Exam 3 Major Minerals

Calcium – Chemical Structure

Exists as Ca2+ ion and hydroxyapatite Ca10(PO4)6(OH)2 in bone

Calcium – Functional Distribution

99 percent in bone and teeth 1 percent in extracellular and intracellular fluid

Calcium – Digestion Requirement

No enzymatic digestion requires gastric acid HCl to solubilize calcium salts into Ca2+

Calcium – Gastric Influence

Higher stomach acidity increases solubility and absorption lower acidity decreases absorption

Calcium – Active Absorption Site

Duodenum and proximal jejunum

Calcium – Passive Absorption Site

Ileum and throughout intestine

Calcium – Active Transport Entry

TRPV6 channel transports Ca2+ into enterocyte

Calcium – Intracellular Transport Protein

Calbindin D9k binds Ca2+ and facilitates movement across enterocyte

Calcium – Basolateral Exit Pump

PMCA1b Ca ATPase actively transports Ca2+ into blood

Calcium – Secondary Exit Transporter

NCX1 sodium calcium exchanger moves Ca2+ out of cell

Calcium – Passive Absorption Mechanism

Paracellular diffusion driven by electrochemical gradient

Calcium – Absorption Regulation

Upregulated by calcitriol 1

Calcium – Absorption Enhancers

Vitamin D lactose acidic environment adequate protein

Calcium – Absorption Inhibitors

Phytates oxalates fiber fatty acids excess magnesium zinc

Calcium – Fat Malabsorption Effect

Calcium binds fatty acids forming insoluble soaps reducing absorption

Calcium – Blood Transport Ionized

50 percent free Ca2+ biologically active

Calcium – Blood Transport Protein Bound

40 percent bound to albumin

Calcium – Blood Transport Complexed

10 percent bound to citrate phosphate

Calcium – Hormone PTH

Increases bone resorption renal Ca reabsorption activates vitamin D

Calcium – Hormone Calcitriol

Increases TRPV6 and calbindin expression increasing absorption

Calcium – Hormone Calcitonin

Inhibits osteoclast activity lowers blood calcium

Calcium – Bone Remodeling

Osteoclasts resorb bone osteoblasts deposit calcium

Calcium – Tissue Uptake Mechanism

Voltage gated Ca2+ channels allow cellular entry

Calcium – Intracellular Storage

Sarcoplasmic reticulum and mitochondria

Calcium – Intracellular Regulation

Ca ATPase pumps and Na Ca exchangers maintain low cytosolic Ca

Calcium – Signaling Mechanism

PLC converts PIP2 to IP3 and DAG IP3 releases Ca from ER

Calcium – Muscle Mechanism

Ca binds troponin causing actin myosin interaction

Calcium – Nerve Mechanism

Ca influx triggers neurotransmitter vesicle fusion

Calcium – Clotting Mechanism

Required for activation of clotting factors factor IV

Calcium – Renal Reabsorption Site

Distal tubule via TRPV5

Calcium – Renal Regulation

PTH increases Ca reabsorption kidneys fine tune levels

Calcium – Excretion

Urine feces sweat

Calcium – Sodium Interaction

High sodium intake increases urinary calcium loss

Calcium – Recommended Intake

1000 to 1200 mg per day

Calcium – Deficiency Mechanism

Secondary hyperparathyroidism increases bone breakdown

Calcium – Deficiency Diseases

Rickets osteomalacia osteoporosis tetany

Calcium – Toxicity Mechanism

Excess calcium leads to hypercalcemia and calcification

Calcium – Toxicity Syndrome

Calcium alkali syndrome

Calcium – Assessment

DEXA scan serum calcium limited indicator

Phosphorus – Chemical Form

Exists as phosphate PO4 3 minus

Phosphorus – Digestion

Released from organic compounds in stomach and intestine no enzymatic digestion required for free phosphate

Phosphorus – Absorption Site

Small intestine

Phosphorus – Active Transporter

NaPi IIb sodium phosphate cotransporter

Phosphorus – Passive Absorption

Paracellular diffusion

Phosphorus – Absorption Regulation

Increased by calcitriol decreased by high calcium intake

Phosphorus – Transport

Circulates as inorganic phosphate in plasma

Phosphorus – Storage

Primarily in bone with calcium

Phosphorus – Renal Transporters

NaPi IIa and NaPi IIc reabsorb phosphate in proximal tubule

Phosphorus – Hormone PTH

Decreases renal phosphate reabsorption increases excretion

Phosphorus – Hormone FGF23

Reduces phosphate reabsorption and suppresses vitamin D activation

Phosphorus – Function ATP

Energy storage and transfer

Phosphorus – Function Membrane

Component of phospholipids

Phosphorus – Function DNA RNA

Structural backbone

Phosphorus – Function Buffer

Intracellular buffering system

Phosphorus – Mechanism

Phosphorylation regulates enzyme activity

Phosphorus – Excretion

Kidneys primary route

Phosphorus – Recommended Intake

700 mg per day adults

Phosphorus – Deficiency

Rare weakness impaired ATP production

Phosphorus – Toxicity

Hyperphosphatemia causes hypocalcemia and calcification

Phosphorus – Assessment

Serum phosphate Ca P ratio

Magnesium – Chemical Nature

Divalent cation Mg2 plus

Magnesium – Distribution

50 to 60 percent bone remainder intracellular less than 1 percent extracellular

Magnesium – Digestion

Released from food matrix no enzymatic digestion

Magnesium – Passive Absorption

Paracellular diffusion when intake high

Magnesium – Active Transporters

TRPM6 and TRPM7 channels

Magnesium – Absorption Site

Small intestine ileum and colon

Magnesium – Absorption Regulation

Upregulated during deficiency

Magnesium – Absorption Inhibitors

Phytates high calcium zinc fatty acids

Magnesium – Transport

Free protein bound and complexed

Magnesium – Tissue Uptake

Via channels driven by electrochemical gradient

Magnesium – Storage

Bone and intracellular compartments

Magnesium – Function ATP

Forms Mg ATP complex essential for energy metabolism

Magnesium – Function Enzyme

Cofactor for kinases including hexokinase and phosphofructokinase

Magnesium – Function Neuromuscular

Regulates Ca entry prevents over excitation

Magnesium – Mechanism

Stabilizes nucleic acids and ATP

Magnesium – Renal Reabsorption

Loop of Henle and distal tubule

Magnesium – Excretion

Kidneys

Magnesium – Recommended Intake

310 to 420 mg per day

Magnesium – UL

350 mg per day supplements

Magnesium – Deficiency

Hypomagnesemia causes tetany arrhythmias

Magnesium – Toxicity

Hypermagnesemia causes hypotension cardiac arrest

Magnesium – Assessment

Serum Mg limited RBC Mg sometimes used

Potassium – Chemical Nature

Monovalent cation K plus

Potassium – Distribution

98 percent intracellular

Potassium – Absorption

Passive diffusion and K H ATPase

Potassium – Transporter

Na K ATPase maintains gradient

Potassium – Tissue Uptake

Stimulated by insulin and epinephrine

Potassium – Storage

No true storage intracellular pool only

Potassium – Function Nerve

Maintains resting membrane potential

Potassium – Function Muscle

Controls contraction

Potassium – Function Cardiac

Regulates heart rhythm

Potassium – Mechanism

Electrochemical gradient

Potassium – Acid Base

K H exchange across membranes

Potassium – Renal Secretion

Distal tubule via aldosterone and ROMK channels

Potassium – Excretion

Kidneys feces sweat

Potassium – Recommended Intake

2600 to 3400 mg per day

Potassium – Deficiency

Hypokalemia weakness arrhythmia

Potassium – Toxicity

Hyperkalemia cardiac arrest

Potassium – Assessment

Serum potassium

Sodium – Chemical Nature

Monovalent cation Na plus