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welcome to this lecture on the electron
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transport chain a critical component of
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cellular respiration through this
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process cells harness energy to produce
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ATP the molecule that powers most
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biological functions let's break down
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the steps of the electron transport
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chain and see how electron transfer
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leads to ATP production the electron
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transport chain or Etc is located in the
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inner membrane of the mitochondria it
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consists of a series of protein
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complexes and molecules that transfer
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electrons from nadh and fadh2 to
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molecular oxygen generating a proton
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gradient that powers ATP synthesis let's
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examine this step by step nadh is
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generated in metabolic pathways such as
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the TCA cycle bay1 ta3 oxidation and the
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pyruvate dehydrogenase reaction inside
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the mitochondria nadh transfers its
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electrons to complex 1 or nadh
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dehydrogenase this complex contains a
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co-actor called fmn which accepts
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nadh fmn then transfers these electrons
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one at a time to ion sulfur centers
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within complex one the electrons are
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eventually passed to ubiquinone also
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known as Coq during this process Coq is
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reduced to ubiquinol the energy released
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here pumps protons from the
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mitochondrial Matrix into the
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intermembrane space establishing a
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proton gradient this gradient is a key
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driver for ATP synthesis later in the
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process next electrons are donated by
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fadh2 which is formed during the
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oxidation of succinate to fumerate in
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the TCA cycle these electrons are
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transferred to complex 2 also known as
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dehydrogenase unlike complex 1 complex 2
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does not contribute to the proton
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gradient as it does not pump protons
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across the membrane instead it directs
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electrons to ubiquinone which is then
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reduced to ubiquinol both nadh and fadh2
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electrons converge at this point
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continuing their Journey Through the ETC
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coq2 transfers its electrons to complex
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3 also known as cytochrome reductase
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within this complex electrons move
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through a series of carriers including
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cytochrome B and cytochrome C1 before
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reaching cytochrome C during this
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process ion within cytochrome alternates
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between its fe3 EA A1 and fe2 ea1 States
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as it accept Cs and donates electrons
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the energy released here pumps
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additional protons into the
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intermembrane space further
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strengthening the proton gradient for
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every molecule of nadh oxidized two
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cytochrome c molecules are reduced
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ensuring efficient electron transfer in
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the final step electrons from cytochrome
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C are transferred to complex 4 also
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known as cytochrome oxidase this complex
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catalyzes the reduction of molecular
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oxygen to water for each pair of
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electrons one oxygen molecule is reduced
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to form water as electrons move through
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complex 4 additional protons are pumped
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into the intermembrane space further
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amplifying the gradient the proton
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gradient established across the inner
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mitochondrial membrane serves as the
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driving force for ATP synthesis protons
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flow back into the Matrix through ATP
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synthes a protein complex that converts
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this flow into mechanical energy to
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synthesize ATP from ADP and inorganic
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phosphate to summarize the electron
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transport chain uses electrons from nadh
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fadh2 to create a proton gradient this
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gradient Powers ATP synthesis completing
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the process of oxidative phosphorilation
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each step from electron trans transfer
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to proton pumping is essential for the
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efficient production of cellular energy
