Multiple Choice
In the context of principles of transmembrane transport, which statement correctly describes the difference between simple diffusion and facilitated diffusion across a cell membrane?
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9. Transport Across Membranes
Principles of Transmembrane Transport
Multiple Choice
In mammalian cells, how does cytosolic pyruvate enter the mitochondrial matrix for oxidation by the pyruvate dehydrogenase complex?
A
By vesicular endocytosis of pyruvate into the mitochondrial matrix
B
By simple diffusion through the inner mitochondrial membrane because pyruvate is nonpolar
C
By direct passage through the -ATP synthase channel as a coupled import mechanism
D
By transport across the inner mitochondrial membrane via the mitochondrial pyruvate carrier (MPC), a specific pyruvate transporter
Verified step by step guidance1
Understand that pyruvate, produced in the cytosol by glycolysis, must enter the mitochondrial matrix to be oxidized by the pyruvate dehydrogenase complex (PDC).
Recall that the inner mitochondrial membrane is highly impermeable to most molecules, including pyruvate, so simple diffusion is not possible.
Recognize that vesicular endocytosis is a process used for transporting large molecules or particles into cells, not for small metabolites like pyruvate into mitochondria.
Know that the F\_oF\_1-ATP synthase is involved in ATP synthesis and proton transport, not in pyruvate transport.
Conclude that pyruvate enters the mitochondrial matrix via a specific transporter protein called the mitochondrial pyruvate carrier (MPC), which facilitates its transport across the inner mitochondrial membrane.
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