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IHN BIOCHEMISTRY FINAL > FINAL: magnesium > Flashcards

FINAL: magnesium Flashcards

1
Q

Mg is a __ metal that makes __ ions in solution

A

Mg is a divalent metal that makes positive ions in solution

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2
Q

after K+, Mg2+ is the most abundant __ ion

A

after K+, Mg2+ is the most abundant intracellular ion

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3
Q

Mg is more __ and less __ than Ca

A

Mg is more hydrated and less flexible than Ca

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4
Q

since Mg is very hydrated,

A

Mg must be dehydrated to be used

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5
Q

Mg mainly binds to __

A

Mg mainly binds to phosphate (like in ATP)

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6
Q

3 properties of Mg

A
  1. binds organic anions (ATP, nucleotides)
  2. binds enzymes to alter catalytic activity
  3. competes with calcium for binding sites
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7
Q

2 functions of ATP

A

energy
make DNA, RNA

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8
Q

Mg blocks __ to regulate it

A

Mg blocks calcium to regulate it

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9
Q

dietary source of Mg

A

ALL plant and animal foods
green leafy veg (chlorophyll)
fish
nuts

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10
Q

what type of grain is best for Mg?

A

whole grains bc polished grains have depleted Mg

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11
Q

is Mg a nutrient of concern?

A

YES

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12
Q

__% of Americans don’t get enough Mg

A

48% of Americans don’t get enough Mg

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13
Q

when does Mg RDA increase

A

pregnancy, not lactation

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14
Q

is Mg non-toxic?

A

yes

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15
Q

does Mg have an upper limit?

A

yes

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16
Q

signs of Mg toxicity

A

diarrhea
nausea
flushing
double vision
muscle weakness (Ca2+ related)

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17
Q

excessive Mg intake causes

A

diarrhea and dehydration (Mg is found in some laxatives)

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18
Q

intestinal fractional absorption of Mg is __ related to intake

A

intestinal fractional absorption of Mg is inversely related to intake

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19
Q

higher intake of Mg = __ absorption

A

higher intake of Mg = decreased absorption

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20
Q

__% Mg absorbed

A

30-50% Mg absorbed

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21
Q

Mg absorption is good in __ but decreases with __

A

Mg absorption is good in children but decreases with age

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22
Q

where in intestine is Mg absorbed?

A

distal jejunum and ileum

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23
Q

intestinal absorption of Mg steps

A
  1. digestion separates Mg from proteins
  2. TRPM6 (apical) lets Mg into cell (no chaperone needed)
  3. Mg exits into blood, Na enters cell (antiporter)
  4. ATPase sends Na out
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24
Q

main type of Mg in blood

A

free Mg

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25
Q

inhibitors of intestinal absorption of Mg

A
  1. alcohol
  2. phytic acid (traps Mg)
  3. fiber
  4. fatty acids
26
Q

where does Mg go when inhibitors are present?

A

feces

27
Q

with high Mg intake,

A

transporter is saturated, passive paracellular transport to portal blood

28
Q

passive paracellular transport of Mg is upregulated by

A

calcitriol and PTH

29
Q

when is active Mg saturable

A

at physiological range

30
Q

where is Mg found in body

A

54% in skeleton
45% in soft tissues
1% in EC fluid

31
Q

is Mg IC or EC

A

IC!

32
Q

in what people is serum Mg rly high

A

vegetarians and vegans

33
Q

__ stimulates release of Mg from bone

A

PTH stimulates release of Mg from bone

34
Q

where is Mg lost

A

plenty in feces, some in urine

35
Q

what type of treatments affect Mg

A

diuretics: treatments that target urinary filtration

36
Q

what is the central organ of Mg homeostasis

A

kidney

37
Q

5-15% Mg reabsorbed in __
65-75% __
5-10% __

A

5-15% Mg reabsorbed in proximal tubule
65-75% thick ascending limb
5-10% convoluted tubule

38
Q

up to __% of filtrated Mg is reabsorbed

A

up to 95% of filtrated Mg is reabsorbed

39
Q

to preserve Mg, __ can be reduced to 1%

A

to preserve Mg, urinary excretions can be reduced to 1%

40
Q

increased Mg excretion and decreased resorption caused by

A

diuretics
alcohol

41
Q

resorption of Mg is passive in __
active in __

A

resorption of Mg is passive in thick ascending loop
active in distal convoluted tubule

42
Q

during passive resorption in thick ascending loop,
__ and __ inhibits
__+__ increases resorption

A

during passive resorption in thick ascending loop,
Mg and Ca inhibits
PTH + vit D increases resorption

43
Q

why is resorption passive in thick ascending loop but not in distal convoluted tubule

A

there is a voltage gradient in thick ascending loop

44
Q

active resorption in distal convoluted tubule steps

A
  1. TRPM6/7 brings Mg in
  2. antiporter brings Na in, Mg out
  3. Na out by NaK ATPase (basolateral)
45
Q

what transporter brings Mg back into circulation?

A

TRPM6/7

46
Q

How is Mg extruded into blood?

A

secondary active antiporter

47
Q

How do we get Na out of cell?

A

primary active ATPase

48
Q

Mg regulates cell activities by associating with organic polyphosphates (3)

A

ATP
IP3
RNA, DNA

49
Q

Mg binds and stabilizes these proteins

A

enolase, pyruvate kinase
myosin (muscle contraction)

50
Q

Mg binds and stabilizes these proteins

A

enolase, pyruvate kinase
myosin (muscle contraction)

51
Q

overview functions of Mg

A
  1. energy metabolism (binds ATP to stabilize)
  2. nucleic acid and protein synthesis
  3. secondary messenger (IP3 allows Ca2+ exit)
  4. regulate ion channels (mainly Ca2+)
52
Q

role of IP3

A

allows Ca2+ exit

53
Q

Mg ion trafficking
1) Mg regulates
2) Mg blocks

A

Mg ion trafficking
1) Mg regulates NaK ATPase
2) Mg blocks Ca channels at right times

54
Q

why is Mg deficiency so bad?

A

it causes K+ deficiency which has CV effects and can be deadly

55
Q

Mg deficiency
reduced __ in skeletal muscle = K+ depletion

A

Mg deficiency
reduced NaK pump in skeletal muscle = K+ depletion

56
Q

Mg deficiency
down-regulation of __ channels in heart

A

Mg deficiency
down-regulation of Mg-sensitive K+ channels in heart

57
Q

Mg deficiency
increased uptake and release of __ = increased __ = problems with muscle contraction

A

Mg deficiency
increased uptake and release of calcium = increased IC calcium = problems with muscle contraction

58
Q

Mg deficiency causes __ symptoms

A

Mg deficiency causes CV symptoms

59
Q

CV symptoms caused by Mg deficiency

A

EKG changes
vasospasms
increased BP
arrhythmia

60
Q

is there a reliable way to assess Mg?

A

no

61
Q

3 ways to assess Mg

A
  1. plasma (most used, not sens and spec)
  2. RBC levels (better long term)
  3. urinary excretion (~80% IV Mg load normall excreted, less is bad)
62
Q

why is plasma bad to assess Mg

A

like Ca, phosphate, Mg in plasma can look normal when tissue is low

IHN BIOCHEMISTRY FINAL (15 decks)

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