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HUNT241 > Lecture 5-Zinc > Flashcards

Lecture 5-Zinc Flashcards

1
Q

what are food sources of zinc

A

dairy (because we consume large amounts)

oysters and seafood

meat and poultry

organ meats like liver and kidney (found in pate and stuff)

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2
Q

what factors affect zinc bioavailability

A

host related factors
enhancers and inhibitors in meal

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3
Q

when is zinc absorption enhanced

A

zinc absorption is enhanced during pregnancy

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4
Q

in terms of zinc bioavailability what are enhancers

A

meat
fish
poultry

animal protein in general are good examples of zinc absorption enhancers

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5
Q

in terms of zinc bioavailability what are inhibitord

A

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

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6
Q

what is phytate

A

the molecule that the way in which a plant can store phosphate groups that it will need in order to germinate

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7
Q

what contains phytate

A

anything that could germinate (seeds, nuts, wholegrains, legumes, brown rice)

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8
Q

what is the structure of phytate

A

6 carbon ring structure = each has a phosphate attached to it

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9
Q

how is phytate formed

A

glucose is converted to inositol and the groups are replaced with phosphate groups attached

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10
Q

what are some inositol phosphates

A

IP6 and IP4

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11
Q

is IP6 inhibitory or not

A

powerfully inhibitory but the IP4 is not

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12
Q

what can you do to food to change it from IP6 to IP4

A

germinate the food, use fermentation also canning foods

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13
Q

what kind of ion is zinc and why does link to phytate

A

divalent positively charged ion = Zn2+

binds nicely to the two oxygen on the phytate

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14
Q

where is zinc absorbed

A

proximal small intestine

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15
Q
A
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15
Q

what are the two mechanisms for zinc absorption

A

carrier mediated transport (ZIP4)
diffusion (at high doses e.g supplements)

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16
Q

inside cells zinc is either … or ….

A

used (enzymes etc)

stored (part of meallothionein, or in vesicles, or trans-golgi network)

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17
Q

zinc is transported across basolateral membrane by

A

ZnT1

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18
Q

what does zinc bind to for transport

A

albumin
transferrin

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19
Q

if you don’t absorb all zinc what will happen with it

A

it will be excreted

20
Q

main function of zinc

A

> 200 zinc dependent enzyme

stabilises protein structure by binding to amino acid residues

participates in reaction at active site

21
Q

other zinc functions

A

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

22
Q

what are zinc fingers used by

A

1,000s of proteins

23
Q

what is the structure of zinc fingers

A

2 Cys and 2 His close together in protein chain > + zinc > protein folds tightly around it

forms a stable structure

24
Q

depending on the function of the particular protein what influence can zinc fingers have

A

enhance or repress gene transcription

25
Q

what is metallothionein

A

small cytoplasmic proteins

26
Q

what is metallothionein rich in

A

cysteine rich - bind up to 7 zinc ions at a time

27
Q

what are the functions of metallothionein

A

store zinc (high binding affinity for zinc)

zinc transporter within cell

cell signalling (especially within and between nerve cells)

protect against oxidative stress

28
Q

when and what were the first cases of zinc deficiency reported

A

1960’s in middle east = male adolescent “dwarfs”

29
Q

what were the clinical features of the first zinc reported zinc deficiencies

A

stunting = short for their age
little or no secondary sexual development

30
Q

what kind of disorder is acrodermatitis enteropathica

A

autosomal recessive disorder (need the mutation from both parents)

31
Q

what is acrodermatitis enteropathica caused by and what is the mutation that causes this

A

defective zinc absorption in small intestine

mutation of a gene that codes ZIP4 transporter on enterocytes

32
Q

what are the symptoms of acrodermatitis enteropathica

A

diarrhoea,

alopecia,

dermatitis around the mouth, nostrils, eyes and on palms and soles

poor immune function

delayed healing

33
Q

what are the inadequate dietary intake reasons for zinc deficiency

A

low energy intake
poor bioavailability
environment - low soil zinc

34
Q

what are the high physiological requirement reasons for zinc deficiency

A

growth
pregnancy
infection = immune function

35
Q

what are the excessive losses reasons for zinc deficiency

A

diarrhoea

surgery, burns

excessive alcohol consumption

36
Q

impacts of zinc deficiency of impaired growth

A

infancy = poor weight gain
children = poor linear growth

37
Q

impacts of zinc deficiency of impaired immune competence

A

increased morbidity : diarrhoea, pneumonia
increased mortality

38
Q

what are the groups at risk of zinc deficiency

A

infants, toddlers and young children

adolescents

pregnant or lactating women

“older people”

vegetarians, vegans

low socio economic status

prolonged diarrhoea

39
Q

what are the effects of zinc toxicity

A

metallic taste in mouth

nausea

gastric distress

may be fatal

40
Q

intakes above the upper level of zinc lead to what

A

reduced copper status

41
Q

what are extremely high doses of zinc

A

> 1g zinc/day

42
Q

what are intakes above the upper level of zinc

A

> 40mg/day

43
Q

what does matallothionine preferentially bind to

A

prefers to bind to copper over zinc

44
Q

how does increased zinc lead to decreased copper

A

Zn upregulates the production of metallothionine, this will bind to copper if it is available and then it is stuck in storage and the copper won’t be absorbed into the bloodstream

45
Q

what are the zinc recomendations for adult men

A

RDI : 14mg/day

EAR : 12mg/day

46
Q

what are the zinc recomendations for adult women

A

RDI : 8 mg/day

EAR : 6.5 mg/day

47
Q

what is the upper level of intake for zinc

A

40mg/day

HUNT241 (19 decks)

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