Practice question

Mitochondria originated from alphaproteobacterial endosymbiont engulfed by archaeal host over 1.5 billion years ago, retaining circular mitochondrial DNA, bacterial-type transcription and translation machinery including 55S mitoribosomes, and binary fission mediated by Drp1 and dynamin-like proteins, with genomes encoding core subunits of oxidative phosphorylation. Inner membrane houses respiratory chain complexes I to IV transferring electrons from NADH and FADH2 to oxygen producing proton gradient used by F0F1 ATP synthase to generate ATP, central to aerobic metabolism. This organelle occurs in virtually all eukaryotes capable of aerobic or facultative anaerobic metabolism: animal cells with high demand like cardiomyocytes containing thousands mitochondria, plant leaf cells where mitochondria coexist with chloroplasts and participate in photorespiration converting glycolate, yeast, algae, protozoa, only missing in some anaerobic protists that contain hydrogenosomes derived from mitochondria. Claiming presence only in animal cells contradicts inclusion in plant root and shoot cells, fungi, and broad eukaryotic distribution, as microscopy and biochemistry clearly demonstrate mitochondrial markers across kingdoms.