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h99h20baby
Joined: 01 Jul 2007
Posts: 40
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 Posted: Mon Jul 30, 2007 6:08 pm Post subject: Question 6 |
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I realize that when one O2 binds to Hb it facilitates the binding of another O2 and so on. I knew that from outside info and I couldn't really locate the info inside the passage. The answer said that it could be deduced from the passage. Likewise, I was not sure exactly why Hb had less affinity for O2 than myoglobin. Is that because on the graph there was a quick and very steep curve for the saturation percent for myoglobin but a sigmoidal curve for Hb?? What does the sigmoidal graph represent?
Thank you and sorry for all the questions! |
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admin
Site Admin
Joined: 08 Dec 2003
Posts: 2176
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| Posted: Mon Jul 30, 2007 9:40 pm Post subject: |
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| Quote: | | I realize that when one O2 binds to Hb it facilitates the binding of another O2 and so on. I knew that from outside info and I couldn't really locate the info inside the passage. The answer said that it could be deduced from the passage . . . . What does the sigmoidal graph represent? |
There are 2 clues: the passage mentions the cooperative binding in Hb with respect to allosteric interaction with other chemicals but not mentioning O2. But we know at least that Hb can perform cooperative binding.
The sigmoidal curve suggests that to get complete O2 saturation of Hb, it must occur in stages. This is consistent with the idea of cooperative binding.
| Quote: | | Likewise, I was not sure exactly why Hb had less affinity for O2 than myoglobin. Is that because on the graph there was a quick and very steep curve for the saturation percent for myoglobin but a sigmoidal curve for Hb?? |
Yes. For example, at 10 torrs, myoglobin is already 100% saturated while Hb is less than 10% saturated. Clearly myoglobin has a much greater affinity of O2. |
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msamadia
Joined: 02 Aug 2006
Posts: 13
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| Posted: Thu Aug 13, 2009 7:39 pm Post subject: |
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How come myoglobin and hemoglobin is not dependent on pH, is myogloin pH independent?
I chose that based on enzymes changing optimal activity under different conditions (pH).
Thank you. |
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jellywing_2058
Joined: 04 May 2009
Posts: 179
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| Posted: Fri Aug 14, 2009 7:32 am Post subject: |
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The question asks | Quote: | | 6) Which of the following can properly be inferred from the passage? |
III. The affinity of myoglobin and hemoglobin for oxygen is dependent on the pH of the environment.
According to the passage, this third statement is wrong because myoglobin is not pH dependent; only hemoglobin is, as shown in paragraph 3.
| Quote: | | Finally, myoglobin shows no change in oxygen binding over a broad range of pH, nor does CO2 have a noticeable effect on it. While with hemoglobin, the acidity enhances the release of oxygen. |
Do not complicate things, this question is very staightforward. |
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