Which structure is responsible for ATP production in eukaryotic cells?

The mitochondria are the structures primarily responsible for ATP production in eukaryotic cells. These organelles are often referred to as the "powerhouses" of the cell due to their critical role in cellular respiration, which is the metabolic process through which cells convert nutrients into energy. Mitochondria generate ATP through oxidative phosphorylation, a process that takes place in the inner mitochondrial membrane.

During cellular respiration, glucose and other substrates are broken down, and the energy released is used to produce ATP from ADP and inorganic phosphate. Mitochondria possess their own DNA and ribosomes, allowing them to synthesize some of the proteins necessary for their function. This unique feature supports the endosymbiotic theory, which posits that mitochondria were once free-living bacteria that became integrated into eukaryotic cells.

The other structures mentioned have distinct roles but do not produce ATP as their primary function. The nucleus is involved in storing genetic material and regulating gene expression, ribosomes are responsible for protein synthesis, and the endoplasmic reticulum plays a crucial role in protein and lipid synthesis, but none of these structures are directly involved in ATP production.