Lecture 80 Flashcards
About __ of calcium ions (Ca2+) are absorbed from intestine
1mg/day
About 1mg/day of calcium ions (Ca2+) are absorbed from intestine. Compared to how much is in the diet, this is a __ amount
small –> we can say that calcium absorption is poor
most of the daily intake of calcium is (2):
(1) Excreted in feces (90%)
(2) Excreted in urine (10%)
When talking about intestine, absorb is when
calcium goes from food inside the intestine and travels to the extracellular fluid and blood circulation
When talking about intestine (and calcium): reabsorb is when:
it goes from extracellular fluid back into intestine
The normal Ca2+ concentration in blood plasma is about:
2.4 mmol/litre
The normal Ca2+ concentration in blood plasma is about 2.4 mmol/litre. It is present in three forms:
(1) Free Ca^2+ (50%): Ionized, unbound, and easily diffuses through membranes; most important Ca form for body functions.
(2) Bound to plasma proteins (40%): Cannot diffuse through capillary membranes, remains in circulation.
(3) Bound to citrate or phosphate (10%): Diffuses through capillary membranes, readily available for cellular use.
50% of calcium is:
Ionized, unbound, and easily diffuses through membranes; most important Ca form for body functions.
the most important Ca form for body functions:
free Ca2+ (accounts for 50% of calcium in blood plasma)
40% of Ca2+ is (2):
(1) bound with plasma proteins
(2) cannot diffuse through capillary membranes, remains in circulation
Up to 40% of Ca2+ is bound with plasma proteins. In this form calcium it is
not able to diffuse through capillary membrane, so it stays in circulation.
Up to 10% of Ca2+ is
bound with citrate or phosphate.
Up to 10% of Ca2+ is bound with citrate or phosphate. In these forms:
It can diffuse through capillary membranes, so easier for cells to use it.
About __ of phosphate ions from diet are absorbed from intestine and transport into blood.
1mg/day
What is more efficient in terms of absorption? calcium or phosphate ions
phosphate absorption is much more efficient than Ca2+.
After absorption, phosphate is present in blood plasma in two forms:
- In the form of HPO4-2, 1.05 mmol/litre.
- In the form of H2PO4-1, 0.26 mmol/litre.
The ratio of $HPO_4^{-2}$ to $H_2PO_4^{-1}$ is
is pH-dependent
The ratio of $HPO_4^{-2}$ to $H_2PO_4^{-1}$ is pH-dependent; acidic conditions favor
H2po4-1
What happens when pH of the extracellular fluid is more acidic in terms of phosphate ions?
concentration of HPO42- decreases with relative increase of H2PO4-1
In excess (greater than critical value of 1 mmol/litre), phosphates are
excreted in urine
If phosphate concentration is below critical value (1mmol/litre), all phosphates are :
reabsorbed (they go from the urine, through kidney and back into extracellular fluid), there is no loss into urine.
If phosphate is above critical value, excretion in urine is proportional to:
the increase of phosphate concentration.
What is a reservoir for phosphate in the ionic forms?
bones
Ca2+ and phosphate ions can go back and forth to
bone depending on the need.
