Final answer:
The inner mitochondrial membrane has a high protein concentration because of its role in the electron transport chain, ATP production, and housing of mitochondrial DNA and ribosomes. Cristae increase the surface area for these reactions, and the transfer of proteins post-translationally contributes to the protein density.
Step-by-step explanation:
The inner mitochondrial membrane has a very high concentration of protein due to several key functions it serves in cellular respiration and energy production. The membrane's structure, derived from a bacterial plasma membrane, features an extensive network of cristae, which are invaginations that increase the surface area available for biochemical reactions, particularly for the electron transport chain (ETC) and ATP synthesis. Proteins like FF₁ATPase, integral to this inner membrane, are critical for the conversion of energy liberated from the ETC into ATP through a process of conformational change. The inner membrane also houses mitochondrial DNA and 70S ribosomes involved in the production of mitochondrial proteins, thus further increasing its protein concentration.
Moreover, the post-translational transfer of proteins into the mitochondria involves the recognition and binding of a signal peptide on the folded protein to receptor proteins at the mitochondrial membranes. Subsequently, these proteins integrate into the inner mitochondrial membrane, adding to its protein density. In muscle cells, which require abundant energy for contraction, the concentration of mitochondria and thus their inner membrane proteins is exceptionally high, emphasizing the form and function relationship.