Lec 20 note - LECTURE 20 08 October 2010(P J Hollenbeck...

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-1- LECTURE 20 08 October 2010 (P. J. Hollenbeck) BIOL231 Mitochondria II: Transport functions and evolution Read pp. 487-491; Problems: 54-58; Exam II’06, #8; ECB Q14-4, 14-20 I. Transport across the IMM <The relative impermeability of the inner mitochondrial membrane makes oxidative phosphorylation possible. But it also requires the presence of specific transporters to move essential molecules between the matrix and the IMS/cytoplasm.> (A) Transport can be coupled directly to H flowing down the electrochemical gradient + (1) Pyruvate transport. There wouldn’t be much point in having the TCA cycle within the matrix if the mitochondrion couldn’t efficiently move pyruvate (derived from glycolysis) from the cytoplasm into the matrix to supply it. A symporter in the IMM couples the energetically favorable flow of H down its gradient (IMS/cytoplasm => + matrix) to the movement of pyruvate in the same direction. ii i (2) Phosphate (P ) transport. P is required for the reaction ADP + P => ATP to occur i at the matrix side of the ATP synthase complex. In a similar manner to pyruvate, P is imported from the cytoplasm/IMS into the matrix by a symporter in the IMM. This i couples the energetically favorable flow of H into the matrix to the transport of P in + i the same direction, providing the high [P ] necessary for ATP synthesis. (B) Transport can be driven indirectly by the electrochemical gradient across the IMM. ATP is produced primarily in the mitochondrial matrix and hydrolyzed primarily in the cytoplasm. Thus, moving ATP out of the matrix and ADP into the matrix is absolutely essential for the continued production of ATP and the life of the aerobic cell. A carrier protein in the IMM (the adenine nucleotide transporter, or ANT) exchanges ATP on one side of the membrane for ADP on the other. Thus we can call it an IMM antiporter . It normally runs in the correct direction because of the charge difference between ADP and ATP.
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This note was uploaded on 09/18/2011 for the course BIOLOGY 231 taught by Professor Petethollenbeck during the Fall '10 term at Purdue.

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Lec 20 note - LECTURE 20 08 October 2010(P J Hollenbeck...

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