Final answer:
Not all eukaryotic cells contain classic mitochondria; some have reduced mitochondrial remnants, and a few appear to lack them entirely. However, these are exceptions to the rule that most eukaryotic cells depend on mitochondria for cellular respiration and energy production.
Step-by-step explanation:
The correct answer to whether all eukaryotic cells contain mitochondria is 'No, but some exceptions; minimal impact on cellular respiration'.
While mitochondria are indeed present in the vast majority of eukaryotic cells and are crucial for cellular respiration, there are exceptions. Some eukaryotic organisms have reduced mitochondrial remnants, such as hydrogenosomes and mitosomes. Additionally, a few types of protozoa seem to lack mitochondria altogether, challenging the notion that all modern eukaryotes have direct lineages that include classic mitochondria. These organisms might have once had mitochondria that were lost over evolutionary time. Mitochondria are responsible for producing ATP through cellular respiration, but some cells can use anaerobic pathways or alternative organelles to produce energy. Nonetheless, the lack of mitochondria could fundamentally alter a cell's metabolism and its ability to generate energy.