Lecture 5-Zinc Flashcards
what are food sources of zinc
dairy (because we consume large amounts)
oysters and seafood
meat and poultry
organ meats like liver and kidney (found in pate and stuff)
what factors affect zinc bioavailability
host related factors
enhancers and inhibitors in meal
when is zinc absorption enhanced
zinc absorption is enhanced during pregnancy
in terms of zinc bioavailability what are enhancers
meat
fish
poultry
animal protein in general are good examples of zinc absorption enhancers
in terms of zinc bioavailability what are inhibitord
if you are taking high doses of iron this will inhibit zinc absorption, especially if supplement is taken between meals
phytate
combination of phytate and calcium = together this even more inhibitory
what is phytate
the molecule that the way in which a plant can store phosphate groups that it will need in order to germinate
what contains phytate
anything that could germinate (seeds, nuts, wholegrains, legumes, brown rice)
what is the structure of phytate
6 carbon ring structure = each has a phosphate attached to it
how is phytate formed
glucose is converted to inositol and the groups are replaced with phosphate groups attached
what are some inositol phosphates
IP6 and IP4
is IP6 inhibitory or not
powerfully inhibitory but the IP4 is not
what can you do to food to change it from IP6 to IP4
germinate the food, use fermentation also canning foods
what kind of ion is zinc and why does link to phytate
divalent positively charged ion = Zn2+
binds nicely to the two oxygen on the phytate
where is zinc absorbed
proximal small intestine
what are the two mechanisms for zinc absorption
carrier mediated transport (ZIP4)
diffusion (at high doses e.g supplements)
inside cells zinc is either … or ….
used (enzymes etc)
stored (part of meallothionein, or in vesicles, or trans-golgi network)
zinc is transported across basolateral membrane by
ZnT1
what does zinc bind to for transport
albumin
transferrin
if you don’t absorb all zinc what will happen with it
it will be excreted
main function of zinc
> 200 zinc dependent enzyme
stabilises protein structure by binding to amino acid residues
participates in reaction at active site
other zinc functions
gene expression (zinc fingers)
tissue and cell growth (regulate protein synthesis)
cell membrane integrity
cell replication
bone formation
immune function
associated with insulin
taste acuity
what are zinc fingers used by
1,000s of proteins
what is the structure of zinc fingers
2 Cys and 2 His close together in protein chain > + zinc > protein folds tightly around it
forms a stable structure