TPR Bio Reaction Coupling Question

[bozins]

To explain reaction coupling and the use of ATP as an energy source the following equations are used

ATP --> ADP + PO4 G= -12 kcal/mol
A + PO4 --> APO4 G= +2 kcal/mol
APO4 + B --> C + PO4 G= +5 kcal/mol

Then it goes on to distinguish that enzymes have a kinetic role rather than a thermodynamic one, but then states that reaction coupling "allows enzymes to promote otherwise unfavorable reactions"

The last statement has caused me confusion. Is the PO4 in the above reaction sequence considered an enzyme?

Thanks guys!

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[dudewheresmymd]

To explain reaction coupling and the use of ATP as an energy source the following equations are used

ATP --> ADP + PO4 G= -12 kcal/mol
A + PO4 --> APO4 G= +2 kcal/mol
APO4 + B --> C + PO4 G= +5 kcal/mol

Then it goes on to distinguish that enzymes have a kinetic role rather than a thermodynamic one, but then states that reaction coupling "allows enzymes to promote otherwise unfavorable reactions"

The last statement has caused me confusion. Is the PO4 in the above reaction sequence considered an enzyme?

Thanks guys!

What page is this on? PO4 is an intermediate from steps 1 to 2 and from steps 2 to 3 it serves as a catalyst. So my hunch is that it is an enzyme since enzymes are catalysts, but need more background to be sure.

 

[bozins]

It's on page 23. It mentions that enzymes can appear to have a thermodynamic role when multiple reactions are coupled as they can affect favorability, which makes sense if PO4 is an enzyme but it seems kind of weird

 

[image187]

the enzyme completing the above reactions isn't mentioned. It's just saying you can have a couple of uphill reactions take place using the energy taken from breaking apart ATP