Fat Soluble Vitamins

Question 1

What are the fat soluble vitamins?

Answer 1

A,D,E,K

Question 2

What do fat soluble vitamins need for absorption?

Answer 2

Bile and fats (emulsifiers)

Question 3

What is an emulsifier?

Answer 3

Consists of a water loving hydrophilic head and an oil loving hydrophobic tail. The hydrophilic head is directed to the aqueous phase while the hydrophobic tail is directed to oil phase.

Question 4

Where are excess vitamins stored?

Answer 4

Liver and adipose tissue

Question 5

Digestion and absorption of fat soluble vitamins

Answer 5

1) Bound to proteins as we eat them.
2) Once in stomach, they are degraded into small peptides releasing vitamins.
3) Form micelles with bile salts allowing them to passively transport into intestinal enterocytes.
4) They are packaged into chylomicrons and released into lymphatic system.
5) Travel up the thoracic duct and enter left subclavian vein to enter circulation.

Question 6

How do we obtain Vitamin A?

Answer 6

Retinyl esters from animal food and beta carotene from plant food. Retinal esters are converted into Retinol while beta carotene is converted into Retinal. Retinal is converted into Retinoic Acid

Question 7

What is retinol important for?

Answer 7

Supports reproduction.

Question 8

What is Retinal important for?

Answer 8

Participates in vision.

Question 9

What is retinoic acid important for?

Answer 9

regulates growth

Question 10

Is the conversion of Retinol into Retinal reversible?

Answer 10

Yes they can interconvert.

Question 11

Is the conversion of Retinal into Retinoic Acid reversible?

Answer 11

No.

Question 12

Liver is rich in Vitamin A (remember polar bear story). What form of vitamin A?

Answer 12

Retinyl esters

Question 13

What vegetables are best for vitamin A and in what form?

Answer 13

Sweet potatoes and carrots. Vitamin A in form of Beta Carotene.

Question 14

Biochemically, what is the difference between retinol, retinal, retinoic acid, and beta-carotene?

Answer 14

Retinol has a hydroxyl group, Retinal has an aldehyde, retinoic acid has a carboxyl group, and Beta carotene is a dimer of two retinal molecules.

Question 15

What is the form of vitamin A that is circulating within chylomicrons in the plasma?

Answer 15

Retinol Ester

Question 16

Where is retinol stored?

Answer 16

Retinol is stored in the stelatte cells.

Question 17

Functions of Vitamin A

Answer 17

Vision
Maintenance of cornea, epithelial cells, mucous membranes, skin
Bone and tooth growth.
Reproduction
Immunity

Question 18

Function of beta-carotene

Answer 18

Antioxidant

Question 19

What happens to the epithelia in absence of vitamin A?

Answer 19

Goblet cells cannot function properly leading to flattened, abnormal epithelial cells with very little mucous.

Question 20

What is the pharmacological use of retinoic acid?

Answer 20

Treatment of acute promyelocytic anemia

Question 21

All Trans Retinoic acid (Retin-A) is also called? What is its use?

Answer 21

Tretionin, it is used as a topical treatment for acne, aging, dark pigments

Question 22

Pharmacological use of 12-cis retinoic acid?

Answer 22

Isotretionin, (Accutane) and is used as oral treatment for cystic acne. Also it is a teratogen so it requires use of effective contraceptives.

Question 23

Why is vitamin D important in vision?

Answer 23

Cells of retina, rods, contain pigment molecules called rhodopsin. It is composed of a protein called opsin bonded to a molecule of retinal.

Question 24

Mechanism of retinal in eye

Answer 24

As light interacts with rhodopsin, retinal changes from cis to trans and it is released from opsin. The change allows opsin to initiate signal transduction cascade to nerve cells that communicate with the brain’s visual center. THIS IS IMPORTANT FOR NIGHT VISION.

Question 25

What is 1' deficiency of hypovitaminosis A vs. 2' deficiency?

Answer 25

Primary deficiency is inadequate intake. Secondly deficiency is poor absorption of fats and can result from cystic fibrosis, crown's disease, liver disease, excessive alcohol intake.

Question 26

Symptoms of hypovitaminosis A?

Answer 26

``` Night blindness Blindness (xerophthalmia) Corneal drying (xerosis) triangular gray spots on eye (bitot spots) Softening of the cornea (keratomalacia) Dry skin due to hyperkeratosis impaired immunity ```

Question 27

What happens to babies if moms use lots of accutane treatment during pregnancy?

Answer 27

Birth defects such as cranofacial malformation and malformation of CNS, Thymus, and heart

Question 28

What is the other name of vitamin D?

Answer 28

Calciferol

Question 29

What are good food sources of vitamin D?

Answer 29

Fish, fortified milk and mushrooms

Question 30

Factors that contribute to deficiency?

Answer 30

Dark skin, no sun exposure, use of non fortified milk, vegan diet

Question 31

What does vitamin D deficiency cause in infants and adults

Answer 31

Rickets in infants and osteomalacia in adults

Question 32

How else can osteomalacia develop?

Answer 32

Long term anticonvulsants such as phenobarbital and phenytoin can cause increased breakdown of vitamin D in liver. And also in chronic kidney disease.

Question 33

How does Vitamin D toxicity occur?

Answer 33

Occurs with supplementation and causes calcification of soft tissue.

Question 34

What is the other name for vitamin E?

Answer 34

Tocopherol

Question 35

Which molecule has vitamin E activity?

Answer 35

d-isomer of alpha tocopherol

Question 36

How can d-isomer of alpha tocopherol be destroyed?

Answer 36

Oxygen or frying

Question 37

What are good sources of vitamin E?

Answer 37

nuts and oil

Question 38

Functions of vitamin E

Answer 38

Most effective lipid soluble antioxidant. Prevents platelet aggregation and monocyte adhesion. Assists in maintenance of fertility.

Question 39

What does vitamin E depend on for activity

Answer 39

It depends on vitamin C

Question 40

Vitamin E deficiency

Answer 40

Rare but can happen in premature babies. Causes erythrocyte hemolysis causing hemolytic anemia. We give premature babies vitamin E.

Question 41

What is the animal form of vitamin K

Answer 41

menaquinone, made by gut bacteria and can be obtained from fish oil and meats.

Question 42

What is the plant form of vitamin K

Answer 42

phylloquinone, can be obtained from green leafy vegetables, broccoli, peas and green beans.

Question 43

Function of vitamin K

Answer 43

Required cofactor for post translational modification of glutamate to gamma-carboxyglutamate (GIa). Plays role in coagulation

Question 44

What enzyme catalyzes glutamate to GIa reaction?

Answer 44

Gamma-glutamyl carboxylase

Question 45

What can cause deficiency of vitamin K?

Answer 45

Use of antibiotics or malabsorption

Question 46

Why do newborns have vitamin K deficiency and what can be done?

Answer 46

Due to lack of gut bacteria and we can give bolus of vitamin K injections shortly after birth.

Question 47

What can cause toxicity of vitamin K?

Answer 47

Patients taking warfarin.