Block 2: ADEK

Question 1

What are the components of vitamin A?

Answer 1

beta-ionone rign with an isoprenoid chain

Question 2

What are the forms of Vitamin A?

Answer 2

1. Retinol (alcohol) - vision
2. Retinal (aldehyde) - vision
3. Retinoic acid (acid) - growth and differentiation

Question 3

What is the precursor or Vit A? And its precursor?

Answer 3

Gamma carotene -> beta-carotene -> vit A

Question 4

Describe the conversion of b-carotene to retinol?

Answer 4

B-caroten is cleaved by 15, 15-carotenoid dioxygenase to form retinal (theoretically forms 2 retinal however doesn’t happen in vivo)

Question 5

How much of b-carotene is lost in the intestine without being converted to retinol?

Answer 5

> 30%

Question 6

Conversion of food source dietary vitamin A (retinol)

Answer 6

Dietary or supplementary 1 μg → 1 μg retinol
Supplementary β-carotene (oily) 2 μg → 1 μg retinol
Dietary β- carotene (food) 12 μg → 1 μg retinol
Dietary ⍺-carotene (food) 24 μg → 1 μg retinol

Question 7

How is Vit A absorbed into the body?

Answer 7

Chylomicron remnant deliver retinyl esters and part of carotenoids to liver -> hydrolyzed to retinol by binding to CRPB and transported to tissues (stellate cells)

Question 8

What are the functions of VitA?

Answer 8

Retinol and retinal: Vision
Retinoic acid: Embroyonic devo and repro, bone metabolism, hematopoiesis (cell growth and proliferation)

Question 9

How does vit a contribute to vision?

Answer 9

1. When light hits retinal portion of rhodopsin it shapes shape (isomerization back to trans form)
2. All trans retinal formed is converted to 11-cis retinal

Question 10

What are the gene transcription receptors of Vit A? MOA?

Answer 10

1. RAR
2. RXR

• Retinoic acid binds to receptors inducing dimerization where confo change causes co-receptors to dissociate from receptor
• Receptors can bind to responce elements on DNA and upregulate or down the expression of target gene

Question 11

Sources of Vit A?

Answer 11

Liver and carrots

Question 12

Def of Vit A?

Answer 12

1. Growth retardation
2. Infections
3. Keritinization
4. Xeropthalamia (Bitots spot)

Question 13

Toxicity of Vit A?

Answer 13

10x RDA -> hypervitaminosis A

Question 14

What are the forms of Vit D?

Answer 14

Vit D2 (ergocalciferol)
Vit D3 (cholecalciferol)

Question 15

Describe the synthesis cholecalciferol?

Answer 15

Irradiation of 7-dehydrocholesterol (intermediate in cholesterol synthesis) from sunlight to previtamin D3 -> 2-3 days to D3 -> transported through skin to blood by DBP

Question 16

How is 7-dehydrocholesterol synthesized?

Answer 16

Sebaceous glands of the skin secreted onto the surface and reabsorbed into the epidermis

Question 17

Describe the activation of Vit D3?

Answer 17

In the liver, 24,25-hydroxyl form is the inactive form that gets converted to the 1,25 form which is active

Question 18

What is the primary function of calcitriol?

Answer 18

Increased absorption of Ca2+ and P:
1. Carried into the nucleus of the enterocyte where it binds to receptor proteins and acts as a steroid hormone

Question 19

Describe the activity of calcitriol?

Answer 19

1. Stimulates and synthesizes of new mRNA
2. mRNA is translated to calbindin (protein)
3. Calbindin is a calcium binding protein in the intestinal mucosa required for Ca2+ transport across cell membranes

Question 20

What are the signs of Vitamin D def?

Answer 20

Due to inadequate intake or sunlight exposure:
1. Rickets in children
2. Osteomalacia in adults
3. Osteoporosis

Increase high BP and CV risk

Question 21

What are signs of vit D tox?

Answer 21

Hypervitaminosis D from OD
* excessive exposure to sun doesn’t cause tox by overproduction of endogenous cholecalciferol
* Hypercalcemia

Question 22

What are sx of Vit D poisoning

Answer 22

1. Dehydration
2. V
3. Anorexia
4. Irritability
5. C
6. Fatigue

Question 23

What is the receptor of Vit D?

Answer 23

Vitamin D receptor (VDR), a type 1 nuclear receptor and DNA transcription factor

Question 24

What are the classes of Vit E?

Answer 24

1. Tocopherols (saturated side chains)
2. Tocotrienols (unsaturated side chains)

Question 25

What is the common structures of Vit E?

Answer 25

Chromanol ring + a-Tocopherol

Question 26

What Vit E for has the highest F?

Answer 26

a-tocopherol

Question 27

What are the sources of Vit E?

Answer 27

a-tocopherol

1 a-tocopherol equivalent (TE) = 1 mg of a-tocopherol

Question 28

What is the primary function of Vit E?

Answer 28

Maintenance of membrane integrity in body cells by preventing oxidative destruction (perioxidation) of FA contained in phospholipids of the cellular membranes

Question 29

What tissues are susceptible to oxidation?

Answer 29

Lungs, Brain, RBC

Question 30

How is vitamin E regenated?

Answer 30

The reduction of vitamin E back to its antioxidant form requires vitamin C, reduced glutathionine (GSH), and NADPH

Question 31

What is the synthetic form of Vit K? Natural?

Answer 31

Menadione (K3)

Phylloquinone (K1) - Plants
Menaquinone (K2) - Bacteria and animal

Question 32

What is the primary function of Vitamin K?

Answer 32

Required as an enzymatic cofacotr involved in the carboxylation of glutamate residues on the N-terminal portion of important precursor proteins; forms y-carboxyglutamate

Question 33

Sources of Vitamin K?

Answer 33

Dark green leafy veggies

Question 34

What patient population is at risk for vit K def?

Answer 34

Neborn infant and people who have been injured or treated chronically with antibiotics (destruction of GTI bacteria that synthesize vit)