Princeton review hyperlearning science workbook

[crestfall]

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This is a question from passage 22. This book is from the 2008 class. It is copyrighted 2005.

Adenylate cyclase stimulation takes place after receptors bind hormone because:

a) of the exchange of GTP for GDP bound to the G-s-alpha complex.

b) of the exchange of GDP for GTP bound to the G-s-alpha complex.

c & d are wrong.

The solution claims (a) is correct. I think its (b)

any thoughts? Isnt GDP switched with GTP because it is active with GTP not GDP. The picture supports this and so does the passage as well as my physiology textbook. Am I interpeting this answer chioce incorrectly? is the book wrong?

thanks in advance

 

[Doodl3s]

yea, just reading that I had to re-read it a few times. G-proteins hydrolyze the GTP to GDP to stop working. So you'd never replace a GTP with a GDP... since GTP gets hydrolyzed to GDP THEN switched out for a GTP which is answer A

it says exchange of GTP for GDP BOUND TO complex... meaning the GDP is bound and then switched out. you're last explanation is correct... you're just misreading the answers.

 

[crestfall]

ooohhh-kay

It makes sense when you say that you would never replace a GDP with a GTP because GTP get hydrolyzed to a GDP. The inactive form releases a GDP and binds a GTP and is then active.

wait... i just scrolled down and re-read what you said.

Wow. Okay i was reading it wrong. So answer (A) does describe GTP bound to the alpha subunit being the active form. wow

I was reading it wrong. thanks alot for the feedback. I guess im just starting to get burned out a little bit.

Thank you Thank you. .... sighs..

 

[hqt331]

Um, is it bad that I have no idea what adenylate cyclase stimulation is???

 

[CaliforniaKid]

Um, is it bad that I have no idea what adenylate cyclase stimulation is???

I would say that it is very bad. This lack of knowledge will certainly drop your bio score 2-3 points.

 

[matth87]

Um, is it bad that I have no idea what adenylate cyclase stimulation is???

Go look up peptide hormones and their effects on plasma membrane receptors. See how they turn on adenylate cyclase.

 

[Will Hunting]

This is a question from passage 22. This book is from the 2008 class. It is copyrighted 2005.

Adenylate cyclase stimulation takes place after receptors bind hormone because:

a) of the exchange of GTP for GDP bound to the G-s-alpha complex.

b) of the exchange of GDP for GTP bound to the G-s-alpha complex.

c & d are wrong.

The solution claims (a) is correct. I think its (b)

any thoughts? Isnt GDP switched with GTP because it is active with GTP not GDP. The picture supports this and so does the passage as well as my physiology textbook. Am I interpeting this answer chioce incorrectly? is the book wrong?

thanks in advance

Don't use outside knowledge. If you were active, in the early description it states that GTP is exchanged for bound GDP alpha. When in doubt, go back to the passage. Your outside knowledge is so you can better understand the passage. Once you do this, you'll kill the biology questions. Always relate to passage. Treat the BS like a mini verbal.