Lesson 4/Biochem C.1

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Lesson 4/Biochem C.1

Post by dtufano » Fri Nov 30, 2018 7:41 pm

Hello! I have a question from Lesson 4, part 4, slide 1. Towards the end of the slide, Clara explains that steps 1, 3, and 10 are highly exergonic, spontaneous reactions. This seems to make sense and clearly explains why the reverse reaction is basically impossible. However, in the Biochemistry Book, Chapter 1, it states that steps 1 and 3 involve the highly unfavorable, endergonic reaction. It does follow with the fact that these steps are coupled to highly favorable reaction of ATP >> ADP (does this make the "net" reaction exergonic?) I am now a little confused on this topic and whether or not steps 1 and 3 are considered exergonic or endergonic. Thank you in advance for the clarification!

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Re: Lesson 4/Biochem C.1

Post by NS_Tutor_Will » Mon Dec 03, 2018 8:54 am

Hi Danielle,

You could think of one component of the reaction being exergonic and another being endergonic. Getting a phosphate group onto a carbohydrate is unfavorable (endergonic), but removing that same phosphate from ATP is favorable (exergonic). The net of both reactions is favorable, but just putting a phosphate onto a carbohydrate would be highly unfavorable. So, depending on your perspective, both could be true!

I hope this helps!
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