Vitamin K

Question 1

What are the two natural forms of vitamin K?

Answer 1

1. K1 (Phylloquinone) - plant sources
2. K2 (Menaquinone) - animal sources and synthesized by GI bacteria

Question 2

What is the plant-based source of vitamin K?

Answer 2

Phylloquinone, K1 (MAJORITY)

Question 3

What is the animal-based source of vitamin K?

Answer 3

Menaquinones, K2

Question 4

What is the average adult intake of phylloquinones a day?

Answer 4

~70 to 80 micrograms

Question 5

(TRUE/FALSE)

Intakes of vitamin K are going to vary greatly on what types of vegetables are consumed.

Answer 5

TRUE

Individuals who consume large amounts of green leafy vegetables (collards, spinach, broccoli), legumes, and some vegetable oils have a much larger intake of vitamin K

Question 6

What is the EAR for vitamin K?

Answer 6

The FNB did not find sufficient data to establish an EAR; they established AIs

Question 7

Where is the phylloquinone mainly absorbed? How much?

Answer 7

Jejunum

~15-20% of dietary phylloquinone is absorbed

Question 8

(TRUE/FALSE)

Most of the vitamin K is still on the chylomicron remnant.

Answer 8

TRUE

Question 9

What happens to the vitamin K that is on the chylomicron remnant?

Answer 9

It will be brought to the liver and repackaged into VLDL, which is similar to what we talked about with vitamin E

Question 10

(TRUE/FALSE)

VLDL, LDL, and HDL deliver vitamin K to tissue

Answer 10

TRUE

Question 11

What tissue contains the most concentrated amount of vitamin K?

Answer 11

Liver; however, it has a short-half life, so VERY LITTLE long-term storage takes place in this organ.

Question 12

Where do we find the extrahepatic tissue storage of vitamin K?

Answer 12

Adrenal glands
Lungs
Bone marrow
Kidneys
Lymph nodes

Question 13

What is the most important function of vitamin K?

Answer 13

It is required for blood clotting and stopping bleeding.

There are 13 total blood clotting proteins/factors that are involved in this process, and vitamin K is required as a coenzyme for 4 of them to be activated

Question 14

What 4 blood clotting factors require vitamin K?

Answer 14

Factors II or prothrombin
Factor VII (7)
Factor IX (9)
Factor X (10)

Question 15

Gamma glutamyl carboxylase

Answer 15

An enzyme that requires vitamin K as a coenzyme.

Question 16

What type of residues do the 4 blood clotting factors have?

Answer 16

They contain several glutamic acid residues, which MUST be carboxylated for these proteins to become “activated,” which occurs via GAMMA GLUTAMYL CARBOXYLASE ***

Question 17

The carboxylation of the 4 blood clotting factors activates the factor by doing what?

Answer 17

Gamma glutamyl carboxylase (vitamin K dependent) will add a carboxyl group, allowing for CALCIUM to bind, activating the peptide, allowing it to participate in the blood clotting process

Question 18

Which vitamin K-dependent blood clotting factors are present in the intrinsic pathway?

Answer 18

Factors II, X, XI
(All except for Factor VII)

Intrinsic pathway = in the blood

Question 19

How is a blood clot formed?

Answer 19

The cross-linking of fibrin

Question 20

What blood clotting factor is in the extrinsic pathway?

Answer 20

Factor VII
Factor X
Factor II / prothrombin

Extrinsic pathway = occurs within the tissue AND has TISSUE FACTOR

Question 21

Tissue Factor

Answer 21

Released in abundance from tissues like lungs and intestine; within the EXTRINSIC pathway

Dependent on Factor VII

Question 22

SKIP VITAMIN K CYCLE - - MAKE MANUAL CARDS TO MEMORIZE THE STEPS OF THE REACTIONS

Question 23

What interferes with vitamin K by preventing the conversion of vitamin K to its active coenzyme form?

Answer 23

Anticoagulants like warfarin

Question 24

Specifically, what enzymes does warfarin interfere with?

Answer 24

Quinone reductase
Epoxide reductase

Question 25

Besides blood clotting, what is another function of vitamin K?

Answer 25

Formation and mineralization of bones

Question 26

What 2 proteins require vitamin K that are identified in bones?

Answer 26

BGP (Bone Gla protein)

MGP (Matrix Gla protein)

*Vitamin K acts as a coenzyme for gamma-glutamyl carboxylase when the above proteins are carboxylated within the bone, this will allow them to BIND UP CALCIUM

Question 27

What causes bone hardening and increases bone mineral density?

Answer 27

BGP and MGP proteins are carboxylated within the bone, allowing them to bind additional calcium

Question 28

Where are BGP and MGP mostly secreted from?

Answer 28

The osteoblasts

Question 29

BGP and MGP contain what percent of non-collagen protein in the bone?

Answer 29

15-20%

Question 30

(TRUE/FALSE)

BGP and MGP pull calcium out of the blood and into the bone.

Answer 30

TRUE

Question 31

What happens if additional calcium cannot be taken up into bone via BGP and MGP?

Answer 31

High blood calcium will be deposited into soft tissues, and it will result in low bone density

Question 32

(TRUE/FALSE)

Vitamin K deficiency is extremely unlikely in healthy individuals.

Answer 32

TRUE

Question 33

What populations are at risk for vitamin K deficiency?

Answer 33

Newborn infants
Severe GI malabsorptive disorders
Chronic antibiotic consumption

Question 34

Why are newborn infants at risk for vitamin K deficiency?

Answer 34

Breast milk is very LOW in vitamin K
Stores are low d/t poor placental transfer
Intestinal tract bacteria are not populated
In the US, this is one of the first injections they get (0.5 to 1 mg vitamin K via IM, so they are not at risk for bleeding)

Question 35

What is the best assessment of vitamin K status?

Answer 35

Plasma prothrombin concentration

Normal: 80 to 120 micrograms/mL