Biology · Biochemistry & Cellular Respiration

Consider the following statements about the inner mitochondrial membrane (IMM) and oxidative phosphorylation: I. The IMM is the most protein-rich membrane in the cell (~75% protein by mass) and is virtually impermeable to protons, which is essential for the chemiosmotic gradient. II. Cardiolipin (bisphosphatidylglycerol) is enriched in the IMM, where it stabilises respiratory chain supercomplexes (respirasomes) and is required for cytochrome c retention. III. The stoichiometry of the human ATP synthase c-ring (8 c-subunits) predicts ~3.3 H+ translocated per ATP synthesised, which together with proton transport stoichiometries of Complexes I, III, and IV gives a theoretical P/O ratio of ~2.5 for NADH. IV. Uncoupling protein 1 (UCP1) in brown adipose tissue generates heat by allowing K+ ions to leak across the IMM, dissipating the mitochondrial membrane potential. Which statements are correct?