Mg Flashcards
what are the characteristics of Mg?
- 2nd most abundant cation in the cell
- usually bound to other ligand/molecules = chelates anionic ligands
- can bind to highly charged molecules that others can’t = stabilizers
- can compete with Ca
what is the physiological significance of Mg to other elements?
what are the physiological roles of Mg?
- essential for effective aerobic + anaerobic metabolism
- intimately involved in essential functions: energy metabolism, protein synthesis, 2nd messenger systems (hormones/neurotransmitters), stabilizer of ion channels
what role does Mg play in ADP/ATP conformation
binds to the last 2 phosphates = provides stability
what is the general role of + specific steps of glycolysis is Mg a part of
helps facilitate the reactions, reacts with the substrate + ATP
step 1: glucose -> G6P
step 3: F6P -> FBP
step 7: 1,3BPG -> 3PG
step 9: 2PG -> PEP
step 10: PEP -> pyruvate
what is the general role of Mg in the adenylate cyclase system 2nd messenger systems
activation of the Gprotein subunit needs Mg and Mg-GTP present
+ Mg binds directly to Gprotein to further enhance interaction activity
+ Mg required for ATP to drive cyclic AMP link/provide energy
what is the general role of Mg in the phosphoinositol cycle 2nd messenger systems
activation of the Gprotein subunit needs Mg and Mg-GTP present
+ Mg binds directly to Gprotein to further enhance interaction activity
+ Mg provides phospholipid substrate for PIP2 -> IP3 + DAG reaction
+ Mg-ATP drive protein kinase C step for functional effects
what other micronutrient does the PIP2 to IP3 relate to
conversion to IP3 is the activating signal for Ca release from the endoplasmic reticulum
what is the general role of Mg on ion channel function
- required for active transport of K out of the cells by ATP-pump/direct effect on K channel conformation
- ATP synthase depends on Mg for activity
- bound = allows for ion interaction / unbound = conformational change impacting interaction
what is the RDA for Mg
adults 310mg/day (female) 400mg/day (male)
- increase with age + pregnancy
what are food sources of Mg
unrefined items, green leafy veg, nuts, whole grains, legumes/tofu
how is Mg absorbed
passive + active transport systems
what factors increase Mg absorption
- low status
- low/indigestible carbs
what factors decrease Mg absorption
- increased age
- GI dysfunction
- non0-fermentable fibres
- protein
- phytates
what form of Mg is absorbed the best
citrate
what are the 2 main Mg transporters
Claudin 16/19 + TRPM6
reabsorption of Mg is driven by what
[Na], H2O, Mg [filtrate]
what organ is involved with Mg excretion/retention + where does majority happen
kidney, proximal + thick ascending tubules
how is Mg filtering different from Ca
its filtered as free not bound to a protein = most is reabsorbed
what is required for Mg reabsorption
K+ ions
what are Mg deficiency symptoms
- hypocalcemia + hypokalemia
- impaired PTH secretion + renal/skeletal resistance to PTH
- seizures, vertigo, weakness, headache
- cardiac: abnormal ECG, dysrhythmias, smooth muscle irregularities
- nausea, vomiting
what are causes of Mg deficiency
- usually a secondary disease
- impaired/decreased absorption
- kidney dysfunction
- chronic electrolyte imbalance
- osmotic/pressure diuresis (excess excretion)
