Which organelle in eukaryotic cells is the site of the Krebs cycle and the electron transport pathway?

The mitochondrion is recognized as the powerhouse of the cell and is responsible for the processes involved in energy production. Within the mitochondrion, the Krebs cycle (also known as the citric acid cycle) occurs in the mitochondrial matrix. This cycle is crucial for the oxidation of nutrients, leading to the release of energy stored in chemical bonds.

Following the Krebs cycle, the electron transport chain, which is critical for ATP production, takes place across the inner mitochondrial membrane. This pathway involves a series of protein complexes that facilitate the transfer of electrons and the pumping of protons, ultimately producing ATP through oxidative phosphorylation.

The other organelles listed serve different functions: the nucleus is the control center for cellular activity and houses genetic material; lysosomes are involved in waste processing and digestion of cellular debris; and the endoplasmic reticulum is primarily involved in protein synthesis and lipid metabolism. Thus, the mitochondrion stands out as the organelle where both the Krebs cycle and the electron transport pathway occur, making it essential for cellular respiration and energy production.