Minerals Flashcards
Major minerals
- -Calcium
- -Phosphorus
- -Potassium
- -Sodium
- -Chloride
- -Magnesium
Trace minerals (
- -Iron
- -Zinc
- -Copper
- -Manganese
Ultratrace minerals (
- -Selenium
- -Molybdenum
- -Iodine
- -Chromium
Functions of minerals
- -Maintain osmotic balance
- -Maintain charge/concentration gradients across membrane
- -Enzyme cofactors
- -Structure
- -Taste
What is the major extracellular cation?
Sodium
What is the major intracellular cation?
Potassium
Dietary sources of calcium
Dairy, seafood, turnips, broccoli, kale, dietary supplements
Most abundant metal in the body?
Calcium. About 1.4 Kg in 70 kg man
Functions of calcium
–Bone mineralization
–Signaling molecule for muscle contraction
–Helps regulate
metabolism
Blood clotting
What regulates absorption of calcium?
Calcitriol (Vitamin D)
What chaperones calcium within the cell
Calbindin
What helps increase absorption of calcium?
Vitamin D, sugars, sugar alcohols, protein
What decreases absorption of calcium?
Fiber, phytic acid, oxalic acid, other divalent cations, unabsorbed fatty acids
What increases expression of calcium channel TRPV6 at brush border and alters tight junction permeability to calcium?
Activated VDR
[Ca++] in the blood
8.5-10 mg/dL
40% bound to protein
50% free ionized
10% complexed with sulfate, phosphate, citrate etc.
Cytosolic [Ca++] vs. extraceullular
Very low in cytosol (100nMol).
10,000x higher in extraceullular area (2.3 mmol)
Where is Ca++ stored in cells?
Intracellular compartments
Ca++/ 3Na+ transporter
- -Helps export calcium from cells
- -Low affinity, high capacity
Ca++/2H+ transporter
- -Helps export calcium from cells
- -High affinity, low capacity
Calmodulin
Mediated intracellular signalling by calcium. Protein whose association with other proteins is regulated by calcium binding
What happens when intracellular calcium increased?
Glycogen synthase inactivated and glycogen phosphorylase is activated
Calcium interactions with other dietary components
- -Calcium blocks phosphorus uptake
- -Calcium transiently blocks iron uptake
- -Calcium can trap fatty acids, bile salts in “soaps” that are not digestible
Calcium excretion
- -Urinary: 100-240 mg/day (controlled by calcitriol)
- -Feces: 45-100 mg/day
- -Sweat: 60 mg/day
People at risk of calcium deficiency
- -Fat malabsorption disorders
- -Immobilized patients
Causes of calcium deficiency
Rickets
Tetany
Osteoporosis
Calcium deficiency associated with what?
Colorectal cancer
Hypertension
Type II diabetes
Calcium TUL
2,500 mg/day
Acute calcium toxicity
Constipation, bloating
Chronic calcium toxicity
Calcification of tissue, hypercalciuria, kidney stones, maybe CV disease
Best assessment of calcium status?
Bone density scan
Magnesium dietary sources
Nuts, legumes, whole grains, chlorophyll, chocolate, hard water
Magnesium functions
- -Calcium metabolism
- -Component of bone
- -Muscle contraction
- -Nerve impulse propagation
- -Cofactor in ATPases
- -Needed for kinases and polymerases that use nucleotide triphosphates
- -Needed for activation of Vit D by 25-hydroxlase
Magnesium in body
25 grams
–50-60% in bone, 40-50% in soft tissues, 1% in extracellular fluid
What allows for saturable transport of magnesium across the brush border?
TRPM6
Basolateral transport of magnesium
2Na+/Mg++ antiporter, 2K+/3Na+ ATPase
Is paracellular diffusion of magnesium saturable?
No
How much of the magnesium intracellularly is associated with ATP?
Greater than 90%
Interactions of magnesium with other things in the diet?
- -Can mimic Ca++ and compete for absorption in the kidney
- -Inhibits phosphorus absorption
Best measurement of magnesium status?
Rena Mg++ excretion before and after a loading dose
Magnesium deficiency
- -Dietary deficiency not described (can be induced though)
- -Nausea, vomiting , HA, anorexia. Progresses to seizures, ataxia, fibrillation
- -Chronic deficiency associated w/HTN and DMII