Go Back   Science Forums Biology Forum Molecular Biology Forum Physics Chemistry Forum > General Science Forums > Biochemistry Forum
Register Search Today's Posts Mark Forums Read

Biochemistry Forum Discuss and post questions regarding the study of Biochemistry. If you need homework help this is the place to ask!


Thermodynamics: Calculating equilibrium constants?

Thermodynamics: Calculating equilibrium constants? - Biochemistry Forum

Thermodynamics: Calculating equilibrium constants? - Discuss and post questions regarding the study of Biochemistry. If you need homework help this is the place to ask!


Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 10-25-2010, 04:54 PM
Pipette Filler
Points: 4, Level: 1 Points: 4, Level: 1 Points: 4, Level: 1
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Oct 2010
Posts: 1
Thanks: 0
Thanked 0 Times in 0 Posts
Default Thermodynamics: Calculating equilibrium constants?



Hey all, I am currently studying Marine Biology and have recently started an optional biochemical statistics module, in the hope that it would give me better insight into statistical analysis. Unfortunatley I didn't expenct to be handed a Thermodynamics worksheet on the first lecture! I've been working through the worksheet but I can't understand how to go about solving the question below. Any help will be much appreciated.


5) The following two transformations occur in glycolysis:

gloucose + Pi ---> gloucose-6-P + H20 ( ∆D = +17.1 kL/mol)
PEP + H20 ---> pyruvate + Pi ( ∆D = -55.2 kL/mol)

In glycolysis, both reactions are coupled to either ATP snthesis or hydrolysis:

ATP + H20 ---> ADP + Pi ( ∆D = -30.5 kJ/mol)

Write down reactions for the coupled reactions and calculate their equilibrium constants at 298 K.
Reply With Quote
  #2  
Old 10-29-2010, 12:32 PM
Pipette Filler
Points: 563, Level: 11 Points: 563, Level: 11 Points: 563, Level: 11
Activity: 0% Activity: 0% Activity: 0%
 
Join Date: Apr 2010
Posts: 18
Thanks: 0
Thanked 2 Times in 2 Posts
Default Re: Thermodynamics: Calculating equilibrium constants?

The first reaction is ATP + glucose --> glucose-6-Pi + ADP. The deltaG (I assume your deltaD is in fact deltaG?) for this reaction would be -13.5 kJ/mol (again, I assume your notation was a mistake? kilolitres per mole would be unusual to say the least...). This was simply calculated as the sum of the deltaGs of the two reactions, as they both proceed in the same direction. Now you use the formula deltaG = RTlnK to calculate the equilibrium constants. R is the gas constant, T is absolute temperature and lnK is the natural logarithm of the equilibrium constant.
Use the same process for the other reaction, but note that here you are producing ATP from PEP and ADP. The deltaG is therefore -24.7 kJ/mol. You sum up -55.2 kJ/mol for the PEP reaction and +30.5 kJ/mol for the ATP reaction, because you are going in the reverse direction. Hope this helps.
Reply With Quote
Reply

Tags
calculating , constants , equilibrium , thermodynamics


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
TCA Thermodynamics: calculating ΔG Becky_A Biochemistry Forum 0 02-22-2009 03:14 PM
Elementary thermodynamics question Boo Physics Forum 1 05-06-2006 04:31 PM
Thermodynamics - statement of the obvious? tadchem Physics Forum 17 02-15-2006 11:14 PM
fundamental physical constants brian a m stuckless Physics Forum 0 10-09-2005 08:56 AM


All times are GMT. The time now is 08:50 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 - 2012 Molecular Station | All Rights Reserved
Page generated in 0.12658 seconds with 16 queries