Final answer:
The outer membrane of mitochondria is more permeable than the inner membrane, which is specialized and contains the electron transport chain for ATP synthesis.
Step-by-step explanation:
The outer membrane of mitochondria is more permeable than the inner membrane. Mitochondria consist of two membranes: the smooth outer membrane which separates the mitochondrion from the cytosol, and the inner membrane, which contains many folds known as cristae. While both membranes are phospholipid bilayers, they have different roles and properties. The outer membrane is relatively permeable to small molecules and ions due to the presence of protein channels known as porins. In contrast, the inner membrane is less permeable and is the site of ATP synthesis; it contains specific transport proteins that regulate the passage of substances in and out of the mitochondrial matrix. Additionally, the inner mitochondrial membrane houses the electron transport chain and matrix, essential for aerobic respiration. The permeability of the inner membrane is tightly controlled to maintain the mitochondrial function.