Pennsylvania State University - NUTR 251

Lesson 8: Water-soluble Vitamins (Chapter 10)

General Questions

1)Distinguish between an enzyme, coenzyme, vitamin, substrate, and product.Name the water-soluble vitamins which are coenzymes and list their coenzyme names.

2. Describe the common characteristics of all vitamins. Then describe similarities and differences between fat- soluble and water-soluble vitamins. (Chpt 10, pg 304.) Are vitamins all organic molecules?

3. Review water-soluble vitamins in foods by doing the Activity, Let’s Go to Lunch, in Lesson 8. It is fair game to ask about these foods on a test.

Niacin, Thiamin, Riboflavin, Pantothenic Acid, and Vitamin B6

4. Why is beriberi a potential problem in populations which consume most of their kcals from “polished” rice? Americans eat lots of polished rice, yet do not get beriberi, why? What American subpopulation may be at risk for thiamin deficiency and why? Briefly describe the metabolic role of thiamin.

5. A group of rats were fed a diet with adequate amounts (about the RDA levels) of all essential nutrients except niacin (extremely low amounts). They grew just as well as the control rats that were fed all nutrients including niacin.

Explain why (hint: protein was adequate). Niacin is still considered an essential nutrient for humans. Why?

6. Pellagra was in epidemic proportions in this country around 1910-1930. What are the symptoms of this disease? What were the dietary conditions which precipitated this disease? What was the significance of a low protein diet? How did our public health officials resolve the situation so that pellagra is now eradicated in this country?

7. If you ate a nice lunch of steak and eggs, which provided 300 mg of tryptophan, how many milligrams of niacin equivalents did this meal provide? How does this compare to the RDA?

8. What nutrients are added to enriched grains? (Recommend rereading pages 45-53 describing differences between refined (and enriched) vs. whole grains.)

9. Describe in a brief sentence the roles of niacin (NADH) and riboflavin (FADH2) in ATP production.

10. Why is there a UL for niacin? (Lesson 8 and Chpt 10) Note that the UL reflects quantity in a supplement rather than niacin in food.

11. Why is there no pantothenic acid deficiency in the US? What is the role of pantothenic acids? That is, describe the importance of pantothenic acid in the conversion of pyruvate to acetyl CoA.

12. Biotin is needed to keep the TCA cycle going by making oxaloacetate from pyruvate as well as for other metabolic needs such as fatty acid metabolism. We get biotin from two sources; explain.

13. Vitamin B6  facilitates the release of energy like other B vitamins, but from protein rather than carbohydrates and fats. Explain.

14. Compare the RDA and UL for vitamin B6? Why is there a UL? Would you suggest a supplement of 100 mg/day of B6  to your sister who has PMS? Why or why not?

Folic Acid and Vitamin B12

15. What is the chemical name for vitamin B12. What does cobalt have to do with vitamin B12?

16. Explain the statement: Vitamin B12  deficiency causes a folate deficiency. What distinguishes pernicious anemia from megaloblastic anemia (i.e. folate deficiency)? Explain the roles of folate and B12  in blood health. Now describe vitamin B12’s second role in the body.

17. Explain the issue which prompted the Food and Drug Administration (FDA) in 1998 to approve the enrichment of flour (and other cereal products) with folic acid? What is neural tube defect? Why must women during their child bearing years (even before they are pregnant) be aware of their folate/folic acid intake? (Chpt 10 and p. 476-478) Since fortifying the food supply in the US, has the incidence of neural tube defect been reduced to zero? List foods rich in folate.

18. What is the connection between homocysteine and folate? Some hypothesize that the rate of heart disease may go down now that there is more folate in the food supply. Why? What other vitamins are connected to homocysteine metabolism? Note that no one believes that the RDA’s for these vitamins should be higher because of this heart disease connection, but rather to encourage RDA intakes of these vitamins as well as all vitamins by via foods is the recommendation.

19. Why are vegan vegetarians at risk for low B12  nutritional status?

20. Why does it take years to develop B12  deficiency and only weeks or months to produce folate deficiency?

21. What are the roles of gastric acid (HCl) and Intrinsic Factor (IF) in B12 absorption? Why are elderly at risk for B12  deficiency (pernicious anemia)? What is atrophic gastritis? What are some options on treating pernicious anemia in the elderly population?

Vitamin C

22. A person suffering from scurvy has pinpoint hemorrhaging in the skin and at points of the body where there is mechanical stress, like on the gums and joints. Why? Discuss the biological role of ascorbic acid and iron to explain this observation.