physiology questions???

[cutedoc12]

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Q1 in the resting state in man the avg difference bw the o2 content of arterial and venous blood is......5 volumes percent.....how is it calculated?????

Q2 the absorption of calcium from the small intestine is increased by.....lowering the ph in the intestine.....how??

Q3 the concentration of which of the following amino acids can be used as an estimation of the amount of collagen present in a tissue?
hydroxyproline
proline

Q4 which of the following may normally leave the bodyby the way of lungs??
lipids
acetone
glucose
chlorides

can anyone explain ????......

 

[DragonWell]

Q1 in the resting state in man the avg difference bw the o2 content of arterial and venous blood is......5 volumes percent.....how is it calculated?????

Q2 the absorption of calcium from the small intestine is increased by.....lowering the ph in the intestine.....how??

Q3 the concentration of which of the following amino acids can be used as an estimation of the amount of collagen present in a tissue?
hydroxyproline
proline

Q4 which of the following may normally leave the bodyby the way of lungs??
lipids
acetone
glucose
chlorides

can anyone explain ????......

1)?what's a volume percent?

2)I don't have a reference for this, but just thinking it through...Calcium in food is usually found as a salt - ie. calcium carbonate in Tums. In order to be absorbed, the Ca must be liberated from the salt, so you have to ionize the Ca with stomach acid. In calcium citrate, you've bound your calcium to a weak acid which should ionize easier and thus make the calcium more absorbable.


3)Proline and lysine undergo post-translational modification which adds an OH group, making them hydroxyproline and hydroxylysine. Hydroxyproline and hydroxylysine are more or less unique to collagen, thus the amount of hydroxyproline could be used to estimate the amount of collagen. This rxn requires vit. C as a cofactor, which explains the loose teeth, capillary fragility, etc seen in scurvy. Without vit C, there is no hydroxylation, and collagen can't be cross-linked.

4)Don't have any real mechanism for why this is, but when you're burning fatty acids and making ketones in the liver, the acetoacetate and B-hydroxybutyrate can go to peripheral tissues, be converted to Acetyl CoA and enter the TCA cycle. Some of the acetoacetate spontaneously breaks down into acetone which is volatile and gets blown off by the lungs.

 

[SeventhSon]

For #1, someone correct me if I'm wrong, but I believe the difference in oxygen tension is determined by the homogeneity of the ventilation/perfusion ratio from the apex of the lung to the base, and in normal circumstances with a person standing straight up, the difference is 5 Torr (i am almost positive that there is no way to calculate this number a priori). In extreme circumstances other things can affect this number (shunting, hypoxic vasoconstriction, and diffusion limitation)

For #2, someone asked this a long time ago and someone brought up a reference that claimed that there was some type of endocrine mechanism going on here, although DragonWell's explanation does make total sense.

H+ stimulates secretion by gastric/intestinal endocrine cells and this affects cholecalciferol and calcitonin levels somehow, which affect Ca reabsorption. I would not trust what I'm saying but hopefully someone out there can clarify because this exact question was asked a year ago or so.

1)?what's a volume percent?

2)I don't have a reference for this, but just thinking it through...Calcium in food is usually found as a salt - ie. calcium carbonate in Tums. In order to be absorbed, the Ca must be liberated from the salt, so you have to ionize the Ca with stomach acid. In calcium citrate, you've bound your calcium to a weak acid which should ionize easier and thus make the calcium more absorbable.


3)Proline and lysine undergo post-translational modification which adds an OH group, making them hydroxyproline and hydroxylysine. Hydroxyproline and hydroxylysine are more or less unique to collagen, thus the amount of hydroxyproline could be used to estimate the amount of collagen. This rxn requires vit. C as a cofactor, which explains the loose teeth, capillary fragility, etc seen in scurvy. Without vit C, there is no hydroxylation, and collagen can't be cross-linked.

4)Don't have any real mechanism for why this is, but when you're burning fatty acids and making ketones in the liver, the acetoacetate and B-hydroxybutyrate can go to peripheral tissues, be converted to Acetyl CoA and enter the TCA cycle. Some of the acetoacetate spontaneously breaks down into acetone which is volatile and gets blown off by the lungs.

 

[cutedoc12]

thanx again 4 ur inputs....

 

[rox]

Hydroxyproline is found exclusively is collagen.

Acetone is responsible for the fruity smell of patient with DKA.