Lecture #19 - Calcium Flashcards
Primary functions of calcium?
1.Structural component of bones and teeth
2. muscle contraction
3. nerve impulse transmission
4. blood clotting
5. cofactor for enzyme activation.
Calcium absorption rate from diet?
Only 25-30% of ingested calcium is absorbed.
Why must calcium be liberated to its ionized and soluble form before absorption?
Calcium in supplements or foods is in the form of insoluble salts and must be solubilized for absorption.
How is calcium absorbed in the small intestine?
Through saturable, carrier-mediated active transport and diffusion.
What are the key components involved in the active transport of calcium?
TRPV6, CaT1, Calbindin D9k, Calcium ATP-ase pump (all vitamin D dependent).
Why is vitamin D important for calcium absorption?
It increases the expression of calcium transporters, allowing for greater calcium intake from foods.
What dietary factors limit calcium bioavailability?
Fibre, phytic acid (phytate), oxalic acid (oxalate), unabsorbed fatty acids.
What factors enhance calcium absorption?
Vitamin D, sugars, sugar alcohols, proteins.
What happens when plasma calcium concentration exceeds 10.5 mg/dL?
Parafollicular cells release calcitonin to lower circulating calcium levels.
