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Unformatted text preview: he transporter. (The mitochondrial inner membrane has no transporter for oxaloacetate.) (The data presented in the table do not exclude the possibility that malate just has an allosteric stimulatory effect on citrate transport. To investigate this point, one could try the experiment in reverse: see whether adding citrate stimulates efflux of malate. A more definitive demonstration would require showing that stoichimetric amounts of the two acids move in opposite directions.) Citrate efflux cannot not driven by ATP in the absence of malate (row 3), but is accelerated by ATP if malate is present (row 7). The effect of ATP is not seen in the presence of the uncoupler FCCP (row 9), suggesting that it involves a transmembrane electrochemical potential. (Uncouplers are lipophilic weak acids that can carry protons across biological membranes. FCCP would collapse any electrochemical potential difference across the mitochondrial inner membrane.) An electric potential difference could affect citrate/malate exchange because citrate has a charge of -3 at physiological pH, while malate has a...
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This note was uploaded on 02/02/2010 for the course BIOCHEMIST Biochem 44 taught by Professor Parson,young during the Winter '10 term at University of Washington.
- Winter '10