Exam 1

Question 1

Which of the fat-soluble vitamins is consumed in the form of phylloquinone from plant foods?​

Answer 1

vitamin K

Question 2

How does alpha-tocopherol differ from beta-tocopherol?​

Answer 2

​number and location of methyl groups

Question 3

Subclinical vitamin K deficiency may be associated with diminished bone mineral density and increased fracture rates.​

Answer 3

True

Question 4

Risk of vitamin K deficiency is greatest in ____.

Answer 4

Newborns

Question 5

Which vitamin has as its primary function the maintenance of calcium homeostasis?​

Answer 5

vitamin D

Question 6

Retinol must be reesterified to be carried in the chylomicron.

Answer 6

True

Question 7

In what cells will you find most of the retinol and vitamin A stored?​

Answer 7

stellate

Question 8

How will retinol, once secreted from the liver, be found in the blood?​

Answer 8

​attached to RBP and transthyretin

Question 9

Structurally, vitamin D is derived from ____.​

Answer 9

​a steroid

Question 10

Many anticoagulants work by inhibiting the regeneration of active vitamin K (i.e., dihydrovitamin KH2) during the vitamin K cycle.​

Answer 10

True

Question 11

Rhodopsin is simply the opsin protein after it has been activated by 11-cis-retinal.​

Answer 11

True

Question 12

The majority of vitamin A is stored in the liver, while carotenoids are stored mainly in the ____ tissue.​

Answer 12

adipose

Question 13

Calcitroic acid and vitamin D metabolites are excreted primarily through ____.​

Answer 13

feces

Question 14

Immediately following a balanced meal that contained vitamin E (such as fortified milk), where would you most likely find most of the vitamin E in the body?​

Answer 14

​in chylomicrons in the lymphatic vessels and general circulation

Question 15

Vitamin A enhances vitamin K absorption and increases the plasma concentration of vitamin E.​

Answer 15

False -
​Vitamin A has the exact opposite effect. It will interfere with vitamin K absorption and decrease plasma vitamin E concentrations.

Question 16

The action of vitamin K in the posttranslational synthesis of blood clotting factors occurs in the____.​

Answer 16

liver

Question 17

Which antioxidant is most effective in rapidly eliminating hydroxyl radicals prior to initiation of oxidative damage?​

Answer 17

​vitamin C

Question 18

Which substance accounts for almost half of the antioxidant capacity of human plasma?​

Answer 18

​uric acid

Question 19

nuclear receptors and their specific ligands for vitamin A

Answer 19

All-trans retinoic acid binds to retinoic acid receptors (RAR)

All 9-cis retinoic acid binds to retinoid X receptors (RXR)

Question 20

nuclear receptors and their specific ligands for vitamin D

Answer 20

VDR & Calcitriol

Question 21

Define RAE and why it is used for vitamin A DRIs.

Answer 21

RAE = mg retinol activity equivalents.
Used to account for the differences in retinol generated in the body from pro-vitamin forms versus preformed vitamin A.

Question 22

27. How does the use of anticoagulants interact with vitamin E?

Answer 22

It can increase the risk of bleeding due to its inhibition/effects on vitamin K metabolism (aka synergistically)

Question 23

Define the term free radical

Answer 23

Free Radical - an atom, molecule, or molecular fragment that is capable of free existence (although in most cases for very short time periods) and has one or more unpaired electrons

Question 24

antioxidant

Answer 24

substances that may protect your cells against free radicals

Question 25

How does vitamin E and vitamin K metabolism interact?

Answer 25

Vitamin E inhibits vitamin K metabolism by converting phylloquinone to menaquinone

Question 26

K1 (Phylloquinones) dietary sources and function(s)

Answer 26

tend to come from leafy green vegetables. Functions in blood clotting

Question 27

K2 (menaquinones) dietary sources and function(s)

Answer 27

Tend to come from more animal sources and fermented foods. Calcium metabolism. Bone Health.
Prevents calcification in vessels. Shown to play a role in improving outcomes for osteoporosis, atherosclerosis, cancer and inflammatory diseases.

Question 28

Describe the role of vitamin K in blood clotting.

Answer 28

Vitamin K1 (phylloquinone) acts as cofactor for enzymes involved in blood clotting.

Question 29

Describe the role of vitamin K in cardiovascular health.

Answer 29

Vitamin K dependant proteins (i.e. MGP - matrix gla protein) are in vascular tissues. They inhibit calcification in vascular and other tissues.

Question 30

Explain why the DRI varies by age or group for vitamin D.

Answer 30

Age related differences in growth and development: Infants, children and adolescents are in a rapid growth state and need larger vales of vitamin D.
Infants and older adults may have less sensitivity to UVB radiation.
Physical activity levels: older adults are usually unable to be as physically active and therefore get less exposure to UVB.
Pregnancy and lactation: pregnant and lactating women need a higher intake of vitamin D to support fetal growth.

Question 31

Biologically active Vitamin A

Answer 31

Retinol is the biologically active form, it plays a critical role in vision, immune function, skin health, and various other physiological processes.

Question 32

Biologically active vitamin D

Answer 32

25-OH D or Calcidiol (after hydroxylation in the liver by 25-hydroxylase)

Question 33

Biologically active vitamin E

Answer 33

Alpha-Tocopherol is the biologically active form. Plays a huge role as an antioxidant (protecting cell membranes from oxidative damage).

Question 34

Biologically active vitamin K

Answer 34

There are 2 primary forms of vitamin K, Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinones). Phylloquinone is the most biologically active form and responsible for blood clotting…..

Question 35

Describe the role of 1-hydroxylase, 24-hydroxylase, and 25-hydroxylase in vitamin D metabolism.

Answer 35

(A) 25-hydroxylase metabolizes Cholecalciferol in the liver to 25-OH-D
(B) 1 hydroxylase synthesizes calcitriol in Kidney from 25-OH-D (activation)
(C) 24-hydroxylase - “deactivate”s vit D when no longer needed

Question 36

Explain how vitamin D metabolism might be affected if there is liver and/or kidney failure.

Answer 36

Vitamin D is activated by two hydroxylation reactions -
First in the liver (D3 aka Cholecalciferol metabolized to 25-OH D)
In the Kidneys [25-OH D is converted to 1,25-(OH)2D (calcitriol) ]

Question 37

Describe the vitamin D synthesis pathway in humans

Answer 37

UVB exposure activates 7-dehydrocholesterol in the skin –> absorbed photons —> converted to previtamin D3 (pre cholecalciferol) —> Thermal isomerization—> converted to Vitamin D3 (cholecalciferol, the biologically active form) . Diffuses from skin to blood.

Question 38

what factors can affect vitamin D synthesis

Answer 38

time of day, season, latitude, altitude, cloud cover, air pollution, skin pigmentation, sun- screen use, and age.
-During the winter, the morning and late-afternoon hours, and North and South of latitudes of about 40 degrees, there is an increase in the zenith angle of the sun (diminishes vit D production in the skin)
-Older adults may produce up to 75% less vitamin D3 in the skin than younger adults (diminished 7-dehydrocholesterol content in the skin)

Question 39

Describe the metabolism of vitamin A after it enters the liver.

Answer 39

When needed, the esterified retinol is hydrolyzed (by retinyl ester hydrolase, REH) and converted back to retinol and attaches to a retinol binding protein (RBP) & transthyretin for transport to target tissues.
When not needed, The liver stores the Vitamin A (Retinol) as esterified retinol (by LRAT) in stellate cells
Some retinol may be conjugated to glucuronic acid to form retinoid/retinoyl b-glucuronide
*hepatic retinoyl b-glucuronide is usually excreted in the bile

Question 40

role of ARAT

Answer 40

acyl-CoA retinol acyl transferase (ARAT) = 2nd Minor pathway for reesterification
*fatty acids used esterify retinol are those present in the enterocyte from dietary fat consumption (diff from LRAT)
Occurs in mucosal cells

Question 41

role of LRAT

Answer 41

lecithin retinol acyl transferase (LRAT) esterifies CRBPII-bound retinol to retinyl palmitate (mostly) & others.
* Thought to be the main enzyme responsible for esterification in the small intestine, liver, pigment epithelium of the retina, and likely other tissues.

Question 42

vitamin D Dietary Sources

Answer 42

Fatty fish (e.g., salmon, mackerel)
Fortified foods (e.g., fortified dairy products, cereals)
Sunlight exposure (for vitamin D synthesis)

Question 43

vitamin A dietary sources

Answer 43

Retinol: Liver, fatty fish, dairy products
Provitamin A carotenoids (beta-carotene, alpha-carotene, beta-cryptoxanthin): Orange and green vegetables (e.g., carrots, sweet potatoes, spinach)

Question 44

vitamin E dietary sources

Answer 44

Vegetable oils (e.g., sunflower, safflower, wheat germ oil)
Nuts and seeds (e.g., almonds, hazelnuts)
Green leafy vegetables

Question 45

vitamin K dietary sources

Answer 45

Vitamin K1: Leafy green vegetables (e.g., kale, spinach, broccoli)
Vitamin K2: Meat, dairy, fermented foods (e.g., natto, cheese)