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Q: subcellular pH across human cell types ( No Answer,   1 Comment )
Subject: subcellular pH across human cell types
Category: Science > Biology
Asked by: ryandoherty-ga
List Price: $50.00
Posted: 16 May 2006 23:30 PDT
Expires: 15 Jun 2006 23:30 PDT
Question ID: 729645
I have always wondered how pH varies within human cells, but haven't had
the time to look into this thoroughly.  Can someone provide me with
the pH of subcellular compartments within human cells, as well as how
pH differs across cell types?  Can you also include scientific
references for your findings?  Thanks.

Request for Question Clarification by crabcakes-ga on 13 Jun 2006 22:36 PDT
Hi Ryandoherty,

   Is this the type of information you are seeking?

?The maintenance of chondrocyte pH is an important parameter
controlling cartilage matrix turnover rates. Previous studies have
shown that, to varying degrees, chondrocytes rely on Na(+)/H(+)
exchange to regulate pH. HCO(3)(-)-dependent buffering and
HCO(3)(-)-dependent acid-extrusion systems seem to play relatively
minor roles. This situation may reflect minimal carbonic anhydrase
activity in cartilage cells. In the present study, the pH regulation
of the human chondrocyte cell line, C-20/A4 has been characterised.
Intracellular pH (pH(i)) was measured using the H(+)-sensitive
fluoroprobe BCECF.?

?Regulating pH at about 7.4 is important for normal cellular function.
pH is a log scale of relative amounts of H+ and OH-. The scale runs
from 0 (acidic) to 14 (basic) with 7 being neutral (=having an equal
amount of H+ and OH- ions). Buffers, such as Hb, other proteins,
phosphates, and bicarbonates, are substances that cushion a solution
from abrupt pH changes.
4. The lung and the distal tubules of the kidney are responsible for
regulating blood pH. Acidosis and Alkalosis occur when pH drifts away
from 7.4, which results from either a respiratory (e.g.,
hyperventilation) or metabolic (e.g., excessive vomiting) imbalance.?

?The pH of the cytosol within a human cell is about 7.4. BUT, this
value masks the pH differences that are found in various compartments
within the cell. For example,
?	The interior of lysosomes is much more acidic (as low as pH 4) than
the cytosol, and the enzymes within work best at these low pH values.
?	The pH differential created within chloroplasts by the energy of the
sun is harnessed to synthesize ATP which, in turn, powers the
synthesis of food. (Discussion)
?	The pH differential created within mitochondria during the
respiration of food is harnessed to the synthesis of ATP which, in
turn, powers most of the energy-consuming activities of the cell such
as locomotion and biosynthesis of cell components.?

Please let me know if I am on the right track!

Reggards, Crabcakes
There is no answer at this time.

Subject: Re: subcellular pH across human cell types
From: elmindreda-ga on 13 Jun 2006 10:31 PDT
pH of organelles (subcellular structures) are briefly explained in the
PubMed article published by the Department of Molecular and Cell
Biology, University of California, Berkeley.

The article is called "Organelle pH studies using targeted avidin and

Hope that helps. :D

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