Final: L1-Ch. 9 Flashcards by leah Unknown

When water-soluble vitamins are consumed in excess of body needs, generally the excess is:

a. excreted in the feces.
b. stored in liver, bone, and adipose tissue.
c. excreted in the urine.
d. not absorbed.

c. excreted in the urine.

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A major function of B vitamins is to serve as:

a. antibodies.
b. a source of energy.
c. a part of a coenzyme.
d. electrolytes.

c. a part of a coenzyme.

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Most animals synthesize their own ascorbic acid from _____.

a. glucose
b. glutamine
c. glycogen
d. alanine

a. glucose

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When ascorbic acid becomes dehydroascorbic acid it has _____.

a. lost 2 electrons
b. lost 1 electron
c. gained 2 electrons
d. gained 1 electron

a. lost 2 electrons

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Vitamin C acts as a cofactor by maintaining iron in a reduced state in:

a. collagen synthesis.
b. methylation of homocysteine.
c. release of energy from nutrients.
d. red blood cell synthesis.

a. collagen synthesis.

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Although excess absorbed ascorbic acid is excreted in urine, the body has an estimated maximal body pool of about _____, which can be maintained with intakes of 100-200 mg vitamin C per day.

a. 500 mg
b. 1000 mg
c. 1500 mg
d. 2000 mg

d. 2000 mg

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Which water-soluble vitamin contributes to “intracellular cement” in the formation of scar tissue and wound healing?

a. thiamin
b. riboflavin
c. vitamin C
d. vitamin B 12

c. vitamin C

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Which of the following molecules synthesized with the help of vitamin C underscores the importance of vitamin C to fat metabolism?

a. carnitine
b. collagen
c. tyrosine
d. norepinephrine

a. carnitine

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Ascorbic acid provides a reducing equivalent so that iron is in the _____ form
in lysyl hydroxylase.

a. ferric
b. ferrous

b. ferrous

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Without enough vitamin C, collagen would _____.
a. be too tightly coiled
b. be over-hydroxylated
c. be under-hydroxylated
d. too strong and less flexible

c. be under-hydroxylated

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A primary function of vitamin C is to act as an:
a. antiviral agent.
b. antioxidant.
c. antirachitic agent.
d. acyl transferase.

b. antioxidant.

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Vitamin C’s actual participation in biochemical reactions usually involves its
antioxidant ability. Choose the description of this activity.

a. Donates an electron or electrons to oxidize a mineral cofactor
b. Accepts an electron or electrons to reduce a mineral cofactor
c. Donates an electron or electrons to reduce a mineral cofactor
d. Accepts an electron from the quinone form of vitamin E

c. Donates an electron or electrons to reduce a mineral cofactor

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The necessity of ascorbic acid for its role in _____ is believed to be the reason that people with scurvy have no energy and are very tired.

a. collagen synthesis
b. creatine synthesis
c. hormone activation
d. carnitine synthesis

d. carnitine synthesis

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Ascorbic acid may act as a pro-oxidant by:

a. reducing ferrous iron.
b. mobilizing ferric iron from storage.
c. reacting with transferrin-bound iron.
d. reducing dehydroascorbic acid.

b. mobilizing ferric iron from storage.

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A major role for thiamin is:

a. energy transformation.
b. blood coagulation.
c. collagen formation.
d. erythrocyte synthesis.

a. energy transformation.

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Thiamin is important to fatty acid synthesis due to its requirement as a

coenzyme for the pentose phosphate pathway enzyme _____.

a. dopamine monooxygenase
b. transketolase
c. alpha-ketoglutarate dehydrogenase
d. phenylalanine hydroxylase

b. transketolase

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A consequence of thiamin deficiency is:

a. pellagra.
b. megaloblastic anemia.
c. beriberi.
d. rickets.

c. beriberi.

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Erythrocyte transketolase activity is an assay to assess the status of:
a. thiamin.
b. B 6 .
c. riboflavin.
d. B 12 .

a. thiamin

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When the diet is adequate in protein, the body can synthesize niacin from which amino acid?

a. phenylalanine
b. valine
c. tyrosine
d. tryptophan

d. tryptophan

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Which vitamin has a reduced coenzyme form important for fatty acid and cholesterol synthesis that is a product of the pentose phosphate pathway?

a. niacin
b. thiamin
c. riboflavin
d. vitamin C

a. niacin

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Which classical vitamin deficiency is known for the four Ds: dermatitis, dementia, diarrhea, and death?

a. thiamin
b. niacin
c. biotin
d. folic acid

b. niacin

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Which three vitamins are involved in the synthesis of fatty acids?

a. biotin, vitamin D, thiamin
b. thiamin, riboflavin, niacin
c. niacin, biotin, pantothenic acid
d. riboflavin, B 12 , folate

c. niacin, biotin, pantothenic acid

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Biotin must be covalently bound to each of four different enzymes in order for them to carry out _____.

a. decarboxylations
b. oxidation-reduction reactions
c. transfer of acetate groups
d. carboxylations

d. carboxylations

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A deficiency of what vitamin is associated with these symptoms: hallucinations, lethargy, skin rash, alopecia, and muscle pain?

a. biotin
b. thiamin
c. vitamin C
d. vitamin B 12

a. biotin

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Folate in foods can only be absorbed in the monoglutamate form; therefore, digestive enzymes called _____ are important for folate nutriture. a. hydrolases b. lipases c. conjugases d. legumes

c. conjugases

To absorb folate consumed from green, leafy vegetables, _____. a. phosphate groups much be removed by the action of alkaline phosphatase b. glutamate must be transaminated to form alpha-ketoglutarate c. glutamic acid molecules must be removed d. glutamic acid molecules must be added

c. glutamic acid molecules must be removed

33. Carbon in the one-carbon pool can be in the 5-methyl- THF form or the 5,10-methylene-THF form. Which statement is FALSE? a. Both forms of carbon (methyl and methylene) can be used directly for thymidylate synthesis. b. The methylene group of 5,10-methylene- THF can be oxidized to generate 5-methyl- THF and vice versa. c. B 12 is a cofactor for utilization of the methyl group in the conversion of homocysteine to methionine. d. More than one is false.

d. More than one is false.

The degradation of _____ provides the majority of one-carbon groups for pyrimidine synthesis. In this process _____ is formed. a. methionine, tetrahydrofolate b. serine, 5,10-methylene tetrahydrofolate c. uridine, tetrahydrofolate d. homocysteine, 5-methyl tetrahydrofolate

b. serine, 5,10-methylene tetrahydrofolate

In the enzyme methionine synthase, vitamin B 12 acts by accepting a _____ group from _____ and donating this group to _____ to form methionine. a. carbon, methionine, folate b. methyl, 5-methyltetrahydrofolate, homocysteine c. methyl, formiminoglutamic acid, succinyl-CoA d. carbon, serine, glycine

b. methyl, 5-methyltetrahydrofolate, homocysteine

Which is NOT a fate of homocysteine in the cell? a. methylated to methionine b. used to restore tetrahydrofolate c. used to synthesize cysteine d. used in the synthesis of leucine

d. used in the synthesis of leucine

5-methyl THF requires the action of which vitamin in order to form THF? a. B 12 b. B 2 c. niacin d. C

a. B 12

Elevated homocysteine levels can be due to all the following EXCEPT: a. low ascorbic acid. b. low folacin. c. low cobalamin. d. low pyridoxine.

a. low ascorbic acid.

Methionine is used to synthesize S-adenosylmethionine (SAM). Why is this important? a. so that 5-methyl THF is formed b. so that dUMP is catalyzed to dTMP c. so that fatty acids with an odd-numbered chain can be metabolized d. so that methyl groups are available

d. so that methyl groups are available

Folate is vitally important for dividing cells during growth and cancer because of its essential role in the synthesis of _____. a. lipid bilayers b. mitochondria c. lysosomes and peroxisomes d. purines and pyrimidines

d. purines and pyrimidines

Tetrahydrofolate is vitally important for dividing cells during growth and cancer and knowledge of this need is used in cancer treatment by giving the drug methotrexate to inhibit the enzyme _____. a. folylpolyglutamate synthetase b. dihydrofolate reductase c. formimino glutamate d. conjugase

b. dihydrofolate reductase

Which of the following would you find under B 12 -deficient conditions and the methyl trap hypothesis? a. accumulation of 5-methylene THF b. depletion of homocysteine c. accumulation of THF d. accumulation of 5-methyl THF e. more than one of the above

d. accumulation of 5-methyl THF

Intrinsic factor is required for the majority of absorption of which vitamin? a. C b. B 6 c. B 12 d. B 2

c. B 12

Vitamin B 12 is absorbed in the _____. a. duodenum b. jejunum c. ileum d. colon

c. ileum

The normal digestion and absorption of cobalamin requires adequate protein digestion in the stomach; the presence of 2 nonenzymatic proteins: _____; and a receptor located in the _____. a. R binders and hydrochloric acid, colon b. pepsin and hydrochloric acid, ileum c. R protein and intrinsic factor, ileum d. R protein and intrinsic factor, duodenum

c. R protein and intrinsic factor, ileum

Which of the water-soluble vitamins is able to be stored and retained in the body for long periods of time? a. folic acid b. niacin c. thiamin d. B 12

d. B 12

Large amounts of folic acid can mask a vitamin B 12 deficiency and prevent _____ from resulting. Over time the symptoms unique to a vitamin B 12 deficiency will occur, and these are related to the _____. a. microcytic anemia, muscular system b. DNA and RNA synthesis, vascular system c. one-carbon transfer, nervous system d. macrocytic anemia, nervous system

d. macrocytic anemia, nervous system

Which vitamin is most involved in amino acid metabolism? a. biotin b. vitamin E c. vitamin A d. vitamin B 6

d. vitamin B 6

Metabolism of vitamin B 6 to the primary coenzyme form, pyridoxal phosphate, requires the action of what other B vitamin? a. GSH b. NAD c. THF d. FMN

d. FMN

A good source of vitamin B 6 is muscle meats because PLP is predominantly bound to the enzyme _____. a. alanine aminotransferase b. cystathionine synthase c. glycogen phosphorylase d. aspartic aminotransferase

c. glycogen phosphorylase

Vitamin B 6 functions importantly in all of the following EXCEPT _____. a. transamination of amino acids b. synthesis of fatty acids c. synthesis of niacin d. glycogen breakdown

b. synthesis of fatty acids

Because vitamin B 6 is involved in heme synthesis, a deficiency symptom is a. hypochromic, microcytic anemia. b. seizures. c. hyperhomocysteinemia. d. impaired calcium metabolism.

a. hypochromic, microcytic anemia.

Ascorbic acid can reduce the oxidized form of vitamin E. Choose the phrase that describes this. a. Ascorbic acid reduces the tocopheroxy radical to the quinone form; ascorbic acid is oxidized to dehydroascorbic acid. b. Ascorbic acid reduces the hydroquinone form to the quinone form; ascorbic acid is reduced to semi-dehydroascorbic acid. c. Ascorbic acid reduces the tochopheroxy radical to the tocopherol form; ascorbic acid is oxidized to semi-dehydroascorbate.

c. Ascorbic acid reduces the tochopheroxy radical to the tocopherol form; ascorbic acid is oxidized to semi-dehydroascorbate.

B 6 -dependent transamination reactions are important in which process? a. glyconeogenesis b. gluconeogenesis c. heme synthesis d. more than one of the above

b. gluconeogenesis

PLP functions as a coenzyme for _____ when alanine enters the liver. Alanine becomes its α-keto acid, _____. a. transamination, pyruvic acid b. transamination, α-ketoglutaric acid c. transmethylation, histidine d. desulfation, methioninie

a. transamination, pyruvic acid

T/F Pellagra symptoms may appear during B 6 deficiency, because this vitamin is required in the process of obtaining niacin from tryptophan.

True

T/F Water-soluble vitamins are not stored, but readily excreted—the one exception is that we can store folate in the liver.

False Explanation: The exception is not folate, but B 12 ¸which can be stored in the liver.

T/F Pernicious anemia can be due to folate or B 12 deficiency.

False Explanation: Pernicious anemia refers to megaloblastic anemia owing to lack of intrinsic factor.

T/F The active form of a vitamin is usually the form that has the greatest bioavailability.

Explanation: Opposite—usually the active form must be modified to its parent form for absorption (e.g., TPP to thiamin; THF polyglutamates to monoglutamate).

T/F The primary role of vitamin C is as a reducing agent, particularly for the mineral component of a number of enzymes that becomes oxidized following catalysis of a reaction.

True

T/F High circulating levels of homocysteine (i.e., hyperhomocysteinemia) have been implicated in a number of pathologies including cardiovascular disease.

True

T/F The reason we use equivalents when discussing the RDA for some vitamins is that there are different forms of the vitamin that, by weight, are not equal in terms of vitamin activity—this is due to differences in absorption and/or metabolism.

True

T/F Circulating concentrations of a vitamin typically reflect diet, whereas intracellular (e.g., RBCs, leukocytes) concentrations reflect body pools.

True

T/F An increase in blood pyruvate and lactate levels may be due to a deficiency of riboflavin. Explanation: Thiamin, not riboflavin.

False Explanation: Thiamin, not riboflavin.

T/F Urinary excretion of xanthurenic acid may be an indication of niacin deficiency. Explanation: PLP, not niacin.

False Explanation: PLP, not niacin.

T/F Biotin and B 12 are both required for the synthesis of odd-chain fatty acids.

False Explanation: They are both required for the oxidation, not synthesis, of odd-chain FA

T/F In the folate-dependent one-carbon pool, a carbon unit in the methyl form (i.e., 5-methyl THF) is used in the conversion of homocysteine to methionine, whereas a carbon unit in the methylene form (i.e., 5,10-methylene THF) is used in DNA synthesis.

True

T/F Vitamin C is a good reducing agent, meaning it keeps things reduced by undergoing irreversible oxidation; thus, it must continuously be replaced by dietary sources.

False Explanation: It’s oxidation is not irreversible—it can be recycled back to its reduced form.

Name the enzyme and function of the following coenzyme: Thiamin Diphosphate

pyruvate dehydrogenase; important for decarboxylations in carbohydrate catabolism

Name the enzyme and function of the following coenzyme: Flavin Adenine Dinucleotide

glutathione reductase; important for red blood cell antioxidant integrity and a sensitive measure of riboflavin nutriture

Name the enzyme and function of the following coenzyme: Nicotinamide Adenine Dinucleotide

aldehyde dehydrogenase; important for catabolism of vitamin B 6 (pyridoxal to pyridoxic acid)

Name the enzyme and function of the following coenzyme: Biotin

acetyl-CoA carboxylase; important to form malonyl-CoA and commit acetyl-CoA to fatty acid synthesis

Name the enzyme and function of the following coenzyme: Pyridoxal Phosphate

alanine aminotransferase; important in amino acid transaminations for facilitating protein synthesis

Phrase: Hypochromic, microcytic anemia Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin B6

Phrase: Serine hydroxymethyltransferase Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin B6

Phrase: Edema and cardiac insufficiency Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- None of These

Phrase: Hemoglobin synthesis Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin B6

Phrase: Prolyl hydroxylase Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin C

Phrase: Latin word means "leaf"; italian word means "foliage" Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Folate or Folic Acid

Phrase: PLP coenzyme form Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin B6

Phrase: Broccoli and potatoes are good sources Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin C

Phrase: coenzyme carries one-carbon groups in metabolism Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Folate or Folic Acid

Phrase: pernicious anemia is a lack of absorption of this Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin B12

Phrase: gulonolactone oxidase Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin C

Phrase: coenzyme labilizes covalent bonds around the alpha- carbon of an amino acid Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin B6

Phrase: a water-soluble vitamin that is not a coenzyme Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Vitamin C

Phrase: a vitamin whose supplement form has MORE biologic action than the form found in nature Choices: - Vitamin B12 - Vitamin B6 - Folate or Folic Acid - Vitamin C - None of These

- Folate or Folic Acid