Fat Soluble Vitamins (A, D, E, and K)

Question 1

Active forms of Vitamin A

Answer 1

• 11-cis retinal (for vision)

- Retinoic acid (for all other functions)

Question 2

Two major classes of Vitamin A and examples of each

Answer 2

Provitamin A (carotenoids) - converted after ingestion
- Ex: tomatoes, mangoes, papayas, oranges, carrots

Preformed Vitamin A (retinol)
- Ex: eggs and milk

Question 3

Carotenoids with Provitamin A activity

Answer 3

• B-carotene (tomatoes, mangoes, papayas)
• B-cryptoxanthin (oranges, papayas)
• alpha and beta-carotene (carrots)

Question 4

How is vitamin A absorbed into the intestine?

Answer 4

Absorbed with fat

- absorbed as RE (retinol ester) or Beta-carotene

Question 5

How is vitamin A transported to the liver and target organs?

Answer 5

It’s transported to other target organs in lipoprotein particles
- Retinoic acid can travel bound to albumin

Question 6

Functions of Vitamin A

Answer 6

Formation of rhodopsin (needed in: vision, control of embryogenesis, cell division, cell differentiation, control of gene expression for many genes

• Other vitamin A genes control neuronal regulation, enzyme function, receptor function, growth factors, and cytokine production

Question 7

Problems in getting Vitamin D from diet

Answer 7

• only found in a few foods naturally (salmon, mushrooms, egg yolk)
• fortify it in milk and dairy
• get it from sunlight (not much in diet)

Question 8

Functions of Vitamin D

Answer 8

• increases calcium absorption in intestine
• increase renal reabsorption of calcium
• increase gene expression of a number of genes
• helps regulate blood calcium
• involved with regulation of cell differentiation and cell division

Question 9

Symptoms of Vitamin D deficiency

Answer 9

soft bones, pain and weakness in the muscles, and osteomalcia (rickets)

Question 10

Organ responsible for activating Vitamin D as needed

Answer 10

skin, intestines, and prostate

Question 11

Function of Vitamin E

Answer 11

• lipid soluble antioxidant that prevents fatty acid oxidation (prevents damage to tissues by preventing lipid oxidation)

Question 12

Best dietary sources of Vitamin E

Answer 12

Dietary plant oils (vegetable oils, walnut oils, canola oils)

Question 13

Which stereoisomers of Vitamin E are active?

Answer 13

R and S

Question 14

What is tocopheral transfer protein (TTP)?

Answer 14

• the main Vitamin E transport protein

- shows Vitamin E is involved with neurological functions as well as a lipid antioxidant

Question 15

What happens during TTP deficiency?

Answer 15

• neurological problems
• unsteady gait
• inability to walk straight and use limbs

Question 16

Function of Vitamin K

Answer 16

• primary function: lipid antioxidant that protects cell membranes
• Post-translational modification of proteins involved with blood clotting and bone matrix formation

Question 17

Why is recycling of Vitamin K in the body necessary?

Answer 17

• We don’t get much Vitamin K in our diet but our needs are fairly high
• we need to reuse what we have