The mitochondrial inner membrane is protein-rich, at:

1. A membrane packed with electron transport machinery needs a great deal of protein. 2. The mitochondrial inner membrane contains 76 percent protein and only 24 percent lipid. 3. 24 percent is its lipid share, so that option inverts the answer. 4. This is the mirror image of myelin, which is mostly lipid. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 5 'Structure and Function of Plasma Membranes', sections 5.1-5.4_