digestion and absorption

Question 1

b6 digestion/absorption

Answer 1

prior to absorption, phosphate group removed from PLP, PMP forms; absorption of pyridoxine, pyridoxal, pyridoxamine in jejunum; non saturable PASSIVE DIFFUSION

Question 2

what vitamins are passive diffusion?

Answer 2

thiamin(b1) during high intake levels, b6, nicotinic acid(niacin)

** [but don’t forget niacin is also active diffusion]

Question 3

what vitamin stored are in skeletal muscle?

Answer 3

thiamin(half of thiamin stores here, rest in heart, liver, kidney)

Question 4

thiamin digestion and absoprtion

Answer 4

food stored thiamin as phosphorylated derivative, hydrolzyed by phosphatases to release thiamin into SI. Readily absorbed by high affinity folate-thiamine transporters (SLC19A2, SLC19A3) localized to plasma membranes. exit from enterocyte by proton gradient-dependent carrier-mediated transport

UPTAKE: portal circulation to liver, then peripherally; IMMEDIATELY AFTER CELL ENTRY ASS PHOSPHATE GROUP TO HANG ONTO IT. –> phosphorylated after immediate cell entry to yield ThDP and trap metabolically, transported to mitochondria, peroxisomes, release free thiamin. **transport inhibited by alcohol consumption

Question 5

Which vitamins are no toxicity?

Answer 5

thiamin (b1), riboflavin, niacin(hard), pantothenic acid

Toxicity(folate bc u mask b12 deficiency, ), vit c, e, choline