Lesson 5 -Electron Transport Chain

Oxidative PhosphorylationRemember, ATP is the universal energy currency of the cell. NADH and FADH2 reducing power is utilized to produce more ATP through a process called oxidative phosphorylation which utilizes an Electron Transport Chain.

Electron Transport ChainThe 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 H2O in the process

Details of ETCNADH donates two electrons to complex 1, the electrons move through the chain with Hydrogen being pumped at complex 1, complex 3, and complex 4.

FADH2 donates two electrons to complex 2, with Hydrogen being pumped at complex 3, and complex 4.

Oxygen acts as the terminal electron acceptor, producing H2O.

FADH2 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 ForceLike 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 YieldA total theoretical yield of 36 (Eukaryotes) or 38 (Prokaryotes) results from a single glucose molecule

Why do you suppose there is a difference?

Experimental YieldExperimentally, 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 ResponseCells 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.

Review1)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 http://www.youtube.com/watch?v=Zgoyi7AK0jg&feature=related5)Compare substrate level phosphorylation and oxidative phosphorylation

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.