Question 1: (10 pts) Seven electron transport chain (ETC) protein complexes (but

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Question 1: (10 pts) Seven electron transport chain (ETC) protein complexes (but not ATP synthase) of a new uncharacterized mammalian species have been successfully purified. These proteins essentially work like canonical ETC complexes in other mammals: electron carriers (such as NADH, etc.) wil donate their electrons to a complex, those electrons will flow through the complex, and get donated to the next electron carrier in chain, and so forth. You decide to label the 7 ETC complexes A-G corresponding to ascending size (Complex A is 30kDa, Complex B is ~80 kDa, etc.). A series of drugs were discovered, labeled Drugs A-G corresponding to the ETC complex that it inhibits (Drug A inhibits Complex A, etc.). You also know that the chain requires electron flow through 8 electron carriers: FADH2, NADH, and 6 randomly labeled acceptors E1-E6. When the drugs were used on a reconstituted, working ETC system with abundant electron carriers, the following was found after all electron flow had completed: A. Oxidized FADH2, E1, E2, E4, E5, E6 FADH2, E1, E2, E3, E4, E5, E6 E1, E4 Drug Used Drug A Drug B Drug C Drug D Drug E Drug F Drug G Reduced NADH, E3 NADH NADH, FADH2, E2, E3, E5, E6 NADH, FADH2, E1, E2, E3, E5, E6E4 NADH, E3, E5 NADH, E2, E3, E5 FADH2 FADH2, E1, E2, E4, E6 FADH2, E1, E4, E6 NADH, E1, E2, E3, E4, E5, E6 *remember that drugs are named after the ETC complex they inhibit. (Drug A inhibits complex A, etc.) To which complex do FADH2 and NADH donate their electrons, respectively? (2 pts) Using the table above, determine the sequence of electron transport chain events. Draw a flowchart (like in Problem Set 7) and include the following information: 1) the ETC complexes in the correct sequence, 2) the flow of electron carriers, and 3) the drugs, connected to the complex they inhibit respectively. (8 pts) B.

Explanation / Answer

An electron from NADH is first accepted by the protein complex NADH-Q reductase, also known as the NADH dehydrogenase complex. This is the largest of the electron carriers, consisting of more than 22 protein chains. The NADH-Q reductase complex accepts an electron from NADH and passes the electron to the next electron carrier, ubiquinone, which has a higher reduction potential.

Coenzyme-Q receives the electrons derived from NADH from complex I and the electrons derived from FADH2 from complex II,

Electron transport Chain

NADH – NAD+ - FADH – FAD+ - Co-Q- Co-QH - Cyt-b - Cyt-b6 - Cyt-C – Cyt-a – Cyt-a3

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