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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
inhibitors of intestinal absorption of Mg
1. alcohol 2. phytic acid (traps Mg) 3. fiber 4. fatty acids
26
where does Mg go when inhibitors are present?
feces
27
with high Mg intake,
transporter is saturated, passive paracellular transport to portal blood
28
passive paracellular transport of Mg is upregulated by
calcitriol and PTH
29
when is active Mg saturable
at physiological range
30
where is Mg found in body
54% in skeleton 45% in soft tissues 1% in EC fluid
31
is Mg IC or EC
IC!
32
in what people is serum Mg rly high
vegetarians and vegans
33
__ stimulates release of Mg from bone
**PTH** stimulates release of Mg from bone
34
where is Mg lost
plenty in feces, some in urine
35
what type of treatments affect Mg
diuretics: treatments that target urinary filtration
36
what is the central organ of Mg homeostasis
kidney
37
5-15% Mg reabsorbed in __ 65-75% __ 5-10% __
5-15% Mg reabsorbed in **proximal tubule** 65-75% **thick ascending limb** 5-10% **convoluted tubule**
38
up to __% of filtrated Mg is reabsorbed
up to **95**% of filtrated Mg is reabsorbed
39
to preserve Mg, __ can be reduced to 1%
to preserve Mg, **urinary excretions** can be reduced to 1%
40
increased Mg excretion and decreased resorption caused by
diuretics alcohol
41
resorption of Mg is passive in __ active in __
resorption of Mg is passive in **thick ascending loop** active in **distal convoluted tubule**
42
during passive resorption in thick ascending loop, __ and __ inhibits __+__ increases resorption
during passive resorption in thick ascending loop, **Mg** and **Ca** inhibits **PTH + vit D** increases resorption
43
why is resorption passive in thick ascending loop but not in distal convoluted tubule
there is a voltage gradient in thick ascending loop
44
active resorption in distal convoluted tubule steps
1. TRPM6/7 brings Mg in 2. antiporter brings Na in, Mg out 3. Na out by NaK ATPase (basolateral)
45
what transporter brings Mg back into circulation?
TRPM6/7
46
How is Mg extruded into blood?
secondary active antiporter
47
How do we get Na out of cell?
primary active ATPase
48
Mg regulates cell activities by associating with organic polyphosphates (3)
ATP IP3 RNA, DNA
49
Mg binds and stabilizes these proteins
enolase, pyruvate kinase myosin (muscle contraction)
50
Mg binds and stabilizes these proteins
enolase, pyruvate kinase myosin (muscle contraction)
51
overview functions of Mg
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
role of IP3
allows Ca2+ exit
53
Mg ion trafficking 1) Mg regulates 2) Mg blocks
Mg ion trafficking 1) Mg regulates **NaK ATPase** 2) Mg blocks **Ca channels at right times**
54
why is Mg deficiency so bad?
it causes K+ deficiency which has CV effects and can be deadly
55
Mg deficiency reduced __ in skeletal muscle = K+ depletion
Mg deficiency reduced **NaK pump** in skeletal muscle = K+ depletion
56
Mg deficiency down-regulation of __ channels in heart
Mg deficiency down-regulation of **Mg-sensitive K+** channels in heart
57
Mg deficiency increased uptake and release of __ = increased __ = problems with muscle contraction
Mg deficiency increased uptake and release of **calcium** = increased **IC calcium** = problems with muscle contraction
58
Mg deficiency causes __ symptoms
Mg deficiency causes **CV** symptoms
59
CV symptoms caused by Mg deficiency
EKG changes vasospasms increased BP arrhythmia
60
is there a reliable way to assess Mg?
no
61
3 ways to assess Mg
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
why is plasma bad to assess Mg
like Ca, phosphate, Mg in plasma can look normal when tissue is low

IHN BIOCHEMISTRY FINAL (15 decks)

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