Berkeley Review Biology Chapter #1

[Happy_Puppy5000]

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Hello All:

Could someone please walk me through Berkeley Review Biology Chapter #1 passage IV, specifically question 22, 24, 25 and 26. I am a bit confuse even after reading the answer explanations. Thanks.

 

[Anion]

Picture of question?

 

[Happy_Puppy5000]

Hopefully this is not considered copyright violation. If it is, moderator please remove.

 

[deleted966164]

26. I’d say answer A. That nitrogen on the right side of the figure would most likely be protonated in acidic conditions of the stomach thus the molecule ceases to be basic. The passage states that decrease of the amount of base facilitates the removal of anesthetics and results in a shorter duration of the effects.

 

[deleted966164]

In acidosis, I’d assume that the same nitrogen gets protonated. The group on the right of the molecule becomes positively charged and thus more water soluable. The substance may cross barriers more freely weakening the effect of anesthesia. Answer C.

 

[deleted966164]

For 24. Lidocaine has pKa of 7.6-7.8, Procaine 8.1-8.6. Thus Procaine is a stronger base.

The pH in tissue is somewhere around 7.4. In those conditions, more of the Lidocaine will exist in unprotonated form this doing its anesthesia job rather than Procaine. I’d go with answer A.