Calcium and Phosphorussy Flashcards
What is unique about Calcium valence electrons ?
2+, lost readily in solution
large effective radius
attracts H2O
What is the calcium generally considers for in the body?
a tool or carrier (messenger)
initiates a series of processes
Bone mineralization is a huge storage for
99% of calcium
80-90% of phosphorus
Only 1% of Calcium is ionized and is responsible for?
Blood clotting - Platelets
Enzyme regulation - calmodulin
Blood clotting, nerves, muscles,
membrane permeability - bind membranes and change conformation
What is the purpose of IP3 (inositol triphosphate) and DAG
signal transduction and lipid signaling
How is IP3 made, what does it do?
Through phosphorylation of PI and hydrolysis of PIP2 (cofactor magnesium)
Allows more intracellular calcium by binding the channel
How can calcium leave the cytoplasm of a cell?
Through Na+ or Mg+ pumps/ ATPase or can be sequestered into cells (ER, mito, nucleus)
Unique characteristics of phosphorus
found in the bone as hydroxyapatite Ca10(OH)2(PO4)6
preferred ionic state is orthophosphate as HPO4 and H2PO4
at pH 7.4
ratio is 4:1
HPO4 (basic) to H2PO4 (acidic)
Biological fxn of Phosphate
Bone mineralization
Electrolyte homeostasis
Structural role (phosphates, DNA/RNA - alt with pentose sugars)
Secondary messenger - kinase, phosphates, cAMP
Vit B metabolism
How can phosphate act as a buffer?
by collecting H+ and decreasing acidity inside the cell
3 ways calcium can be absorbed small I
Duodenum - Transcellular (major route) - Rq, energy + channel+ BPcalbindin — stim by low Calcium and calcitriol (Vit D)
illenum/jejunum - paracellular - energy independent (passive), depends on concentration
Colonic fermentation - fibers release Ca2+ (4-10% can be absorbed this way)
How is phosphate absorbed by the body
Absorbed linearly as HPO4, similarly to Ca2+
- Diffusion
-Carrier mediated with Mg / Na
How effective is absorption in comparison of Calcium to Phosphate
Calcium is 20-30%
Phosphate is 60-70%
What controls PTH production and secretion
plasma Ca 2+
What are the actions of PTH
Stimulates bone osteoblast – trigger breakdown
Stimulates kidney tubular cells to increase Ca2+ absorb
Stims kidneys to increase conversion to in kidneys to Active Vit D
Increase in intestine + bloodstream absorb
- Actions are indirectly done via second messenger