In a mitochondrion, what is the mitochondrial matrix?

• A. The folded portions of the inner mitochondrial membrane that house the electron transport chain complexes
• B. The innermost compartment enclosed by the inner mitochondrial membrane that contains enzymes for the citric acid cycle, mitochondrial DNA, and ribosomes
• C. The outermost membrane of the organelle that contains porin channels and encloses the entire mitochondrion
• D. The space between the outer and inner mitochondrial membranes where protons accumulate during oxidative phosphorylation

Answer: (B)