MCAT Question of the Day
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    Q:

    		 ATP can be generated by oxidative phosphorylation in the mitochondria via the electron transport chain, which comprises of a series of hydrogen pumps, electron carriers and ATP synthase. An electrochemical H+ gradient is produced across the inner mitochondrial membrane when H+ is pumped (driven by redox reactions within the proton pump complexes) from the matrix into the intermembrane space. The return of H+ into the matrix through ATP synthase drives the synthesis of ATP. Oligomycin is a macrolide (type of antibiotic) that inhibits the proton channel (F0 subunit) of ATP synthase. Dinitrophenol (DNP) is a known metabolic poison that uncouples oxidative phosphorylation by carrying protons across the inner mitochondrial membrane from the intermembrane space to the matrix. What is an expected result when both oligomycin and DNP are present in mitochondria?

    		 

    A

    		 The actions of oligomycin and DNP cancel each other out. There is no net effect on regular oxidative phosphorylatiive ATP generation. ATP is produced as normal.

    B

    		 ATP is not produced but a lot of heat is generated.

    C

    		 ATP is generated, but less than normal.

    D

    		 ATP is not produced and the proton pumps of the ETC stop pumping protons from the matrix to the intermembrane space.



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