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hercola t1_j15d1o2 wrote

Reply to comment by piranhabait89 in How does pyruvate know to go to the mitochondria or to do the anaerobic reaction? by WeedCat1

Substrates flow down their concentration gradients the same way that if you pour concentrated syrup into water, it will naturally spread all throughout. The reason why it does this is that it is thermodynamically favorable to equilibrate like this.

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user280102 t1_j15vf55 wrote

This makes sense but my question is that the molecules outside the mitochondria don't "know" that the concentration within the matrix is lower. Is it that the receptor is sensitive to concentration of pyruvate within the matrix, so that its activity depends on the intra-mitochondrial concentration?

Thinking out loud here but could it be that the affinity of the receptor depends on the extra-mitochondrial matrix regardless of within? Maybe affinity is the wrong word too, more like the increased probability of pyruvate binding to the receptor the higher the concentration.

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hercola t1_j15w9bn wrote

Nothing has to know about the concentration gradient. As long as there is a way to flow, substrates will spontaneously flow.

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The_RealKeyserSoze t1_j16b7sf wrote

>“This makes sense but my question is that the molecules outside the mitochondria don't "know" that the concentration within the matrix is lower.”

They don’t need to “know”. They are randomly bouncing around, if there are more bouncing around on one side of a wall odds are more will pass through the gate to the side with less bouncing around than the other way around. And so they flow with the concentration gradient.

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