Exam 2

Question 1

Which statement is true for intrinsic factor?

Answer 1

Binds cubulin.

Question 2

Which reaction requires B12?

Answer 2

Homocysteine to methionone

Question 3

Which reaction requires niacin?

Answer 3

Quinon -> hydroquinon

Question 4

What is the final destination for retinoic acid?

Answer 4

Nucleus

Question 5

What is the general role of folate?

Answer 5

Methyl transfer

Question 6

What is the daily recommended intake for folate (in ug) from food sources? from supplements?

Answer 6

DRE = 400 mcg/d
Food sources = 400 mcg/d
Supplements = 200 mcg/d

Question 7

State (1) an excellent food source of vitamin E and (2) how to best optimize the absorption of Vitamin E from this food source?

Answer 7

Raw almonds
Anything containing Vit E should be eaten with >10g of fat and foods containing fiber should be avoided during the same meal.

Question 8

How is vitamin A status/metabolism impacted by dietary intakes of three other nutrients?

Answer 8

Vitamin E - interferes with beta carotene converting to retinal
Iron helps convert beta carotene to retinal
Niacin converts RAL-> RA or ROL RAL

Question 9

Describe Vitamin K turnover and storage?

Answer 9

Vitamin K is stored in the cellular membrane of various tissue including the liver, heart, lungs, kidney, etc.
Put on test: Vitamin K has to be reduced in order to perform carboxylation of glutamic acids. After carboxylation, its recycled back to its oxidized form. 60% is metabolized and excreted (urine 20%/bile 40%) daily.
From notes: Vitamin K is not well stored and has a high turnover. 60% of dietary vitamin K is metabolized and excreted daily. 40-60% is excreted as bile and 20% is excreted in the urine. It is excreted in its oxidized form, 5C-aglycone.

Question 10

What supplemental form of Vit E would provide the most “bang for the buck”? why?

Answer 10

RRR - α- tocopherol : active form of vitamin E (R series)
All-rac-α-tocopherol would only provide half as much active vitamin E because it contains both the R and S series. S-series is not active.

Question 11

You had liver and onion for dinner. Discuss the retinoid present in liver and how it is processed by the body and used to promote vision in dim light?

Answer 11

retinoid present in liver: When reinol in the liver, it could convert to retinyl ester for storage
promote vision in dim light: Retinol can convert to retinal using niacin. Cis retinal plus opsion creates rhodopsin. When the light hit retina, rhodopsin break, cis retinal convert to tran retinal and that’s how they send signal to the brain.
The retinoid found in the liver consumed is retinyl ester bound to protein. Pepsin and other proteases cleave the bond with the protein. Hydrolases, esterases and lipases cleave the long tail on RE leaving free retinol. Fat globules begin to form which stimulates the release of bile. Bile emulsifies the fat globules that are then incorporated into micelles which are passively diffused across the brush border into the enterocyte. Inside the cell, RE reforms and is incorporated into a chylomicron which allows it to exit the cell and enter the lymph-> thoracic duct -> blood-> liver. When ready for use, the liver convert RE -> ROL and sends it out to the tissue in need on the RBP (retinol binding protein). Once it reaches the cell its converted to RAL via the NADPH dependent enzyme retinol dehydrogenase.. Retinal is a cofactor of Rhodopsin, a pigment found in the rods of the eye which allows for vision in low levels of light.

Question 12

Why are B12 supplement and not food sources advised for adults > 51 years? Discuss two concerns when choosing a B12 supplement?

Answer 12

Because HCl acid is necessary for the digestion of B12 from food sources. The elderly are more likely to suffer from achlorhydria which affects their B12 status from foods. B12 supplements do not need to be digested and are absorbed at 100% making them a better source of B12 for the elderly.
Other nutrients, when combined in a supplement, can affect the integrity of B12 and therefore is best taken alone. The label should also have the USP seal to ensure proper dosage and dissolvability.

Question 13

List the 3 forms of Vitamin K and their sources? which forms of vitamin K is the AI based on and why?

Answer 13

K1- phyllaquinone -> plants
K2 - meanquinone -> gut bacteria
K3 - menadione ->supplements
The AI is based on K1. There is not enough scientific research done on Vitamin K. Researchers also have not collected enough statics for it. Therefore, it is now just an estimate rather than a concreted fact.

Question 14

Explain the digestion/absorption process for Vit E. Describe the path Vit E takes to reach(1) adipose tissue and (2) extrahepatic tissue.

Answer 14

RRR (free form, no digestion required) is consumed -> stomach -> bile is released and emulsifies the fat. A micelle is formed and takes the fat soluble vitamin into the cell. From the cell, a chylomicron is formed that can then enter the lymph, travel to the thoracic duct and from there enters the blood. Once in the blood it will travel to the adipose tissue or the liver. If the liver wants to send it out, it uses α-TTP->VLDL->LDL-> HDL

Question 15

Describe the anemias associated with folate deficiency and Vit E deficiency. Clearly state the roles each vitamin plays in maintaining healthy red blood cells

Answer 15

Folate - megaloblastic macrocytic anemia - The absence of folate does not allow the blood cell to undergo DNA synthesis which leads to large immature blood cells to form. It can cause individuals to feel tired, weak or short of breath.
Vit E - hemolytic anemia - blood cells are lysing because vit E is not present in order to protect against the integrity of the cell. Cell wall lysis.

Question 16

Describe how each of the following Vitamins are transported in systemic blood to target tissues. For each vitamin, state a situation that reduces transport efficiency aside from a vitamin deficiency

Answer 16

Retinol - from the enterocyte -> chylomicron picks it up -> goes to lymph -> thoracic duct -> bloodstream -> liver (stored as RE) or tissues. From liver, RBP takes ROL to cells. In beta carotene form, it uses VLDL->LDL. Comes back to liver using HDL. Any malabsorption disorders would affect transportation (no gallbladder, resectioning); high fiber diets (interferes w/ micelle formation); and low fat intake would also interfere or decrease this process.
B12 - TCII transports B12 in the blood to the cell where is it is engulfed. A TCII polymorphism would hinder this process.

Question 17

Discuss the general function of Vitamin K and describe with detail two physiological processes dependent on Vitamin K

Answer 17

Vitamin K carboxylates glutamic acid residues on proteins which allows them to carry out their function
Blood clotting - vitamin K carboxylates the clotting proteins. If injured, cells release Ca+ that will then attract the clotting factor and allow a clot to form.
Osteocalcin - Vit K carboxylates osteocalcin which attracts Ca+ and forms the structure of our bones

Question 18

Discuss the form of folate in the following foods and rank order these foods using the calculated folate biocailability

Answer 18

Supplement (400ug), black-eye peas (534 ug/c), cheerios (400 ug/c)
#1 supplement: @ 100% =  400 mcg; contains folic acid which is absorbed at 100% -> most effective
#2 The cheerios: @ 85% would provide 340 mcg; fortified forms are absorbed at 85%
#3 black-eye peas: @ 50% = 267 mcg of folate; natural forms @ 50%

Question 19

Which of the 5 vitamins have UL? state the UL and the basis of the UL

Answer 19

Folate - 1000 mcg - masks a B12 deficiency, potential harm from unmetabolized folic acid
Vitamin A - 3000 mcg - hypervitaminosis -> liver cirrhosis conditions, carcinogenic byproducts
Vitamin E - 1000 mcg - all forms - risk of bleeding