Lesson 5 -Electron Transport Chain

Oxidative Phosphorylation Remember, ATP is the universal energy currency of the cell. NADH and FADH 2 reducing power is utilized to produce more ATP through a process called oxidative phosphorylation which utilizes an Electron Transport Chain.

Electron Transport Chain The electron transport chain of the mitochondrion is embedded in the folded inner membrane (cristae). It consists of multiple protein complexes with increasing oxidizing power (better electron acceptors). Oxygen acts as the final electron acceptor, and is converted to H 2 O in the process

Details of ETC NADH donates two electrons to complex 1, the electrons move through the chain with Hydrogen being pumped at complex 1, complex 3, and complex 4. FADH 2 donates two electrons to complex 2, with Hydrogen being pumped at complex 3, and complex 4. Oxygen acts as the terminal electron acceptor, producing H 2 O. FADH 2 is at a lower energy state than NADH, and thus has less reducing power. It enters at a later stage in the chain which results in fewer Hydrogen ions being pumped.

Proton Motive Force Like we will see in the thylakoids of chloroplasts, ATP synthase utilizes the Hydrogen Ion gradient to drive ATP synthesis. As Oxygen is responsible for helping drive the building of this gradient, we call this type of ATP production Oxidative Phosphorylation.

Theoretical Yield A total theoretical yield of 36 (Eukaryotes) or 38 (Prokaryotes) results from a single glucose molecule Why do you suppose there is a difference?

Experimental Yield Experimentally, we only see about 30 ATP produced in Eukaryotic aerobic respiration. Possible explanations: some H + leaks through membrane ADP and Pyruvate are actively transported into the mitochondria

Feedback Inhibition Response Cells control the rate at which ATP is generated via feedback inhibition and other types of regulation. Phosphofructokinase in glycolysis can be allosterically inhibited by excess ATP, and activated by ADP. Pyruvate dehydrogenase can be inhibited by excess NADH. Under the right conditions, ATP synthase can even function in reverse, hydrolyzing ATP to maintain proper H + concentrations.

Review 1)As a result of glycolysis, pyruvate oxidation, and the Kreb’s cycle, only a small portion of the energy of glucose has been converted to ATP. In what form is the rest of the usable energy found at this stage? 2)How many Acetyl-CoA molecules are produced from one glucose molecule during aerobic respiration? 3)True or false Pyruvate is a three carbon compound that is converted into acetyl-CoA in the mitochondrial matrix before entering the Kreb’s cycle Glucose requires two molecules of ADP to be activated in glycolysis

4)Watch 5)Compare substrate level phosphorylation and oxidative phosphorylationWatch 6)Describe the function of NAD+ and FAD in cellular respiration 7)What are the final products of aerobic cellular respiration? 8)Why is aerobic respiration a more efficient energy-extracting process than glycolysis alone? 9)What part of a glucose molecule provides electrons in cellular respiration? 10)Distinguish between an electron carrier and a terminal electron acceptor.