Energy generation in mitochondria I
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Energy generation in mitochondria I. The overall scheme is known as the chemiosmotic mechanism: Two questions need to be answered: How does electron transport result in the expulsion of protons? How is the inward flow of protons used to drive ATP synthesis?. Refer to chapter 18, Stryer, 5e.

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Refer to chapter 18, Stryer, 5e

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Refer to chapter 18 stryer 5e

Energy generation in mitochondria I

  • The overall scheme is known as the chemiosmotic mechanism: Two questions need to be answered:

  • How does electron transport result in the expulsion of protons?

  • How is the inward flow of protons used to drive ATP synthesis?

Refer to chapter 18, Stryer, 5e

Lecture 22, Michael Schweizer


Refer to chapter 18 stryer 5e

Overview of carbon metabolism in a eukaryotic cell

Karp 3e, Figure 5.5


Refer to chapter 18 stryer 5e

The structure of a mitochondrion

Figure 5.2c


Refer to chapter 18 stryer 5e

Electron Flow produces heat

All chemical energy from electron transfer converted to heat energy

Bio-wire is the respiratory assembly; electron flow produces ATP

Bio-battery


Refer to chapter 18 stryer 5e

Principle of the electron transport chain


Refer to chapter 18 stryer 5e

Respiratory Chain

Electron transfer from NADH to O2 involves multisubunit inner membranecomplexes I, III & IV, plusCoQ&cyt c. Within each complex, electrons pass sequentially through a series of carriers. Complex II exists attached to flavoprotein enzymes.

CoQ is located in the lipid core of the membrane, and there are CoQ binding sites in protein complexes.

Cytochrome c resides in the intermembrane space. It alternately binds to complex III or IV during e- transfer.


Refer to chapter 18 stryer 5e

Vectorial positioned proteins

Proteins in cytoplasm or lumen or organelles are in solution and free-moving

Random orientation of reaction

Proteins in membranes are insoluble and fixed in orientation

Reactions can be directed

Substrates received and products formed vectorially


Refer to chapter 18 stryer 5e

Structure of NADH dehydrogenase, determined by EM


Refer to chapter 18 stryer 5e

  • Respiratory assembly

  • Located in

    plasmamembrane of bacteria

    inner mitochondrial membrane

  • Consists of 4 complexes (I to IV)

    immobilised multiproteins/cofactors

    2 mobile electron shuttles

    Ubiquinone (co-enzyme Q) between I/II and III

    Cytochrome c between III and IV

  • Accepts

    electrons (and H+) from NADH and FADH2 generated

    at numerous oxydation steps

  • Donates

  • electrons to terminal acceptor O2

  • electrons to S, NO3- (inorganic respiration), etc

Bio-wire


Refer to chapter 18 stryer 5e

  • Respiratory chain

    • Propel electrons through multi-enzyme complexes

    • Convert released energy (DG) to form a H+-gradient across membrane

    • Establish a H+ cycle back across membrane

    • Use of H+ cycle to drive ADP + Pi ATP

  • Power transmission by proton gradients:

  • Rotate flagella to propel bacterium

  • Active transport of nutrients into cell

  • Heat production

  • =>Proton gradients are a central interconvertible currency of free energy in biological systems


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