NTR 343 Final Exam Quiz Bank 2022

NTR 343 Final Exam Quiz Bank 2022 1. All of the following B vitamins are involved in oxidative decarboxylation of pyruvate except: c. Folate 2. Explain in scientific detail how certain foods can inhibit the absorption of thiamin. List four food examples. Some foods contain thiaminases which break the weak methylene bridge between the two rings in the thiamin structure. Example foods are raw fish, tea, shrimp, mussels, clams, fish paste, betel nuts, ferns 3. Which of the following is not a function of thiamin? c. Synthesis of FADH2 5. What is the Tolerable Upper Level of thiamin? Why was this amount established.? There is none, as it would not occur from diet. 6. Name and explain three exceptions of vitamins that do not have to be provided for in the diet. Vitamin D: synthesized in skin by high energy radiation Vitamin K: synthesized in gut by intestinal flora Niacin: converted from tryptophan in tissues Choline: synthesized in metabolism 7. Why is milk kept in a cardboard or opaque container? Milk is kept in opaque containers because the riboflavin that is found abundantly in milk is unstable and easily destroyed when exposed to UV light 8. Explain the role of FAD in the restoration of glutathione to its active form. FAD is the coenzyme for glutathione reductase; it adds hydrogens to the oxidized form of glutathione to create the reduced form that is active. 9. A dietary staple of cornbread led to pellagra in the southern United States, yet a dietary staple of corn tortillas did not cause a deficiency in niacin. Explain the scientific reason for this. Niacin in the corn meal of cornbread is bound to a protein, so the vitamin is not available. Corn tortillas are made from corn meal that has subject to alkaline hydrolysis (cooking in lime water or CaOH) to make masa harina (the ingredient for tortillas). This process liberates the niacin (and creates the ability to make a tortilla from meal that sticks together). 11. What are the differences between the functions of NAD and NADP? Be specific NAD is needed for energy metabolism (Including glycolysis, oxidative decarboxylation of pyruvate, oxidation of acetyl CoA, beta oxidation of fatty acids, and oxidation of ethanol) while NADP is needed for synthesis of fats, cholesterol, and steroid synthesis. 12. Explain why B6 supplements can cause toxicity. How does this compare to Vitamin B12? B6 supplements are in the form of pyridoxine, which is a competitive inhibitor of the active enzyme, pyridoxal phosphate. Additionally, an excess of B6 and a deficiency of Vitamin B12, can both cause neuropathy. 13. Explain the function of Delta-6-Desaturase and how it is related to a B vitamin. It is a PLP-dependent enzyme that metabolizes both omega 6 and omega 3 fatty acids to 20 carbon compounds by desaturation of linolenic and gamma-linolenic acid. 14. List three food sources of Vitamin B6 . Is it present in enriched flour? Explain why or why not. Meat, Poultry, Fish, and Starchy Vegetables. It is not in enriched flour because it is found in many foods and requirements can be reached within an adequate diet. 15. List four inhibitors of the digestion of folate alcohol, acidic environment, cabbage, zinc deficiency, legumes, oranges pick four 16. Name and explain the role of micronutrients required for folate digestion and activation. Zinc is required for digestion as it shortens the polyglutamate tail of folate from foods to form the monoglutamate form that can be absorbed. Vitamin B12 is required for activation; folate is inactive in its methylated form, and B12 is used to remove the methyl group. 17. Explain the dual role of folate in cancer development. How is this related to the tolerable upper limit? Low folate intake protects against early carcinogenesis. But high folate intake can promote advanced carcinogenesis. High levels of folate (1000 mg/d) increased the risk of advanced colorectal lesions; so the upper limit is 1000 mg (1 mg). 18. Where was folate given as a supplement by the Public Health Service in the United States? Why? The Rio Grande Valley. This area has had a high incidence of neural tube defects. Although it could have a multifactorial etiology, this may have been a consequence of folate deficiency in some pregnant women. 19. What age group is most likely to have a vitamin B12 deficiency and why? The elderly (>50 years) because they secrete less acid and less intrinsic factor and may have used proton pump inhibitors that reduce acid secretion for >2 yrs. 20. Why is vitamin B12 deficiency almost nonexistent among vegans in third world countries than vegans in developed countries? The sanitation process of root vegetables sold in third world countries does not fully remove the dirt from all the vegetables, and the dirt has fecal material which contains bacteria that produce vitamin B12. 21. Explain how choline can contribute to the prevention of cardiovascular disease. Choline can be oxidized to betaine in the liver. Betaine can then function as a methyl group donor to homocysteine by the action of a methyltransferase enzyme generating methionine. Reduction of homocysteine levels lowers the risk for health disease and stroke. 22. A patient is suspected to have a choline toxicity. What would the symptoms, and likely be the cause of the toxicity? The patient may have a fishy body odor, vomiting, salivation, sweating, decreased blood pressure, or tinnitus. Deficiency would likely be due to use of supplements. 23. Why is choline a "conditionally essential" vitamin? Humans are capable of producing choline from glycine. Yet there is an RDI for choline because it is important for fetal development during pregnancy.