Mitochondria arose from aerobic prokaryotes - phagocytosed by eukaryotes. Mitochondria can divide within the cell - k . Inner membrane (cristae) two are intermembrane space. Mitochondria structure: omm the outer mitochondrial membrane: Serves as the outer boundary of the organelle. Has ~ 50% protein : 50% lipid ratio. Has a diverse number of proteins that function as enzymes. Can allow passage of large number of molecules ((e. g. atp) Respond to conditions within the cell e. g. cell stress. Almost 100 different proteins present and has almost no cholesterol. Is rich in a phospholipid called cardiolipin found in many bacterial membrane. Very impermeable to molecules and has many channels & pumps highly selective. Gel-like consistency from the high concentration of proteins and dna. Mitochondrial dna encodes ~ 37 genes in humans. The majority of proteins that function in the mitochondria are encoded by dna in the cell nucleus.