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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

A

feces

24
Q

__% Zn absorbed in typical US diet

A

20-50% Zn absorbed in typical US diet

25
Q

fractional absorption of Zn

A

10-80%

26
Q

increased Zn = __ absorption

A

increased Zn = decreased absorption

27
Q

expression and translocation of ZIP4 depends on

A

dietary Zn
increase Zn = decrease ZIP4

28
Q

increase Zn = __ copper absortion bc Zn promotes __

A

increase Zn = decreased copper absortion bc Zn promotes metallothionein induced Cu sequestration

29
Q

iron supplements = __ Zn absorption
so, pregnant women taking lots of iron should __

A

iron supplements = decreased Zn absorption
so, pregnant women taking lots of iron should also take Zn

30
Q

increased calcium in diet = __ Zn

A

increased calcium in diet = decreased Zn

31
Q

metallothionein controls __ levels
MT responds to (3)
MT made in response to high __ or __

A

metallothionein controls free Zn levels
MT responds to diet, ROS, hormones (glucocorticoids)
MT made in response to high Zn or Cu

32
Q

excess Zn blocks __

A

excess Zn blocks MT movement across enterocyte

33
Q

which is a stronger induced of MT: Zn or Cu

A

Zn
this is why Cu absorption is inhibited by excess Zn

34
Q

main plasma Zn transporter

A

albumin

35
Q

roles of Zn in cell

A
  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
Q

where does most Zn we consume end up

A

feces

37
Q

minerals (Zn, Cu, Mn, Fe, Se) are excreted

A

fecally!

38
Q

Zn plasma pool control:
under __ control
__ demands Zn

A

Zn plasma pool control:
under tight control
lactation demands Zn

39
Q

location of Zn in cells

A
  1. 50% in cytosol
  2. 30-40% bound to proteins in nucleus
  3. 10-20% found in membranes
40
Q

__% Zn excreted with feces

A

70-80% Zn excreted with feces

41
Q

in what form is Zn excreted

A

unabsorbed

42
Q

Zn secretions (3) are controlled by __

A

bile
intestinal
pancreatic secretions

ZNT5

43
Q

other losses of Zn

A

urine
hair
sweat

44
Q

overview Zn functions

A
  1. catalytic
  2. structural
  3. regulatory (gene expression: Zn fingers)
  4. superoxide dismutase
  5. immune function
  6. membrane stabolization
  7. reproduction (growth factor)
45
Q

Zn fingers
Zn binds __ in __ to allow trxn

A

Zn fingers
Zn binds MRE in promoter to allow trxn

46
Q

Zn and insulin secretion (beta-cell)

A
  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
Q

glutamate in neuron snapsis and Zn

A
  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
Q

Zn and immunity

A

Zn controls all processes in innate and active immunity

49
Q

Zn and growth

A

Zn is esssential to growth and development
Zn is linked to IGF1 (insulin-like growth factor) or its receptor

50
Q

4 options to assess Zn content

A
  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
Q

why is Zn deficiency uncommon in North America

A

bc grain is fortified

52
Q

when in life is Zn very essential

A

early in life for proper growth

53
Q

groups at risk for Zn deficiency

A
  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
Q

Zn supplements may have a positive effect on (3)

A
  1. common cold
  2. age-related macular degeneration
  3. wound healing

IHN BIOCHEMISTRY FINAL (15 decks)

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