Magnesium

Question 1

Where is magnesium found in the body?
How much of it is free?

Answer 1

Majority in skeleton, then soft tissues: usually bound to ligands and molecules
1% extracellular fluid where 0.6% is free

Question 2

Magnesium acts primarily as

Answer 2

stabilizer and complexer for organic phosphates and nucleic acid

Question 3

Mg is essential for aerobic and anaerobic metabolism. Which essential functions does this include?

Answer 3

Cellular energy metabolism (lipid and carb)
Nucleic acid and Protein syn
2nd Messenger system
Ion channel (stabilizer)

Question 4

How does Mg differ from calcium

Answer 4

large hydrated volume which makes it not as flexibly in t’s binding state, though still competitive
- in water will increase “hardness”

Question 5

How is mg involved in ATP/ADP

Answer 5

Stabilizers the Phosphate tails

Question 6

Functions of Mg in glycolysis

Answer 6

activate enzyme, involved in energy making / using
makes substrates less available by temp binding

Question 7

How is Mg involved in Protein syn

Answer 7

bind specifically to the phosphate group on nucleic acids for activity and for stabilization - prevent damage and degradation

Question 8

Mg as a secondary messenger: Adenylate cyclase

Answer 8

Adenylate cyclase: G-protein bound to activate (w/GTP), to enhance interaction, to drive cAMP link, to provide energy for Kinase A

Question 9

Mg as a secondary messenger: IP3

Answer 9

Provides substate for PIP2
Inverse relationship b/w [Mg] and IP3 activation
Drives Protein Kinase C step

Question 10

Mg for ion channels

Answer 10

Needed to pump K out of cells (actively and passively)
ATP synthase

Question 11

Food sources of Mg

Answer 11

high - legumes, green leafy veg, nuts, unpolished grains
Moderate - meat, fruits, dairy

Question 12

RDA / AI for Mg

Answer 12

Infants: 30-75 AI
Men: 400-420 mg/d
Women: 310-360 mg/d
- Need more when growing - 14-18
- more when pregnant b/c of wt gain

Question 13

Absorption of Mg

Answer 13

30-50% absorbed - entire intestine but mainly in ileum and lower J.
More is absorbed when you eat less (inverse relationship - tightly reg)
Proteins + Fiber can decrease absorp

Question 14

Why would absorption of Mg not be a problem if body gets deficient?

Answer 14

Its a passive and active absorption system

Question 15

Best absorption: Carbonate, Citrate, Glycinate, Malate

Answer 15

Citrate (18% - 90 bioavail)
Glycinate (18% - 80)
Malate (6.5% - 70)
Carbonate (45% - 30)

Question 16

Excretion of Mg

Answer 16

Kidney - 70% of Mg filtered is free = increase reabsorption
75-90% reabsorbed in proximal and thick ascending tubules
***Requires K to be RE-absorbed

Question 17

Why would hypokalemia happen if Mg was deficient ?

Answer 17

keep trying to reabsorb which uses K+, which could cause K deficiency

Question 18

Why would hypocalcemia happen if Mg was deficient ?

Answer 18

PTH req adenylate cyclase = less PTH = less serum calcium = less absorption

Question 19

How would unmanaged diabetes and unmanaged BP affect Mg

Answer 19

Causes for decreased uptake
Diabetes: cause glucose in tubules = excess urine, less uptake (osmotic diuresis)
BP: high BP the body would respond by removing solvent / ANP = Pressure diuresis

Question 20

What else could cause mg deficiency

Answer 20

depletion = secondary disease
GI malabsorption, Vomit, Diarrhea
Kidney dysfxn
Chronic electrolyte imbalances