In this image, the mitochondrial matrix is seen above and the intermembrane space is found below the inner mitochondrial membrane. Proteins in the inner mitochondrial membrane involved in the electron transport chain: Complex I (I), Complex II (II), Complex III (III), Complex IV (IV), ubiquinone (Q), cytochrome c (Cyt C) and ATP synthase. This process generates an electrochemical gradient that couples the oxidative reactions with the phosphorylation of ADP producing ATP in a process called oxidative phosphorylation.įigure 1. The electron transport chain consists of a series of redox reactions that transfer electrons from NADH and FADH 2 nicotine adenine dinucleotide N A D H, and flavin adenine dinucleotide F A D H two through various intermediates to the final electron acceptor, oxygen (see detailed ETC steps). The proteins involved in the electron transport chain are outlined in Figure 1. Oxidative phosphorylation: The final stage of cellular respiration where the combined action of the electron transport chain and chemiosmotic coupling result in ATP production.Įlectron transport chain: a series of proteins embedded in the inner mitochondrial membrane that takes up highly energetic electrons from NADH and FADH 2 and uses the energy to form proton gradient across the membrane.Ĭhemiosmotic coupling: A process in which the movement of protons across the mitochondrial membrane downward their gradient is coupled to ATP production via phosphorylation of ADP.The electron transport chain takes place in the inner mitochondrial membrane and is the final step of aerobic cellular respiration. As hydrogen ions flow down their gradient and back into the matrix, they pass through an enzyme called ATP synthase, which harnesses the flow of protons to synthesize ATP.At the end of the electron transport chain, electrons are transferred to molecular oxygen, which splits in half and takes up hydrogen ions to form water.This pumping establishes an electrochemical gradient. Some of the energy is used to pump hydrogen ions, moving them out of the mitochondrial matrix and into the intermembrane space. As electrons are passed down the electron transport chain, they move from a higher to a lower energy level, releasing energy.In the process, they turn back into NAD+ and FAD, which can be reused in other steps of cellular respiration. It is the stage that produces the most ATP molecules. NADH: Molecule that acts as an electron carrier in cellular respiration. Reduced electron carriers (NADH and FADH 2) from other steps of cellular respiration transfer their electrons to molecules near the beginning of the electron transport chain. The electron transport chain is the last stage of the respiration pathway. Krebs Cycle: Second stage of aerobic respiration in which two pyruvate (pyruvic acid) molecules from the first stage react to form ATP, NADH, and FADH.Section Bank B/B Section Passage 12 Question 95 1 Passage 13 Question 85īiology Question Pack, Vol 2. In this process, protons flow down their concentration gradient into the matrix through the membrane protein ATP synthase, causing it to spin (like a water wheel) and catalyze conversion of ADP to ATP. Take a look at the diagram below which summarizes oxidative phosphorylation.īiology Question Pack, Vol. This gradient is used by chemiosmotic coupling to make ATP through phosphorylation of ADP. proton gradient) forms across the inner membrane of mitochondria. As a result, the electrochemical gradient (i.e. The energetically “downhill” movement of electrons through the chain causes pumping of protons into the intermembrane space by the first, third, and fourth complexes. In the electron transport chain, electrons are passed from one molecule to another as a series of redox reactions. In the mitochondrial matrix, the electron carriers NADH and FADH 2 deposit the electrons they gained from glycolysis and the citric acid cycle in the electron transport chain – a series of proteins embedded in the inner mitochondrial membrane. Take a look at the diagram below that shows the interconnectedness between cellular energy pathways. Actually, most of the ATP production during cellular respiration happens here. (C) The electron transport chain is located in the cytoplasm. Energy stored in these molecules is converted into cellular energy currency (i.e. aerobic respiration is produced by substrate level phosphorylation. Highly energetic electrons that are extracted during the decomposition of food molecules by cellular metabolic pathways are stored in electron carriers – NADH and FADH 2. Oxidative phosphorylation, incorporating two interdependent processes – the flow of electrons through electron transport chain down to the oxygen and chemiosmotic coupling -, is the final stage of cellular respiration.
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