(Glycolysis) - quick TBR passage question

[yestomeds]

Hey this is from the old TBR "metabolic pathways" passage #1 (p. 229, answers on p. 257). This should be book II.

Question 4. You have this drug/poison thing that ultimately makes glycolysis make 2 ATPs only, thus 2 in and 2 out means no net ATP. I get that.
So why in the answers section did TBR say "All of the free energy difference b/w glucose and pyruvate will be lost as heat?" (very bottom of p.257 in the answers section).

What free energy difference? 2 ATP in and 2 out, so...? Thanks y'all.

---

Members don't see this ad.

 

[sc4s2cg]

Remember that ATP is not the only byproduct of glycolysis. There is also NADH, pyruvate, and water. If I understand correctly, the TBR quote is saying that if you take the deltaG of the reaction, you will still have a couple Jules leftover that is not accounted for just by the physical byproducts. That left over Jule is emitted in the form of heat.

Overall equation: Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O

 

[amy_k]

Basically there is a negative delta G for the overall reaction of glycolysis (bottom line, breaking up glucose, C6 to pyruvate, 2xC3 releases energy). The delta G for glycolysis is -196kJ/mol which is the driving force for the reaction. ATP acts as a "store" of this free energy, we also learn that some of this free energy is lost as heat energy along the way. If there is no net ATP production then all the 196kJ/mol is lost as heat rather than approx. 60 kJ/mol being stored into two ATP molecules.

 

[yestomeds]

THANK YOU!!

 

[BerkReviewTeach]

Nice explanations!