Deck 9: Water-Soluble Vitamins

Question 1

Erythrocyte transketolase activity is an assay to assess the status of:

A) thiamin.
B) B₆.
C) riboflavin.
D) B₁₂.

Answer 1

A

Question 2

The most common tests of thiamin status include all the following EXCEPT:

A) static tests of urinary thiamin metabolites.
B) a static test of serum thiamin.
C) an in vitro functional test of RBC enzyme.
D) in vivo functional tests.

Answer 2

D

Question 3

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

Answer 3

A

Question 4

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.

Question 5

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 B₁₂

Question 6

A consequence of thiamin deficiency is:

A) pellagra.
B) megaloblastic anemia.
C) beriberi.
D) rickets.

Question 7

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

A) ferric
B) ferrous

Question 8

A major role for thiamin is:

A) energy transformation.
B) blood coagulation.
C) collagen formation.
D) erythrocyte synthesis.

Question 9

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

Question 10

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

Question 11

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

Question 12

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.

Question 13

The RDA for vitamin C for adult men is _____ and the UL is _____.

A) 75 mg, 500 mg
B) 100 mg, 500 mg
C) 90 mg, 2000 mg
D) 200 mg, 2000 mg

Question 14

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.

Question 15

Most animals synthesize their own ascorbic acid from _____.

A) glucose
B) glutamine
C) glycogen
D) alanine

Question 16

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.

Question 17

When ascorbic acid becomes dehydroascorbic acid it has _____.

A) lost 2 electrons
B) lost 1 electron
C) gained 2 electrons
D) gained 1 electron

Question 18

A primary function of vitamin C is to act as an:

A) antiviral agent.
B) antioxidant.
C) antirachitic agent.
D) acyl transferase.

Question 19

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

Question 20

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

Question 21

In the enzyme methionine synthase, vitamin B₁₂ 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

Question 22

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

Question 23

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 B₁₂

Question 24

Which of the following reflects long-term folate status?

A) serum folate
B) red blood cell folate
C) homocysteine concentration in blood
D) serum methylmalonic acid

Question 25

Riboflavin coenzymes remain bound to their enzymes during the oxidation-reduction reactions and the complexes are called _____.

A) apoenzymes
B) flavokinases
C) bound enzymes
D) flavoproteins

Question 26

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

Question 27

Which of the water-soluble vitamins is found widely distributed in all plant and animal foods, which makes a deficiency unlikely?

A) riboflavin
B) folic acid
C) pantothenic acid
D) pyridoxine

Question 28

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

Question 29

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) B₁₂ is a cofactor for utilization of the methyl group in the conversion of homocysteine to methionine.
D) More than one is false.

Question 30

350 39. Elevated homocysteine levels can be due to all the following EXCEPT:

A) low ascorbic acid.
B) low folacin.
C) low cobalamin.
D) low pyridoxine.

Question 31

Cheilosis is a symptom of a dietary deficiency of which vitamin?

A) niacin
B) ascorbic acid
C) riboflavin
D) biotin

Question 32

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, B₁₂, folate

Question 33

Synthesis of coenzyme A starts with the phosphorylation of which vitamin?

A) pyridoxal phosphate
B) pantothenic acid
C) vitamin E
D) folic acid

Question 34

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

A) phenylalanine
B) valine
C) tyrosine
D) tryptophan

Question 35

5-methyl THF requires the action of which vitamin in order to form THF?

A) B₁₂
B) B₂
C) niacin
D) C

Question 36

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

Question 37

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

Question 38

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

Question 39

350 40. 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

Question 40

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

A) thiamin
B) niacin
C) biotin
D) folic acid

Question 41

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) B₁₂

Question 42

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

Question 43

What amount of supplemental folic acid is recommended daily for women of childbearing age in the United States?

A) 200 ug DFE
B) 400 ug DFE
C) 600 ug DFE
D) 800 ug DFE

Question 44

Intrinsic factor is required for the majority of absorption of which vitamin?

A) C
B) B₆
C) B₁₂
D) B₂

Question 45

Which of the following would you find under B₁₂-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

Question 46

364 53. Vitamin B₆ 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

Question 47

A good source of vitamin B₆ is muscle meats because PLP is predominantly bound to the enzyme _____.

A) alanine aminotransferase
B) cystathionine synthase
C) glycogen phosphorylase
D) aspartic aminotransferase

Question 48

Because vitamin B₆ is involved in heme synthesis, a deficiency symptom is

A) hypochromic, microcytic anemia.
B) seizures.
C) hyperhomocysteinemia.
D) impaired calcium metabolism.

Question 49

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

Question 50

Which of the following vitamins has a Tolerable Upper Intake Level established?

A) thiamin
B) riboflavin
C) vitamin B₆
D) vitamin B₁₂

Question 51

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.

Question 52

B₆-dependent transamination reactions are important in which process?

A) glyconeogenesis
B) gluconeogenesis
C) heme synthesis
D) more than one of the above

Question 53

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

Question 54

Vitamin B₁₂ is absorbed in the _____.

A) duodenum
B) jejunum
C) ileum
D) colon

Question 55

Metabolism of vitamin B₆ to the primary coenzyme form, pyridoxal phosphate, requires the action of what other B vitamin?

A) GSH
B) NAD
C) THF
D) FMN

Question 56

Large amounts of folic acid can mask a vitamin B₁₂ deficiency and prevent _____ from resulting. Over time the symptoms unique to a vitamin B₁₂ 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

Question 57

Which vitamin is most involved in amino acid metabolism?

A) biotin
B) vitamin E
C) vitamin A
D) vitamin B₆

Question 58

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