--- title: "Redox Potentials and the Proton-Motive Force" description: "Electrons pass down a chain of carriers arranged in order of their standard potentials, and the energy released at three points is used to move protons out. The gradient stores that energy as both a c" canonical: https://lightmysky.com/learn/science/redox-potentials-and-the-proton-motive-force-mt_lU8kgepFRN source: https://lightmysky.com/learn/science/redox-potentials-and-the-proton-motive-force-mt_lU8kgepFRN.md retrieved: 2026-09-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Redox Potentials and the Proton-Motive Force Electrons pass down a chain of carriers arranged in order of their standard potentials, and the energy released at three points is used to move protons out. The gradient stores that energy as both a concentration difference and a voltage. Subject: Science · Area: Biochemistry & Molecular Biology · Ages 20 to 21 Page: https://lightmysky.com/learn/science/redox-potentials-and-the-proton-motive-force-mt_lU8kgepFRN ## Ready when they can - Orders carriers by potential and calculates the energy available for a stated electron transfer. - Separates the two components of the proton-motive force and says which dominates in mitochondria. - Predicts what an uncoupler does to electron flow and to ATP production. ## Lesson: Falling electrons, pumped protons The electron transport chain passes electrons down carriers ordered by increasing reduction potential, from NADH through complexes to oxygen. Each downhill transfer releases energy that pumps protons across the inner mitochondrial membrane, and the resulting gradient stores energy as the proton-motive force. Oxygen sits at the bottom as the final acceptor, which is why respiration stops without it. **Example.** You can price any step with the Faraday constant, 96.5 kJ per volt per mole. Moving 2 electrons across 0.2 volts releases 2 times 96.5 times 0.2, which is 38.6 kJ per mole. A bigger potential drop buys more pumping energy, which is why carrier order sets the energy budget of the chain. The proton-motive force has two components: a pH difference and a membrane voltage, and in mitochondria the voltage dominates. Pumped protons gather in the intermembrane space, leaving the matrix negative and alkaline, and both components push protons back inward through ATP synthase. Uncouplers let protons leak back past the synthase, so electron flow speeds up while ATP production collapses, which proves the gradient is the true intermediate. **Tip.** Check direction first in every question: electrons fall from low to high potential and end at oxygen. Redox bookkeeping stays simple if you remember that the donor is oxidized, the acceptor is reduced, and NADH becomes NAD plus when it donates. **Recap.** Electrons fall down ordered carriers toward oxygen, and the released energy is stored as a proton gradient with voltage and pH parts. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Oxidative Phosphorylation and Chemiosmosis](https://lightmysky.com/learn/science/oxidative-phosphorylation-and-chemiosmosis-mt_1wP3-14Y4V) - [The Citric Acid Cycle as a Hub, and Refilling It](https://lightmysky.com/learn/science/the-citric-acid-cycle-as-a-hub-and-refilling-it-mt_BPPfI-vnab) - [Standard Electrode Potentials and Predicting Redox Reactions](https://lightmysky.com/learn/science/standard-electrode-potentials-and-predicting-redox-reactions-mt_LDI10CjoAI) ## Opens up - [ATP Synthase as a Rotary Machine](https://lightmysky.com/learn/science/atp-synthase-as-a-rotary-machine-mt_PDe3f-FVfD)