Final answer:
Oxygen and carbon dioxide can easily pass through the outer membrane of mitochondria due to simple diffusion. They are nonpolar molecules with low molecular weight, which allows them to move freely through the lipid bilayer without the need for transport proteins.
Step-by-step explanation:
Based on the function of mitochondria, the substance able to pass through the outer membrane of the mitochondria easily is oxygen and carbon dioxide. These are small molecules with no charge, which allows them to pass through membranes by simple diffusion. Unlike ions or polar substances, which require special means to penetrate the plasma membrane due to their charge or polarity, oxygen and carbon dioxide can move freely through the lipid bilayer because they are nonpolar and have low molecular weight.
The outer membrane of the mitochondria is similar to the plasma membrane in that it is amphipathic with hydrophilic and hydrophobic regions. This outer membrane is designed to be permeable, especially to small, nonpolar molecules. The structure of the mitochondrion is crucial for its role in aerobic respiration, as its inner membrane is where most of the cell's ATP is made.