biotin and acetyl-CoA carboxylase catalyze what reaction?
Conversion of acetyl-CoA into malonyl-CoA
Biotin and propionyl-CoA carboxylase catalyze what reaction?
Conversion of propionyl-CoA to methylmalonyl-CoA
What enzyme requires a biotin cofactor to create oxaloacetate?
Pyruvate carboxylase
What enzyme requires a biotin cofactor to create malonyl-CoA?
Acetyl-CoA carboxylase
What enzyme requires a biotin cofactor to create methylmalonyl-CoA?
Propionyl-CoA carboxylase
Biotin is bound by _____, which is found in egg whites.
Avidin (remember: AVIDin egg whites AVIDly binds biotin)
What is another name for vitamin C?
Ascorbic acid
What disease is caused by a deficiency of vitamin C?
Scurvy
A patient has swollen gums, bruising, anemia, and poor wound healing. What vitamin deficiency is probably responsible for these symptoms?
Vitamin C deficiency
List four symptoms that are associated with scurvy.
Swollen gums, bruising, anemia, and poor wound healing
Vitamin C is needed for the addition of _____ groups to the amino acids lysine and proline during collagen synthesis.
Hydroxyl
Vitamin C _____ (promotes/inhibits) iron absorption by keeping it in the _____ (reduced/oxidized) state, which is more absorbable
Promotes; reduced
True or False? Vitamin C is required for the conversion of dopamine to norepinephrine.
True
What are dietary sources of vitamin C?
Fruits and vegetables; British sailors carried limes to prevent scurvy (origin of the word limey)
What function does vitamin C share with vitamin E?
Both are antioxidants
What enzyme uses ascorbic acid to convert dopamine to norepinephrine?
Dopamine -hydroxylase
Is vitamin D2found in plants or produced in sun-exposed skin?
Vitamin D2 is found in plants
What is another name for vitamin D2?
Ergocalciferol
What form of vitamin D is found in vitamins and other pharmaceuticals?
Vitamin D2
Is vitamin D3found in plants or produced in sun-exposed skin?
Vitamin D3 is produced in sun-exposed skin
When drinking a glass of milk, what type of vitamin D are you absorbing?
Vitamin D3(remember: drinking milk (fortified with vitamin D) is good for bones)
What is another name for vitamin D3?
Cholecalciferol
What is the storage form of vitamin D?
25-OH D3
What is the active form of vitamin D3?
1,25(OH)2D3(calcitriol)
A deficiency of vitamin D causes what disease in children?
Rickets
A deficiency of vitamin D causes what disease in adults?
Osteomalacia
A deficiency of vitamin D may lead to ______ (hypocalcemia/hypercalcemia) and ______ (flaccid paralysis/tetany).
Hypocalcemia; tetany
Vitamin D increases the absorption of what two ions in the intestine?
Calcium and phosphorus
What is the effect of vitamin D on your bones?
Vitamin D increases bone resorption
A patient has hypercalcemia, loss of appetite, and stupor. What vitamin excess is probably responsible for these symptoms?
Vitamin D
In what disease do epithelioid macrophages convert vitamin D into its active form in excess, leading to hypercalcemia?
Sarcoidosis
A deficiency of vitamin E leads to the increased fragility of what cell type?
Red blood cells
What type of anaemia is seen in vitamin E deficiency?
Haemolytic anaemia
A patient presents with hemolytic anemia, muscle weakness, and neuropathy; what vitamin deficiency do you suspect?
Vitamin E
Vitamin K deficiency leads to _____ (increased/decreased/normal) prothrombin time, _____ (increased/decreased/normal) activated partial thromboplastin time, and _____ (increased/decreased/normal) bleeding time.
Increased, increased, normal (remember: K for Koagulation)
What is the cause of hemorrhagic disease of the newborn? How is it prevented?
The neonatal intestine is sterile and therefore cannot synthesize vitamin K; to prevent hemorrhage, all newborns are given a vitamin K injection at birth
Vitamin K is required for which anticoagulation factors?
Proteins C and S
Which clotting factors are dependent on vitamin K?
Factors II, VII, IX, and X and proteins C and S
What is the source of vitamin K for humans?
Vitamin K is synthesized by intestinal bacteria
What is the mechanism by which antibiotic use can cause vitamin K deficiency?
Destruction of intestinal bacteria, which synthesize vitamin K
What drug is a vitamin K antagonist?
Warfarin (coumadin)
A patient has delayed wound healing, hypogonadism, and decreased axillary, facial, and pubic hair. What nutritional deficiency is likely to be responsible for these symptoms?
Zinc deficiency
What dietary deficiency can exacerbate alcoholic cirrhosis?
Zinc
What are the symptoms of zinc deficiency?
Delayed wound healing; hypogonadism; decreased adult hair in the axilla, face, and pubic regions; dysgeusia; anosmia
What is the importance of zinc fingers?
Zinc fingers allow transcription factors and other molecules to interact with DNA
What is the limiting reagent in alcohol metabolism?
NAD+
What enzyme does disulfiram inhibit?
Acetaldehyde dehydrogenase
A patient taking fomepizole would have a decreased accumulation of _____ because it inhibits _____.
Acetaldehyde; alcohol dehydrogenase; fomepizole is used in cases of methanol poisoning
Where in the cell is the reaction that is inhibited by fomepizole?
Fomepizole blocks the action of alcohol dehydrogenase, which is in the cytosol
Where in the cell is the reaction that is inhibited by disulfiram?
Disulfiram inhibits acetaldehyde dehydrogenase, which is in the mitochondria
What happens to the rate of ethanol metabolism by alcohol dehydrogenase as more ethanol is consumed?
There is no change in the rate since this reaction proceeds by zero-order kinetics
Ethanol metabolism _____ (increases/decreases) the NADH/NAD+ratio in the liver, which _____ (promotes/inhibits) gluconeogenesis.
Increases; inhibits
Ethanol ingestion leads to the increased conversion of pyruvate to _____ and oxaloacetate to _____, because these reactions regenerate NAD+from NADH.
Lactate; malate
The high NADH/NAD+ ratio seen after ethanol ingestion is responsible for the shunting of metabolites away from _____ and toward _____ _____ synthesis.
Gluconeogenesis; fatty acid
Ethanol metabolism ultimately results in _____ as a result of the inhibition of gluconeogenesis, and hepatocellular _____ from increased fatty acid synthesis.
Hypoglycemia, steatosis
What by-product of ethanol metabolism is responsible for hepatic steatosis?
The accumulation of NADH drives pyruvate to lactate and oxaloacetate to malate, resulting in decreased gluconeogenesis and increased fatty acid synthesis
Kwashiorkor is the result of a deficiency of _____ in the diet.
Protein
A malnourished child is also anemic, edematous, and has elevated liver function tests; what is the diagnosis?
Kwashiorkor (remember: Kwashiorkor results from a protein-deficient MEAL: Malnutrition, Edema, Anemia, Liver (fatty))
What is the clinical picture of a patient with kwashiorkor?
Small child with swollen belly
Marasmus is the result of a deficiency of _____ in the diet.
Calories
A child presents with tissue and muscle wasting with loss of subcutaneous fat. Is she more likely to have kwashiorkor or marasmus?
Marasmus
A malnourished child has significant tissue wasting. Is she more likely to have kwashiorkor or marasmus?
Marasmus (remember: Marasmus results in Muscle wasting)
Kwashiorkor is a deficiency of _____ that results in skin lesions, anemia, edema, and liver malfunction (fatty change). By contrast, marasmus is a deficiency of _____ that results in tissue wasting.
Protein; calories
