Mailing List Archive

Mailing List: techdiver

Message Display

>>And the saga continues... (g)
>>
>>>Scott,
>>>
>>>Let me check, but I do not think that the statement:
>>>
>>>>4) CO binding is so thermodynamically favorable that binding is, 
>>>>practically speaking, permanent, essentially removing the bound 
>>>>hemo site from the pool of available transport.
>>>
>>>is quite accurate.  At sealevel, with only 0.21 ATA of oxygen partial
>>>pressure, this statement is essentially true, but in the presence of
>>>high enough partial pressures of oxygen, monoxide will unbind from
>>>hemoglobin.  "Further more, it bind with about 230 times as much tenacity
>>>as oxygen, which is illustrated by the carbon monoxide-hemoglobin
>>>dissociation curve in Figure 41-12 (this is take from Guyton's "Textbook
>>>of Medical Physiology", page 511 and 512).  This curve is almost identical
>>>with the oxygen-hemoglobin dissociation curve, except that the pressures
>>>of the carbon monoxide shown on the abscissa are at a level 1/230 of those 
>>>on the oxygen dissociation curve.  Therefore, a carbon monoxide pressure
>>>of only 0.4 torr in the alveoli, 1/230 that of the alveolar oxygen, allows
>>>the carbon moxide to COMPETE equally wit# the hemoglobin and causes half 
to
>>>the hemoglobin in the blood to become bound with monoxide instead of 
>>oxgyen."
>>
>>Aren't we really saying the same thing?  That ratio adds up to an
>>overwhelming thermodynamic favorability for the CO binding over O2 
>>in my book.  And, barring administration of unusual and artificial 
>>driving forces to that reaction, the hemoglobin would certainly 
>>remain bound for the servicable lifetime of the molecule.  
>>Unusual and artificial driving forces such as high-pressure
>>O2, aka one treatment for CO posioning.
>>
>
>carboxyhaemoglobin half-life in air is about 5.5 hours
>
>regards,
>
>David Doolette
>ddoolett@me*.ad*.ed*.au*
>

Facinating.  I'll double check with my source, and thanks.



-------------------------------------------------------
scot@bt*.co*                                     Scot Anderson
pp000082@in*.co*        Voice: 703/761/6536
CIS:74147.2357                            Fax: 703/556/9290

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]