Case 3 - micronutrients absorption

Question 1

what are the fat soluble vitamins

Answer 1

A,D,E,K

Question 2

how are these fat soluble vitamins absorbed

Answer 2

evidence of facilitated diffusion and/or endocytosis at physiological concentrations

Question 3

what does fat soluble vitamin absorption require

Answer 3

requires optimal fat digestion

Question 4

what are the water soluble vitamins

Answer 4

B group and C

Question 5

how are water soluble vitamins absorbed

Answer 5

specific transporters - facilitated and secondary

Question 6

what is VitB12 absorbed by

Answer 6

endocytosis - requires intrinsic factor and binds which is absorbed

Question 7

what is Vitamin C coupled to

Answer 7

sodium entry

Question 8

what are the two routes for Ca2+ absorption

Answer 8

transcellular and paracellular

Question 9

describe the transcellular route and what is it regulated by

Answer 9

it is on the apical side and this process is regulated by Vitamin D

Question 10

what is the route of the paracellular route

Answer 10

crosses the epithelium down the electrical gradient

Question 11

what does Ca2+ absorption enter via

Answer 11

TRPV6

Question 12

what are the two B group channels involved in calcium absorption and where

Answer 12

B6 in the small intestine
B5 in kidney

Question 13

what happens once the calcium is inside

Answer 13

it binds to a protein called calbindin

Question 14

what happens at the basolateral membrane

Answer 14

calcium is removed from the cell via active transport on the calcium pump (PMCA)

this uses ATP to pump calcium out

Question 15

what is the regulation of calcium usually done by

Answer 15

the active form of Vitamin D: 1,25-dihydroxy-Vitamin D (calcitrion)

Question 16

what does this bind to

Answer 16

intracellular receptors which triggers transcprtion of the mRNA

Question 17

what happens to the mRNA

Answer 17

transcribed and codes for 3 proteins: TRPV6 channel, calbinidin protein and the PMCA

Question 18

what are these proteins unregulated by and what does this do

Answer 18

unregulated by vitamin D to make more Calcium

Question 19

where is iron absorbed

Answer 19

in the duodenum §

Question 20

what kind of process is the iron absorption

Answer 20

transcellular process

Question 21

recount the steps of the iron absorption

Answer 21

1. dcytb reduces non heme Fe3+ to Fe2+
2. DMT co transports Fe2+ with H+
3. heme Fe2+ enters by unknown mechanisms
4. heme oxygenate oxidises the Fe2+ in heme and then releases Fe3+
5. Fe2+ tranfers to mobilferrin
6. Fe2+ leaves the cell via ferroportin (FP1) and after hephaestin oxidises it to Fe3+, the iron binds to transferrin in plasma

Question 22

what happens to biliverdin

Answer 22

changed into bilirubin

Question 23

what is the regulation by and where is it produced

Answer 23

regulated by the hormone hepcidin and is produced by the liver

Question 24

when is it produced

Answer 24

when the body has plenty of iron

Question 25

what does hepcidin bind to

Answer 25

ferroportin so you have less of these transporters and decreases iron absorption