1. The electron transport chain is a great example of energy transformation. Exp
ID: 3507851 • Letter: 1
Question
1. The electron transport chain is a great example of energy transformation. Explain where two of these transformations are occurring and how this is advantageous for the production of ATP.
2. Why do the electrons carried by NADH + H+ yield a greater number of ATP molecules than those electrons carried by FADH2?
3. What is proton motive force? How is it related to ATP production?
4. How does oxidative phosphorylation differ from substrate-level phosphorylation? Explain and use an example.
5. Why do electrons only move in one direction in the electron transport chain? What is the final electron acceptor? Why?
Explanation / Answer
1. It takes place at the inner mitochondrial membrane
2 NADH + H+ produces 3 ATP during the ETC (Electron Transport Chain) with oxidative phosphorylation because NADH gives up its electron to Complex I, which is at a higher energy level than the other Complexes. When Complex I transfers the electron to Complex III, energy is given off to pump protons across the membrane, creating a gradient. The electron moves again to Complex IV and again pumps more electrons across the membrane. Because NADH started with Complex I, it had more chances to pumps more protons across the gradient, which powers the ATP synthase and gives us 3 ATP per molecule of NADH. FADH2 produces 2 ATP during the ETC because it gives up its electron to Complex II, bypassing Complex I. By bypassing Complex I, we missed a chance to pump protons across the membrane, so less protons have been pumped by the time we get to Complex IV. Protons still have been pumped, enough to fuel 2 ATP created by ATP synthase.
3. Proton motive force (PMF) is the force that promotes movement of protons across membranes downhill the electrochemical potential.
the pmf drives the ATP synthase (complex V), a proton turbine converting the proton gradient into chemical energy in the form of ATP .
4. Substrate-level phosphorylation is directly phosphorylating ADP with a phosphate and energy provided from a coupled reaction. Substrate level phosphorylation will only occur if there is a reaction that releases sufficient energy to allow the direct phosphorylation of ADP. Oxidative phosphorylation is when ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons. That process generates an electrochemical gradient, which is required to power the ATP synthase.
5. Electrons move from a reduced donor such as malate to an oxidised receptor such as oxaloacetic acid down the favorable energy gradient.
The last electron acceptor is O2 (oxygen). Beacuse electron move towards favourable energy gradient due to the fact that they move towards more positive reduction potential and oxygen has it and thus electron has a greater affinity for oxygen
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