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IHN BIOCHEMISTRY FINAL > FINAL: zinc > Flashcards

FINAL: zinc Flashcards

1
Q

3 essential trace and ultratarace elements

A

Zinc Copper Manganese

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2
Q

chemical properties of Zn, Cu, Mn

A
  • transition metals
  • electron pair acceptors/donors that complex with amino acids
  • several hundreds of enzymes and proteisn contain these metals
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3
Q

Cu or Mn deficiency affects

A

whole body systems

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4
Q

biological roles of zinc

A
  1. structural: Zn fingers, vesicular content
  2. catalytic: active site of enzymes
  3. regulatory: gene expression, signal transduction
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5
Q

determinants of biological role of Cu, Mn, Zn

A
  1. ion charge (stability and reactivity)
  2. size (limits fitting into active site)
  3. flexibility
  4. natural abundance within cell

Zn has most features

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6
Q

Zn has most features and is used widely, Cu and Mn have advantage when __ required

A

Zn has most features and is used widely, Cu and Mn have advantage when redox required

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7
Q

intestinal absorption of Zn, Mn, Cu location

A

small intestine (mainly jejunum)

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8
Q

intestinal absorption of Zn, Mn, Cu types of transport

A

1.transcellular (transport mediated, saturable, regulated)
2.paracellular (diffusion, non-regulated, only at high intake)

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9
Q

Zn form in human body

A

Zn2+

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10
Q

Zn deficiency promotes

A
  1. growth retardation
  2. poor wound healing
  3. delayed sexual maturation
  4. impaired immune function
  5. anorexia
  6. alopecia
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11
Q

Zn RDA increases during

A

pregnancy and lactation

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12
Q

reaching Zn upper limit leads to

A

Cu deficiency (which can lead to iron-deficiency anemia)

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13
Q

Zn food source

A

seafood
meat
eggs dairy

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14
Q

40-70% Zn is __
30% of Zn is __

A

40-70% Zn is animal products
30% of Zn is fortified cereals

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15
Q

Zn absorption
low intake
high intake

A

Zn absorption
low intake: carrier-mediated
high intake: paracellular diffusion

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16
Q

Zn transporters
brush border
basolateral

A

Zn transporters
brush border: ZIP4 (decreased Zn = increased ZIP4
basolateral: ZNT-1 (extrudes Zn into portal blood)

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17
Q

when does ZIP4 expression increase?

A

with low Zn

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18
Q

acrodermatitis enteropathica

A

ZIP4 inactivating mutation
leads to Zn deficiency

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19
Q

Zn storage protein

A

metallothionein (MT)

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20
Q

Zn absorption steps

A
  1. digest proteins to separate Zn (HCl, proteases)
  2. ZIP4 take Zn2+ in (DMT1 may help)
  3. ZNT-1 extrudes Zn2+ into blood
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21
Q

enhancers of Zn absorption

A
  1. organic acids (citric acid, ascorbic acid)
  2. glutathione
  3. amino acids
  4. decreased pH
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22
Q

inhibitors of Zn absorption

A
  1. phytic acid (phosphate in grain) –> cation magnet
  2. oxalic acid (leafy greens)
  3. polyphenols (coffee)
  4. select nutrients (Fe, Ca)
  5. increased pH
  6. antacids
23
Q

when inhibitors are present where does Zn go

24
Q

__% Zn absorbed in typical US diet

A

20-50% Zn absorbed in typical US diet

25
fractional absorption of Zn
10-80%
26
increased Zn = __ absorption
increased Zn = **decreased** absorption
27
expression and translocation of ZIP4 depends on
dietary Zn increase Zn = decrease ZIP4
28
increase Zn = __ copper absortion bc Zn promotes __
increase Zn = **decreased** copper absortion bc Zn promotes **metallothionein induced Cu sequestration**
29
iron supplements = __ Zn absorption so, pregnant women taking lots of iron should __
iron supplements = **decreased** Zn absorption so, pregnant women taking lots of iron should **also take Zn**
30
increased calcium in diet = __ Zn
increased calcium in diet = **decreased** Zn
31
metallothionein controls __ levels MT responds to (3) MT made in response to high __ or __
metallothionein controls **free Zn** levels MT responds to **diet, ROS, hormones (glucocorticoids)** MT made in response to high **Zn** or **Cu**
32
excess Zn blocks __
excess Zn blocks **MT movement across enterocyte**
33
which is a stronger induced of MT: Zn or Cu
Zn this is why Cu absorption is inhibited by excess Zn
34
main plasma Zn transporter
albumin
35
roles of Zn in cell
1. enzymatic activity: kinases, phosphatases, proteases 2. protein structure and stability: Zn finger, trxn factors 3. gene-expression: Zn-sensitive trxn factors, mRNA stabilization
36
where does most Zn we consume end up
feces
37
minerals (Zn, Cu, Mn, Fe, Se) are excreted
fecally!
38
Zn plasma pool control: under __ control __ demands Zn
Zn plasma pool control: under **tight** control **lactation** demands Zn
39
location of Zn in cells
1. 50% in cytosol 2. 30-40% bound to proteins in nucleus 3. 10-20% found in membranes
40
__% Zn excreted with feces
**70-80**% Zn excreted with feces
41
in what form is Zn excreted
unabsorbed
42
Zn secretions (3) are controlled by __
bile intestinal pancreatic secretions ZNT5
43
other losses of Zn
urine hair sweat
44
overview Zn functions
1. catalytic 2. structural 3. regulatory (gene expression: Zn fingers) 4. superoxide dismutase 5. immune function 6. membrane stabolization 7. reproduction (growth factor)
45
Zn fingers Zn binds __ in __ to allow trxn
Zn fingers Zn binds **MRE** in **promoter** to allow trxn
46
Zn and insulin secretion (beta-cell)
1. Zn enters vesicle (ZNT8) that already has insulin 2. insulin/Zn2+ hexamer forms 3. Zn allows packing of insulin 4. insulin/Zn is absorbed, secreted into circulation (Zn2+ is free again)
47
glutamate in neuron snapsis and Zn
1. glutamate in granule with Zn 2. released together, glutamate binds postsynaptic membrane 3. Zn can control channels in postsynaptic cell 4. Zn in postsynaptic cell binds metallothionein (MT)
48
Zn and immunity
Zn controls all processes in innate and active immunity
49
Zn and growth
Zn is esssential to growth and development Zn is linked to IGF1 (insulin-like growth factor) or its receptor
50
4 options to assess Zn content
1. serum levels (bad bc influenced by time of day, stress, infections, meds) 2. metallothionein (RBC MT decreased with low Zn) 3. urinary excretion (consistent, good for severe deficiency) 4. hair Zn content (for chronic low intake)
51
why is Zn deficiency uncommon in North America
bc grain is fortified
52
when in life is Zn very essential
early in life for proper growth
53
groups at risk for Zn deficiency
1. elderly 2. low SES 3. pregnancy 4. diabetes 5. alcoholism 6. liver disease 7. veg and vegans (consuming unrefined grains) 8. malabsorption syndromes
54
Zn supplements may have a positive effect on (3)
1. common cold 2. age-related macular degeneration 3. wound healing

IHN BIOCHEMISTRY FINAL (15 decks)

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