Fat-Soluble Vitamins

Question 1

What are the 3 vitamins (active forms) of vitamin A

Answer 1

retinal, retinol, retinoic acid

Question 2

What cleaves beta carotene into retinol and retinal

Answer 2

the brush border enzyme dioxygenase

Question 3

Why is only 1 mg of Vit A derived from 6mg of beta carotene

Answer 3

Dioxygenase doesn’t always cleave beta carotene perfectly, so discards the short strand and trims the long one

Question 4

is beta carotene or Vit A stored in the body

Answer 4

Beta carotene is stored in fat (making it yellow), Vit A is predominately stored in the ITO cells of the liver

Question 5

What is the storage form of Vit A

Answer 5

retinol esters with fatty acids

Question 6

What is the role of retinoic acid

Answer 6

Acts like a lipid soluble hormone

Question 7

How are isoprenes formed

Answer 7

via the mevalonic acid pathway

Question 8

How does Vit A get to cells

Answer 8

via chylomicrons

Question 9

Where is 11-cis retinal used

Answer 9

it’s a component of rhodopsin

Question 10

What is transthyretin

Answer 10

protein that carries thyroid hormones and also binds to retinol-RBP complex

Question 11

Why is it significant that transthyretin bind to the retinol-RBP complex

Answer 11

Because it would be filtered out of the blood by the kidney but transthyretin prevents this

Question 12

What happens to a basal cell if it receives copious Vit A

Answer 12

It grows up to be cuboidal, columnar, or goblet cell

Question 13

What happens to a basal cell if it receives little Vit A

Answer 13

It grows up to be squamous (keratinized)

Question 14

How many genes are regulated by Vit A

Answer 14

possibly 500 different ones

Question 15

How does Vit A affect genes

Answer 15

It binds to a RAR: retinoic acid receptor

Question 16

What is a homodimeric RAR

Answer 16

2 receptors both bind vit A and then act as a unit of DNA

Question 17

What is a heterodimeric RAR

Answer 17

One half binds Vit A, the other binds Thyroid hormone, Vit D, prostaglandin, etc

Question 18

Where does cholecalciferol come from

Answer 18

formed from the action of UV light (297nm) on 7-dehydrocholesterol

Question 19

What layers of the skin make cholecalciferol

Answer 19

stratum spinosum and basal layers

Question 20

How do the liver and kidney hydroxylate Vit D precursors

Answer 20

They use CYP27A and CYP27B, respectively (phase 1 metabolism)

Question 21

How is Vit D absorbed from the GI tract

Answer 21

It is absorbed like a fat, via bile salt emulsification etc

Question 22

What is Vit D synthesis in the skin contingent upon

Answer 22

Temperature and melanin

Question 23

What’s the half life of cholecalciferol (Vit D from skin)

Answer 23

36-72 hours

Question 24

What’s the half life of 25-hydroxycholecalciferol (Vit D from liver)

Answer 24

15 days

Question 25

What's the half life of 1,25-dihydroxycholecalciferol (Vit D from kidneys)

Answer 25

4-15 hours

Question 26

How many genes are targeted by Vit D

Answer 26

200-3,000

Question 27

how many receptor types are there for Vit D

Answer 27

35

Question 28

how many tissues make Vit D

Answer 28

17

Question 29

What is the role of Vit E in the body`

Answer 29

Prevents free radical damage in polyunsaturated fats

Question 30

Where can Vit E be found

Answer 30

It is a membrane associated vitamin

Question 31

How is Vit E metabolized

Answer 31

It is not metabolized

Question 32

What is the scientific name of Vit E

Answer 32

Vit E is a mix of Tocopherols and tocotrienols; alpha tocopherol is best

Question 33

What is the scientific name of Vit K

Answer 33

Menaquinone = K2, phylloquinone = K1

Question 34

What's the structural difference between K1 and K2

Answer 34

K1 isoprene tail is saturated, K2 is unsaturated

Question 35

How are subsets of Vit K2 named

Answer 35

With MK- and a number to designate the number of isoprene units in the tail

Question 36

Which Vit K2 subsets are favored by the body

Answer 36

MK-4, MK-7

Question 37

What is our main source of Vit K

Answer 37

Dietary; it is absorbed as fats are

Question 38

What is the head unit of Vit K called

Answer 38

2-methyl-1,4-napthoquinone

Question 39

What is Vit K's traditionally understood role in the body

Answer 39

It is a cofactor in the carboxylation of clotting factors: proteins C, S, Z, and factors II, VII, IX, X

Question 40

Why are infants at increased risk for Vit K deficiency

Answer 40

They have low vitamin K stores at birth, vitamin K passes the placenta poorly, the levels of vitamin K in breast milk are low and the gut flora has not yet been developed

Question 41

How does Vit K affect Calcium

Answer 41

It utilizes and regulates calcium action; uses osteocalcin and matrix GLA protein to do this

Question 42

What is osteocalcin

Answer 42

protein in bone matrix involved in capturing and depositing Ca2+ in bone

Question 43

What is matrix GLA protein

Answer 43

Protein in blood vessels that inhibits calcification of soft tissue