4
$\begingroup$

In order to initiate glycolysis, 2 ATP are necessary. In the glycolytic process, you generate an additional 4 ATP, which results in a net gain of 2 ATP.

If you don't undergo glycolysis, however, then you have an extra 2 ATP not being used. If you do glycolysis, you still got only 2 ATP. Am I missing something here?

Improve this question
$\endgroup$
3
  • 3
    $\begingroup$ replace "ATP" with "money" and you have a financial system - they do plenty well :) $\endgroup$
    – shigeta
    Mar 2, 2014 at 13:24
  • 1
    $\begingroup$ Turning 2 ATP into 4 ATP isn't good? $\endgroup$
    – mgkrebbs
    Mar 2, 2014 at 21:48
  • $\begingroup$ you said that glycolysis generates net 2 ATP. That means 2 ATP in excess of what you started with. Plus @Chinmay and Satwik's answers $\endgroup$
    – A. Kennard
    Mar 3, 2014 at 9:48

2 Answers 2

Reset to default
4
$\begingroup$

Remember that glycolysis yields 2 NADH as well as 2 net ATP. This NADH can be used to a terminal electron acceptor to produce an end product with a net gain of ATP. End-products of fermentation can include lactate, acetate, butyrate, propionate and ethanol, all of which generate different amounts of additional ATP.

The exact pathways involved vary according to the organism, but anywhere between 1 (or even 0.5) and 4 additional ATPs can be generated, even without the involvement of oxygen. In the case of aerobic respiration of course, the NADH feeds into the electron transport chain and yields ATP.

EDIT: It's perhaps worth noting that the 2 ATP is gained. See @SatwikPasani's answer for the math.

Improve this answer
$\endgroup$
0
3
$\begingroup$

Suppose the cellular pool has $x$ATP before starting glycolysis. In the initial phosphorylation steps, we use up two ATP to get the total tally at $(x-2)$ATP. The following steps yields $4$ ATP which brings the final total to $(x+2)$ATP.
Assuming the cell is performing fermentation, the two additional $NADH$ formed will not be contributing to any ATP gain. And hence we earn a total of $2$ ATP in excess of the already existing amount.

Improve this answer
$\endgroup$
2
  • $\begingroup$ Actually, the NADH contributes to ATP gain in many fermentative systems. $\endgroup$
    – Chinmay Kanchi
    Mar 2, 2014 at 3:19
  • $\begingroup$ @ChinmayKanchi You might be correct. But I guess the OP's concern is limited to cases where substrate base phosphorylation is the only source of ATP. $\endgroup$
    – stochastic13
    Mar 2, 2014 at 12:04

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .