Talk:Carbonic anhydrase
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spontaneous conversion of CO2<->HCO3
Should the arrows in the reaction be reversible arrows? Respiration maintains pH and shifts this reaction in blood all the time. Correct? — Preceding unsigned comment added by 131.247.244.173 (talk) 16:27, 7 September 2011 (UTC)
[1]: "This reaction (carbonation) occurs spontaneously in aqueous solution, but does so slowly."
- If carbonation were spontaneous, then it would be stable. It's isn't. That's why pop goes flat. That's not to say that carbonates of metals in water aren't stable. Alkaline water is a medium for spontaneous carbonatation. 216.234.170.106 05:24, 19 July 2006 (UTC)
- The interconversion of CO2 and bicarbonate/carbonate is indeed spontaneous, and soda-pop goes flat because it reaches equilibrium. Pop is kept supersaturated with CO2 under pressure, when the pressure is removed, the supersaturated CO2 rapidly bubbles out (minutes to hours); this effervescence is delightful but unfortunately transient. When it is "flat" it is at equilibrium. The relative amounts of bicarbonate and CO2 in pop is not too important here, as pop is very acidic and bicarbonate (and carbonate) is practically absent.
In neutral or alkaline solutions, bicarbonate and carbonate ions are favoured over CO2, and can reach high concentrations because the ionic hydrated forms (bicarbonate and carbonate) are much more soluble in water than is CO2. Try an easy experiment to show this: dissolve a tablespoon of soda (sodium BICARBONATE) in water, split it into two glasses and let it sit overnight (more than enough time to reach equilibrium). Then put a few drops of drain cleaner or a lye pellet (strong bases - favours bicarbonate/carbonate) into one glass and a tablespoon of vinegar, lemon or lime juice (acidic - favours CO2) in the other glass. Nothing will happen to the strong base, as the favoured bicarbonate remains in that soluble form, while in the acid glass CO2 will be SPONTANEOUSLY formed from the large resevoir of dissolved bicarbonate, above its solubility maximum, and it will start bubbling out. No carbonic anhydrase there! I have removed the strikethrough.132.204.195.69
- The interconversion of CO2 and bicarbonate/carbonate is indeed spontaneous, and soda-pop goes flat because it reaches equilibrium. Pop is kept supersaturated with CO2 under pressure, when the pressure is removed, the supersaturated CO2 rapidly bubbles out (minutes to hours); this effervescence is delightful but unfortunately transient. When it is "flat" it is at equilibrium. The relative amounts of bicarbonate and CO2 in pop is not too important here, as pop is very acidic and bicarbonate (and carbonate) is practically absent.
- [2]: Irrelevant. Keep in mind that I'm aware of your findings, and I'm already treading on WP:NOR. Assume aqueous solution is pure, distilled water. No adulterants. Some acids _don't_ favour CO2: They make it more soluble. Phosphate is one, so you're off on two facts. 216.234.170.66 16:32, 3 August 2006 (UTC)
- Well, I am not sure what findings you think you are aware of Mr. Bond, but that is not me! If you are interested in my research, you can read up on it here. If you want some independent academic source for my contention that HCO3<->CO2 interconversion is spontaneous, but slow, I have included one [1] (of hundreds). I earlier thought I would spare the readers because I thought it was accepted enough just to state it. From Badger & Price: "Carbonic anhydrase is required in biological systems because the uncatalyzed interconversion between CO2 and HCO3- is slow when compared to the flux rates between these species, which may be required in living cells... The uncatalyzed first-order rate constant for the conversion of CO2 to HCO3- is about 0.05 per s at 25 °C and pH 8. Thus at present atmospheric CO2 levels (350 ppm, leading to a chloroplast [CO2] of about 8 uM) the uncatalyzed rate of interconversion of CO2 to HCO3- will be about 0.5 x 10-3 mM/s. This is about 10^4 times slower than the biological flux that takes place via CO2 fixation by the primary CO2-fixing enzyme, ribulose bisphosphate carboxylase/oxygenase (Rubisco)." Is that reference enough? I have removed the "needs citation" tag. 132.216.227.246 19:12, 31 August 2006 (UTC)
- Thanks for bothering to include this information and source about the biological flux rate, I will use it in my lectures!Kcsunshine999 (talk) 19:11, 6 October 2021 (UTC)
- Well, I am not sure what findings you think you are aware of Mr. Bond, but that is not me! If you are interested in my research, you can read up on it here. If you want some independent academic source for my contention that HCO3<->CO2 interconversion is spontaneous, but slow, I have included one [1] (of hundreds). I earlier thought I would spare the readers because I thought it was accepted enough just to state it. From Badger & Price: "Carbonic anhydrase is required in biological systems because the uncatalyzed interconversion between CO2 and HCO3- is slow when compared to the flux rates between these species, which may be required in living cells... The uncatalyzed first-order rate constant for the conversion of CO2 to HCO3- is about 0.05 per s at 25 °C and pH 8. Thus at present atmospheric CO2 levels (350 ppm, leading to a chloroplast [CO2] of about 8 uM) the uncatalyzed rate of interconversion of CO2 to HCO3- will be about 0.5 x 10-3 mM/s. This is about 10^4 times slower than the biological flux that takes place via CO2 fixation by the primary CO2-fixing enzyme, ribulose bisphosphate carboxylase/oxygenase (Rubisco)." Is that reference enough? I have removed the "needs citation" tag. 132.216.227.246 19:12, 31 August 2006 (UTC)
References
- ^ Badger MR, Price GD. 1994. The role of carbonic anhydrase in photosynthesis. Annu Rev Plant Physiol Plant Mol Biol. 45:369–392
Million or Billion Fold?
- [3]: Valid question for second [citation needed] inclusion considering that the article on carbonic_acid says billion. That's three decimal orders of magnitude! Let's see if I really care how to calculate the concentration of bicarbonate in water at 100kPa.
- Obviously, there is too much confusion about the million or billion thing. What does "increase by a million fold" actually mean? The rate of interconversion varies with pH, concentration of each carbon species, temperature, presence of other ions, etc. etc. etc. To try to make a more clear statement about the rate of the enzyme, I reported a range of representative catalytic rates for the forms of this enzyame and added a citation. I hope that is clear.132.216.227.246 19:52, 31 August 2006 (UTC)
Katz's Law: Men and wimin will act rationally when they've exhausted all other possible alternatives. 216.234.170.66 18:12, 3 August 2006 (UTC)
References
Picture with the coordinated metal ion
I do not think that the picture should be left in the article. The metal ion is coordinated and not actually bound. While this might be okay for the histidine groups, the hydroxide group should definitely not be connected with the ion. An alternative would be to use dashed lines to point out the nature of the coordination. —Preceding unsigned comment added by HerrMarder (talk • contribs) 14:19, 22 April 2008 (UTC)
Zinc and cadnium
What is special about zink and cadmium? These atoms are at the end of the first and second transition groups and have full d shells whose electrons have an energy just below that of the valence s electrons. In a compound the d electrons mix in to the bonds to some extent leaving a d type vacancy. The empty d orbital is long and thin with lobes sticking out of the atom in opposite directions and having the same sign of the wave function. This is similare to the wave function of the pi electrons on the liniar CO2 molecule which stick out on opposite sides of the central carbon atom with the same sign. Thus the CO2 molecule sticks to the Zn or Cd donating an electron to the d shell and leaving it positivly charged and with a vacancy so that it is easy for the negitively charged oxygen atom of H2O to react with it. 89.139.194.69 01:03, 23 November 2008 (UTC)
Mechanism of carbonic anhydrase
Farhanasadmohamed (talk) 00:08, 7 December 2015 (UTC)
References
- ^ Bertini, I. (2007). Biological inorganic chemistry (p. 180). Sausalito, Calif.: University Science Books.
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