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Question

1.      Describe the structure of the mitochondria, including the location of ATP synthase, high proton concentration, the citric acid cycle, and β-oxidation.

 

2.      What do cytochromes, iron-sulfur clusters, and FAD have in common that allows for electron transport?

3.      Describe the flow of electrons in the ETC, from both NADH and FADH2, to the final electron acceptor. Note any electron carriers. Which steps of ETC involve the movement of hydrogens out of the mitochondrial matrix into the IMS? How and why is this performed?

 

4.      Describe the structure and function of ATP synthase. How does it produce ATP? How many protons are required per ATP?

 

5.      How is oxidative phosphorylation regulated?

 

6.      In photosynthesis:

a.      What is the source of electrons, and what is released?

b.      How are Photosystem I and II different?

c.      How do cyclic and noncyclic photophosphorylation differ?

 

Answer 1

1. Mitochondria possess inner and outer membranes, an intermembrane space and the mitochondrial matrix. The ETC occurs within the inner membrane (with ATP synthase embedded), while B-oxidation and the TCA occur within the matrix.
2. They can participate in reversible redox reactions, meaning they can accept, carry and donate electrons.
3. We begin in either complex 1 or 2. Complex 1 is NADH dehydrogenase, donating electrons from NADH>FMN>FeS Clusters>CoQ. Complex 2 is succinate dehydrogenase, donating electrons from FADH2>CoQ. Complex 3 transfers electrons to and reduces cytochrome C, wheras in complex 4 cytochrome C is oxidized as it donates electrons to oxygen, which is the final electron acceptor. All complexes except complex 2 (insufficient free energy) pump protons to generate a gradient that eventually contributes to ATP synthesis.
4. The F0 portion is embedded within the inner membrane and serves as a "proton channel". The F1 portion is found in the matrix and serves to synthesize ATP. As protons flow back into the matrix, ATP synthase catalyzes a reaction converting ADP + Pi into ATP. We need roughly 4H+ per ATP.
5. Oxidative phosphorylation is regulated by ADP availability, oxygen availability, the proton gradient and NADH/FADH2 supply.
6. Electrons come from H2O, and O2 is released at photosystem II. Photosystem 2 acts first, uses P680, gets electrons from H2O and generates a proton gradient. Photosystem 1 acts second, uses P700, gets electrons from photosystem 2 and produces NADPH. Both cyclic and noncyclic use PS1 and produce ATP, but only noncylic uses PS2, produces NADPH and produces O2.