Questions and Answers
When water-soluble vitamins are consumed in excess of body needs, generally the excess is ____.
A major function of B vitamins is to serve as ____.
Most animals synthesize their own ascorbic acid from ____.
When ascorbic acid becomes dehydroascorbic acid, it has ____.
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Vitamin C acts as a cofactor by maintaining iron in a reduced state in ____.
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The organ that is most commonly used as a storage site for B vitamins is the ____.
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Which water-soluble vitamin contributes to 'intracellular cement' in the formation of scar tissue and wound healing?
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The B vitamin that is involved in hematopoiesis (production of blood cells) is ____.
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Beriberi is a deficiency syndrome associated with ____.
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Without enough vitamin C, collagen would ____.
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A primary function of vitamin C is to act as an ____.
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Vitamin C's actual participation in biochemical reactions usually involves its antioxidant ability. Choose the description of this activity.
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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.
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The RDA for vitamin C for adult men is ____ and the UL is ____.
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In what way are water-soluble vitamins absorbed?
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A major role for thiamin is ____.
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Thiamin is important to fatty acid synthesis due to its requirement as a coenzyme for the pentose phosphate pathway enzyme ____.
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A consequence of thiamin deficiency is ____.
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Erythrocyte transketolase activity is an assay to assess the status of ____.
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Riboflavin is found most often in ____.
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FMN and FAD act as prosthetic groups for enzymes called ____.
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Cheilosis is a symptom of a dietary deficiency of which vitamin?
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When the diet is adequate in protein, the body can synthesize niacin from which amino acid?
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The best sources of niacin are ____.
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Which classical vitamin deficiency is known for the four Ds: dermatitis, dementia, diarrhea, and death?
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Which of the water-soluble vitamins is found widely distributed in all plant and animal foods, which makes a deficiency unlikely?
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Synthesis of coenzyme A starts with the phosphorylation of which vitamin?
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Hair loss associated with eating raw eggs may be reversed by treatment with ____.
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Decarboxylation of pyruvate is achieved by the interaction of pantothenic acid with thiamin, riboflavin, and ____.
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A deficiency of which vitamin is associated with these symptoms: hallucinations, lethargy, skin rash, alopecia, and muscle pain?
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Folate in foods can only be absorbed in the monoglutamate form; therefore, digestive enzymes called ____ are important for folate nutriture.
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Consumption of raw eggs causes a biotin deficiency due to the binding of ____ to the biotin, thus preventing its absorption.
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Folate's discovery resulted from the search to cure ____.
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Which of the following reflects long-term folate status?
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The degradation of ____ provides the majority of one-carbon groups for pyrimidine synthesis. In this process, ____ is formed.
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Methylation of DNA influences gene expression. Which vitamin is important in this process?
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Folate and ____ participate in the regeneration of methionine from homocysteine.
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5-methyl THF requires the action of which vitamin in order to form THF?
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Burning foot syndrome may be caused by a deficiency of ____.
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Methionine is used to synthesize S-adenosylmethionine (SAM). This is important so that ____.
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Folate is vitally important for dividing cells during growth and cancer because of its essential role in the synthesis of ____.
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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 ____.
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The last vitamin to be discovered was ____.
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A cobalt deficiency may lead to ____.
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Intrinsic factor is required for the majority of absorption of which vitamin?
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Vitamin B12 is absorbed in the ____.
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Pyridoxine is found almost exclusively in ____.
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Free pyridoxine is yielded by the action of ____.
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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 ____.
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Which vitamin is most involved in amino acid metabolism?
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Pellagra symptoms may appear during B6 deficiency because this vitamin is required in the process of obtaining niacin from tryptophan.
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Water-soluble vitamins are not stored, but readily excreted-the one exception is that we can store folate in the liver.
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Pernicious anemia can be due to folate or B12 deficiency.
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Fish are a major source of thiamin.
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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.
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High circulating levels of homocysteine (i.e., hyperhomocysteinemia) have been implicated in a number of pathologies including cardiovascular disease.
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Biotin appears to be a very safe vitamin supplement as there has been no toxicity reported from oral biotin ingestion nor is there a Tolerable Upper Intake Level established.
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Increases in plasma holotranscobalamin TCII concentrations provide an indication of vitamin B12 absorption.
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Impaired folding and secretion of proteins have been observed with thiamin deficiency.
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Abnormally high urinary excretion of xanthurenic acid may be an indication of niacin deficiency.
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An example of a cleavage reaction requiring PLP is the degradation of thiamin into its pyrimidine and thiazole moieties.
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Initial research on vitamin B6 was aimed at correcting dermatitis in rats.
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Vitamin C's antioxidant abilities may inhibit high-density lipoprotein (HDL) oxidation, which may diminish plaque formation associated with heart disease.
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Most thiamin in the American diet comes from products that have been enriched.
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Large doses of nicotinic acid are used to treat certain types of hyperlipidemias.
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Nutrients can be used to compensate for some gaps in our DNA. For example:
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How do we know that folate fortification has improved the biochemical folate status of Americans?
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What is the criterion for a genetic difference to be called a 'polymorphism'?
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Folic acid fortification has ____.
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Study Notes
Water-Soluble Vitamins Overview
- Water-soluble vitamins are quickly absorbed into the portal blood system and excess is primarily excreted in urine.
- B vitamins often function as parts of coenzymes, necessary for various metabolic processes.
- The liver serves as the main storage location for water-soluble vitamins, excluding ascorbic acid (Vitamin C).
Vitamin C (Ascorbic Acid)
- Vitamin C is synthesized in most animals from glucose.
- Conversion of ascorbic acid to dehydroascorbic acid involves the loss of two electrons.
- Key functionalities include acting as a cofactor in collagen synthesis and functioning as an antioxidant by donating electrons to reduce mineral cofactors.
- Adequate intake is crucial for energy production and for preventing underhydroxylation of collagen.
- Recommended daily allowance (RDA) for adult men is 90 mg, with a tolerable upper intake level (UL) of 2,000 mg.
B Vitamins Functionality
- Thiamin (Vitamin B1) is crucial for energy production and fatty acid synthesis, utilizing the enzyme transketolase.
- Vitamin B12 is involved in hematopoiesis and requires intrinsic factor for absorption, primarily occurring in the ileum.
- Niacin (Vitamin B3) is derived from tryptophan and is essential in preventing the four D's: dermatitis, dementia, diarrhea, and death in deficiency.
- Biotin (Vitamin B7) deficiency can occur due to raw egg consumption, caused by avidin binding.
- Folate (Vitamin B9) is critical for DNA synthesis, influencing cell division and requiring digestive enzymes for absorption.
Deficiency Syndromes
- Deficiency of Vitamin B1 leads to beriberi.
- Symptoms of biotin deficiency include hallucinations, skin rash, and hair loss; treatable with biotin supplementation.
- Vitamin B12 deficiency causes megaloblastic macrocytic anemia, alongside neurologic symptoms.
- Pellagra is associated with niacin deficiency, characterized by the four D's.
Folate and Genetic Factors
- Folate plays a vital role in the regeneration of methionine from homocysteine.
- It is essential for the synthesis of purines and pyrimidines, which are crucial for cell division, particularly during growth or malignancy.
- Genetic polymorphisms affecting folate metabolism can result in elevated plasma homocysteine levels.
Research and Recommendations
- Dietary fortification of folate has significantly reduced neural tube defects (NTDs) in the population.
- Long-term folate status is best reflected through red blood cell folate levels.
- Most thiamin in the U.S. diet comes from enriched products, indicating a reliance on processed foods for this nutrient.
- Ongoing research continues to establish the relationship between nutrient supplementation and the prevention of deficiencies or related disease outcomes.
Studying That Suits You
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Description
Test your knowledge on water-soluble vitamins with this quiz based on Chapter 9. You'll explore key functions, storage, and processing of B vitamins and others. Review important concepts to ensure a thorough understanding of dietary nutrients essential for health.