55-NUTRITION – Dr. Groseclose

Question 1

What is pellagra? What are the “4 D’s” that characterize it?

Answer 1

Pellagra is a deficiency of niacin; “raw skin.” The 4 Ds are dementia, diarrhea, dermatitis and death.

Question 2

Name the fat-soluble vitamins.

Answer 2

Vitamins A, D, E and K are the fat-soluble vitamins.

Question 3

In addition to solubility, name 3 ways in which the fat-soluble vitamins differ from the water-soluble ones.

Answer 3

Fat-soluble vitamins accumulate in liver and adipose tissue and may be toxic with excessive accumulation. Water-soluble vitamins are not stored in large quantities and are not readily toxic.

Question 4

Name 2 pathways for which thiamin is a cofactor.

Answer 4

Thiamin is a cofactor for the Krebs Cycle (Citric Acid Cycle) and for the Pentose Phosphate pathway.

Question 5

Define:

Answer 5

Beriberi – 1o thiamine (B1) deficiency that is rarely seen today.
Pernicious anemia – vitamin B12 deficiency because no intrinsic factor by stomach lining. (B12 poorly absorbed)
Vitamers – structurally related form of a vitamin.
Scurvy – Vitamin C deficiency; fragile capillaries, swollen and bleeding gums, slow wound healing.
Barlow’s disease – infantile scurvy.
Nyctalopia – nightblindness due to vitamin A deficiency.
Xerophthalmia – dry eyes due to vitamin A deficiency.
Kwashiorkor – protein energy malnutrition(PEM); edema, fatty liver, decreased immune fxn
Marasmus – deficiency of protein and total calories; stunted growth, long-term mental and physical defects.
Complete protein – contain correct ratio of a.a. for normal growth and development.
Glycemic index – blood glucose response from food/response from glucose X 100%

Question 6

What is the biochemical role of niacin? What amino acid is a precursor of niacin in vivo? What vitamins are necessary for the conversion of trp to niacin?

Answer 6

Niacin is the active site of NADP (used for redox reactions). Tryptophan is a precursor of niacin. Pyridoxal and riboflavin are necessary for the conversion.

Question 7

Name 2 enzymes that require a riboflavin-containing cofactor?

Answer 7

Succinic dehydrogenase, monoamine oxidase and glutathione reductase require a riboflavin cofactor.

Question 8

What are the 2 major biochemical roles for pantothenate?

Answer 8

Pantothenate is a structural component of coenzyme A and of acyl carrier protein. It is involved in oxidation of acetate and fatty acids and in the synthesis of fatty acids, steroids, acetyl choline, and porphyrins.

Question 9

For what class of reactions is biotin a cofactor?

Answer 9

Carboxylation reactions

Question 10

What is avidin? In what natural product is it found?

Answer 10

Avidin is a protein in raw egg whites.

Gaston! (beauty and the beast)

Question 11

What is the most common sign of folate deficiency?

Answer 11

Megaloblastic anemia

Question 12

What is the biochemical role of folate?

Answer 12

Folate is a carrier of one-C fragments for the synthesis of purines, thymidine and methionine and for the metabolism of serine and histidine. Folate is the central molecule in one-carbon metabolism.

Question 13

What are the other names for B12? What metal does it contain?

Answer 13

Cobalamin and cyanocobalamin.

Contains Cobalt.

Question 14

Name 3 causes of secondary B12 deficiency?

Answer 14

Failure of the stomach lining to produce intrinsic factor (pernicious anemia)
Gastrectomy
Parasitic infection
NO2 analgesia

Question 15

What are the biological roles of B6?

Answer 15

Vitamin B6 (pyridoxal)
- Carry C groups during transamination and - decarboxylation reactions
Generate niacin from Trp
Metabolism of other AAs
Synthesize porphyrins (5-Ala synthetase)
Breakdown glycogen (glycogen phosphorylase)

Question 16

What is the chemical name of vitamin E?

Answer 16

5,7,8-trimethyltocopherol (alpha-tocopherol)

Question 17

What is the biological role of vitamin K? How is it related to the metabolism of Ca2+?

Answer 17

Vitamin K is needed for coagulation. It is also a cofactor for the gamma carboxylation of glucine groups. It is also a cofactor for the synthesis of Ca2+ binding protein of the kidney, bone and placenta.

Question 18

Explain why “vitamin D” is not really a vitamin. How is 1,25-dihydroxycholecalciferol synthesized in the body?

Answer 18

Vitamin D can be synthesized by the skin with sunlight. Enzymes in the liver and kidney generate 1,25-dihydroxycholecalciferol from vitamin D in response to PTH.

Question 19

What is the normal range of concentration of plasma calcium?

Answer 19

9-10.5mg/100mL

Question 20

How is plasma calcium controlled? (PTH, kidney, vitamin D, etc)

Answer 20

Plasma calcium is controlled by bone remodeling. PTH is able to breakdown bone to raise plasma Ca2+ levels, calcitonin (from the kidney) is able to decrease its secretion from urine and calcitriol is able to absorb Ca2+ from the gut with the help of vitamin D.

Question 21

What other major mineral is controlled with calcium?

Answer 21

Phosphorous

Question 22

What are the biochemical roles of Mg2+?

Answer 22

Used for structural components and wherever ATP participates in a reaction.

Question 23

Name 1 or 2 enzymes for which each of the following minerals is a cofactor: molybdenum, selenium, manganese, zinc.

Answer 23

Molybdenum – xanthine oxidase
Selenium – glutathione peroxidase
Manganese – mitochondrial superoxide dismutase
Zinc – lactate dehydrogenase and carbonic anhydrase

Question 24

With what general biochemical process is chromium associated?

Answer 24

Chromium is associated with the normal action of insulin.

Question 25

What is the biological role of I? What is a goiter?

Answer 25

I is needed for normal growth and development as part of the thyroid hormone. A goiter is an enlarged thyroid gland because of iodine deficiency.

Question 26

What is the biological role of fluorine?

Answer 26

Fluorine strengthens bones and teeth.

Question 27

What are the signs and symptoms of Zn deficiency?

Answer 27

Zinc deficiency shows slow wound healing and diminished smell and taste.

Question 28

Explain the concept of “sparing” with respect to vitamin nutriture.

Answer 28

Absorption vs. mobilization of vitamin. It is possible to have adequate of a nutrient but still not have adequate nutriture.

Question 29

What information do the Harris-Benedict equations yield? What are the variables of those equations?

Answer 29

The equations tell you your RMR (resting metabolic rate) which is your caloric requirement. The variables are gender, age, weight and height.

Question 30

What happens to the protein ingested in excess of that required?

Answer 30

Broken down and stored.

Question 31

What is the equation relating Joules and calories?

Answer 31

1 calorie = 4.2 Joules

Question 32

Name as many roles of dietary fiber as you can.

Answer 32

Dietary fiber provides bulk in the diet and keeps the food bolus hydrated by binding H2O (which keeps the stool soft). They have also been implicated in lowering plasma cholesterol and preventing colon cancer.

Question 33

Why is the recommended lower level of dietary cholesterol at zero? (isn’t cholesterol an essential constituent of membranes?)

Answer 33

Our body has the ability to make cholesterol on its own with out consuming it.

Question 34

What are the recommended proportions of dietary carbohydrate, fat and protein?

Answer 34

Protein 30-40g/day (10-15% of daily calorie content). Fat should be 15-30% of daily calorie content and carbohydrate the rest (typical Western diet = 46% carbohydrates).

Question 35

Why is choline considered in the secretion on dietary fats, though it is not itself a fat?

Answer 35

Choline occurs in the diet in the lipid lecithin (part of egg yolk).

Question 36

What are the effects of dietary fatty acids on plasma cholesterol?

Answer 36

Saturated fatty acids increase plasma cholesterol by much more than a high cholesterol diet alone. Monosaturated fatty acids have no effect on plasma cholesterol, whereas polyunsaturated fatty acids may lower plasma cholesterol.

Question 37

What is the biological role of Vitamin C?

Answer 37

Vitamin C (ascorbate) - Proper synthesis of collagen - C-terminal amidation of neuropeptides - Fxn of dopamine b hydroxylase - Reducing agent - Antioxidant in vivo (sparing effect on vitamins A and E)

Question 38

Name 4 processes in which vitamin A plays a role. What is a major source of this vitamin synthesized by plants?

Answer 38

1. Vision 2. differentiation of epithelial cells 3. maturation of cartilage into bone 4. proper maturation and maintenance of the reproductive system. Vitamin comes from green and yellow vegetables like carrots (carotene), liver and dairy products.

Question 39

What is the role of vitamin E?

Answer 39

Lipid-soluble antioxidant