Chapter 10 Reading Guide
*We will skip section “B vitamin roles” for now. We will revisit that section in chapter 7.
1. List the water-soluble and the fat-soluble vitamins.
2. What are some factors that affect vitamin bioavailability?
3. Can certain vitamins be degraded by heat, light or oxygen?
4. Compare/contrast the absorption, transit, excretion and storage of water-soluble vs. fat-soluble vitamins
5. What is a coenzyme?
6. For each of the B vitamins,
a. Name the coenzyme they are part of
b. List the general functions of the above coenzyme (do NOT describe the specific functions that refer back to chapter 7; the book will note when this is the case)
c. Name and describe symptoms of deficiency diseases
d. Describe toxicity symptoms, if they are known
e. List several good food sources
f. When appropriate (ie, when the book does so), talk about commonness of deficiency in the US today; for example, thiamin deficiencies are very rare in the general population, but more common in alcoholics.
7. Why are B-vitamins needed in order for cells to have energy, even though vitamins don’t actually provide any energy directly?
8. From what amino acid can niacin be made?
9. Describe the role of PLP in nonessential amino acid synthesis and niacin synthesis
10. Where is B6 stored in the body?
11. What B vitamin activates folate?
12. How is folate related to reduced risk of heart disease?
13. What are 2 over the counter drugs that (when taken in large amounts for extended periods) can interfere with folate?
14. Describe the absorption of vitamin B12.
15. Why does B12 deficiency often occur in people with adequate intake?
16. Do B12 deficiencies show up quickly (within weeks) or slowly (months to years)? Why?
17. How are folate and B12 related, and why can folate supplements be dangerous if you have a B12 deficiency?
18. What cooking method preserves most vitamins, but destroys B12?
19. Describe the anemia caused by B12 and folate deficiencies (ie, describe what actually happens with red blood cells).
*Please refer back to my chapter 6 supplemental lectures for extra information about B12
20. List 3 substances that are required from food in small amounts, and whose status’ as vitamins is debated. Why are supplements of these unnecessary? * You do not need to fill out your B-vitamin chart for these; this is all you need to know about them (their names).
21. Are vitamin B toxicities from food alone likely? Explain.
22. Can you obtain enough B vitamins from food alone? Explain.
23. Why are vitamin (and mineral) deficiencies so far-reaching in their effects?
24. Why is it often likely for a person who has one vitamin/mineral deficiencies to have other deficiencies?
25. What is the chemical name of vitamin C?
26. List and briefly describe the roles of vitamin C.
27. Describe the symptoms of vitamin C deficiency and toxicity.
28. List some good sources of vitamin C.
29. Refer to highlight 10. Briefly discuss some benefits and drawbacks of vitamin/mineral supplementation. Mention some examples of people who probably should supplement, and discuss briefly how to select supplements.
Supplemental Lectures
I. Cells, energy, and the roles of B vitamins- We haven’t talked about cells using energy much yet. Here’s a little more information, as it relates to the B vitamins.
When cells extract energy from glucose or fatty acids to make ATP (remember, ATP is like a AA battery the cell uses to do work directly), the chemical bonds in those nutrients are carefully split. Splitting the bonds in glucose and fatty acids requires MANY steps, and many enzymes are involved. B-vitamins are structural components of the coenzymes that activate many of these enzymes. So, without B-vitamins, the enzymes that actually extract energy from nutrients don’t work, and the cell cannot get usable energy, even if it has plenty of glucose!
In chapter 7, we will look at the intricate steps involved in extracting energy from glucose and fatty acids; then, I will point out some specific places where B vitamins are involved.
II. Anemia- Anemia is a set of SYMPTOMS associated with a decreased ability of the blood to carry oxygen, for some reason. Anemia itself is not a disease. However, there are many types of anemias, based on why the blood is less able to deliver oxygen. The anemias we discuss are sickle cell, iron-deficiency, and megaloblastic. Megaloblastic is the current chapter’s anemia; it is caused by folate/B12 deficiency. Active folate is required for the proper maturation of red blood cells. Red blood cells are made in bone marrow. Young red blood cells are large, not properly shaped, and not packed with much hemoglobin. They cannot carry much oxygen. Normally, blood cells mature completely within the bone marrow, and will not be released to the blood until they are mature, small, properly shaped, stuffed with hemoglobin and able to carry oxygen. With a lack of folate, many red blood cells never mature, and are released into general circulation in the immature state.
III. Antioxidants- (These are covered in detail in the book in Highlight 11). Reminder: atoms are composed of protons (positive), neutrons (neutral) and electrons (negative). The electrons zip around the protons and neutrons, much like the planets circle around the sun. Anyway, when bonds form, electrons are shared or swapped between specific atoms in specific ways. So, chemical reactions- when chemical bonds change- are all about moving electrons around. Each atom, and each molecule, needs a certain number of electrons to be stable (less reactive); certainly, the molecules of cells will only be functional if they have the right number of electrons. Cell activity often inadvertently produces unstable compounds that are missing an electron.
These unstable compounds are now called free radicals. Free radicals ravage working molecules by stealing electrons from them. This will stabilize the free radical, but turn the pilfered molecule into another free radical; it will steal an electron from someone else, and so on! This kind of domino effect of electron stealing is NOT good for maintaining cell functioning. So, cells keep lots of molecules on hand that can stop this domino effect: antioxidants.
Antioxidants are molecules that can be stable with a couple of different numbers of electrons. So, they can give up an electron or two and still be perfectly stable. Antioxidants will quickly donate electrons to free radicals, stabilizing them, and preventing any other free radicals from being formed.
Figure 10-15 shows vitamin-C as an electron donor. For clarification, electron transfers (when an electron moves from one molecule to another) usually involve H (hydrogen). H atoms have one electron; they happily give it up and exist as H+ (positive because there is now one more proton than electron). So, when vitamin C loses 2 H, the 2 electrons from the Hs go to the free radical, and the H+s just stick around, dissolved in the water of the cell. The 2 electrons vitamin C donates are actually part of H atoms.