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How do cells switch between full glucose oxidation and partial breakdown without oxygen?

Submitted by anonymous » Thu 05-Feb-2026, 01:13

Subject Area: General

2 member ratings

Hey everyone, so I've been thinking about this a lot lately after that brutal hike last weekend where I pushed way too hard up the last hill. My legs were burning like crazy, and I could literally feel them switching to some kind of backup mode just to keep moving. It got me wondering—how exactly do cells flip between doing the full-on glucose oxidation thing when there's plenty of oxygen around versus just partially breaking it down without any O2? Like, what triggers that shift so they don't completely stall out? Anyone got a simple way to picture it? I always thought it was just "no oxygen = fermentation," but it feels more nuanced than that in real life situations.

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RE: How do cells switch between full glucose oxidation and partial breakdown without oxygen?

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By anonymous » Thu 05-Feb-2026, 01:34, My rating: ✭ ✭ ✭ ✭ ✭

Man, that hike story hits home—I've had those moments too where everything feels heavy and slow. From what I've pieced together over time messing around with bio stuff for fun, the switch mostly comes down to oxygen availability shutting things off or on at the mitochondrial level. When O2 is there, the whole chain runs smoothly, pulling electrons through and cranking out tons of ATP from full breakdown. No oxygen means the electron transport grinds to a halt because nothing's accepting those electrons at the end, so NADH piles up and the cell has to regenerate NAD+ another way to keep glycolysis chugging along. That's when it leans into partial paths like lactic acid in muscles or ethanol in yeast. Super inefficient energy-wise, but it buys time. Oh, and if you're trying to wrap your head around the whole pathway visually, I stumbled on this cellular respiration chart a while back that lays it out nicely without being overwhelming—helped me connect the dots better. Just my two cents, though; it's not like I'm an expert or anything.

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