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. 25. Describe the functions of the three biotin-dependent carboxylases. Explain how each product affects metabolism. Pyruvate carboxylase converts pyruvate to oxaloacetate. Oxalacetate will enter the TCA cycle if ATP is needed; otherwise, it can participate in gluconeogenesis. Acetyl CoA Carboxylase forms malonyl CoA from acetate. This is the first step in fatty acid synthesis (lipogenesis). Propionyl Co-A carboxylase converts Propionyl-CoA to methylmalonyl-CoA. Methylmalonyl-CoA can be converted into succinyl Co for the TCA cycle. This enables metabolism of odd chain fatty acids. 26. How does biotin affect gene expression? How prevalent is this effect? Biotin binds to histones (proteins that package DNA); thus, altering DNA replication and transcription. >2000 genes use biotin for expression of cell signaling & cell cycle. 27. Why would consumers of raw eggs, but not cooked eggs, have the potential to become biotin deficient? In raw egg whites, the protein avidin is able to tightly bind biotin, thus preventing its absorption in the small intestine. However, when egg whites are cooked, this process denatures the avidin and prevents its binding to biotin, allowing for absorption. 8 - 11 eggs/day 28. What are the three major symptoms of biotin deficiency? Alopecia, inflammation of the eyelids, and nervous problems 29. Pantothenic Acid deficiency presents differently in various animal species. Name 3 ways deficiency presents in animals. Dermatitis in chicks, grey hair in rats, goose stepping in pigs, and anemia in ducks 30. List three reasons for an increased need of pantothenic acid. Describe the reasons why for each reason. Alcoholism (low intake), diabetes (increased excretion), inflammatory bowel disease (impaired absorption). 31. Why are the symptoms of pantothenic acid deficiency vague? What is the best known symptom? Because pantothenic acid deficiency is usually accompanied with other nutrient deficiencies. It is difficult to isolate and determine the symptoms related specifically to pantothenic acid. Burning foot syndrome. 32. What are the functions of coenzyme A, with regard to carbohydrate metabolism? oxidative decarboxylation of pyruvate oxidative decarboxylation of alpha-ketoglutarate 33. What populations are most at risk for Vitamin C deficiency? What is the amount of body stores at which symptoms appear? Populations most at ri Populations most at risk are - smokers, infants fed with evaporated or boiled milk, elderly (taking salicylates), those with low socio-economic status, (less access to fresh fruits & vegetables), malabsorption or cancer; 300 mg Vitamin C 34. What amount of vitamin C is needed to double iron absorption? What is an alternative way to increase absorption as well? 25 mg of vitamin C. 1 gram of meat tissue has the same effect as 1 mg Vitamin C. 35. Explain how vitamin C plays a role in carnitine synthesis. Give the role of carnitine and consequences of a deficiency Vitamin C reduces iron to regenerate it as a cofactor for enzymes involved in carnitine synthesis. Carnitine carries fatty acids into the mitochondria where they are oxidized to