Hey everyone, I've been trying to wrap my head around this whole cellular respiration thing lately because I was reading up on mitochondria for a bio project and got stuck. Like, back in college I remember cramming for exams and just memorizing that NADH drops off electrons somewhere, but how does it actually shuttle that energy along the respiratory chain? Does it hand off the electrons step by step to those protein complexes in the inner membrane, or is there more to it with the proton gradient building up? Feels like the real action happens in those tiny mitochondrial folds, but I always pictured it as some sort of conveyor belt for energy packets. Anyone got a clearer way to think about it? It's been bugging me for days now.
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Yeah, that conveyor belt analogy isn't too far off actually. From what I've pieced together over time, those electron carriers like NADH basically pick up high-energy electrons during earlier steps (think Krebs cycle mostly), then they head to the inner mitochondrial membrane. NADH donates its electrons right to the first complex in the chain, getting oxidized back to NAD+ so it can be reused. The electrons then bounce through the chain—complex I to ubiquinone, then to III, cytochrome c, IV—and each jump releases a bit of energy that pumps protons out into the intermembrane space. That builds the gradient, and boom, ATP synthase uses the proton flow to make ATP. FADH2 skips the first complex and enters later, so it yields less ATP. I always found it helpful to glance at a cellular respiration chart when the steps start blurring together. Makes the whole flow feel less abstract, you know? Still blows my mind how efficient it all is compared to just burning sugar outright.