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Title: What is responsible for converting H2CO3 to HCO3- and H+ in response to .... Post by: NeedsAPbiohelp on May 6, 2011 This question is about the bicarbonate buffering system in pH. What is responsible for dissociation of carbonic acid (H2CO3) to HCO3- and H+ in response to rise in pH levels? I understand how HCO3- and H+ can react together again to form carbonic acid (H2CO3) but how exactly does carbonic acid (H2CO3) separate into a bicarbonate ion (HCO3-) and H+? Does it just spontaneously happen? I have no idea what I was rambling on about before :-:) I haven't gotten much sleep lately due to the amount of preparation I have put into the AP Bio test May 9th.
Title: Re: What is responsible for converting H2CO3 to HCO3- and H+ in response to .... Post by: duddy on May 7, 2011 Quote Does it just spontaneously happen? Enzymes cause this conversion (carbonic anhydrase). For example, when excess hydrogen ions are added to the system the equilibrium is shifted to the left. This means that some of the added hydrogen ions will react with the bicarbonate ions to produce carbonic acid and the carbonic acid will dissociate into carbon dioxide and water as shown below. (http://academic.brooklyn.cuny.edu/biology/bio4fv/page/image27.gif) When hydrogen ions are removed from the reaction, the equilibrium will shift to the right. More carbon dioxide will combine with water and more carbonic acid will be produced and more hydrogen ions and bicarbonate ions will be produced. (http://academic.brooklyn.cuny.edu/biology/bio4fv/page/image28.gif) Title: Re: What is responsible for converting H2CO3 to HCO3- and H+ in response to .... Post by: NeedsAPbiohelp on May 7, 2011 Thanks for your post duddy! But i'm still slightly confused. Let me clarify. I understand Carbonic anhydrase synthesizes CO2 and H2O to create carbonic acid. But by what mechanism does the carbonic acid dissociate? Do hydroxide ions play any kind of role in causing Carbonic acid to dissociate?
Title: Re: What is responsible for converting H2CO3 to HCO3- and H+ in response to .... Post by: duddy on May 7, 2011 Once it's generate, it's released because its structure no longer fits in the enzymes reaction site; this allows it to dissociate.
Title: Re: What is responsible for converting H2CO3 to HCO3- and H+ in response to .... Post by: padre on May 7, 2011 Hi, I found this in my only eBook:
(http://canmedia.mcgrawhill.ca/istudy3/books/0070741751/images/figures/bro41751_eq4601.jpg) About two-thirds of the carbon dioxide produced during metabolism is converted into a less toxic and more soluble form: bicarbonate ions. In the process, hydrogen ions are formed according to the following reaction, where H2CO3 is a short-lived compound called carbonic acid that immediately dissociates to a hydrogen ion and a bicarbonate ion: The left side of this reaction is readily reversible and is catalyzed in both directions by the enzyme carbonic anhydrase, which is present in high amounts in red blood cells. If CO2 levels increase, the reactions move from left to right. Conversely, if the concentration of hydrogen ions rises or the levels of CO2 decrease, the reactions move from right to left. In body tissues, CO2 levels are high because metabolism is generating the gas. Thus, the reactions move to the right, and CO2 is converted to H+ and (HCO3?). As blood flows through the lungs, however, dissolved CO2 diffuses into the alveoli and is exhaled. Thus, CO2 levels in the lung capillaries decrease, which makes the reactions proceed in the opposite direction, right to left so that (HCO3?) is converted back to CO2 and exhaled. |