That's correct! Mitochondria are often referred to as the "powerhouses" of the cell because they play a crucial role in the process of cellular respiration, where glucose is broken down to produce ATP (adenosine triphosphate), the primary energy carrier in cells.
In the absence of mitochondria, cells cannot efficiently perform aerobic respiration, which is the process that occurs in mitochondria and yields a significant amount of ATP from glucose. Without mitochondria, cells may rely on anaerobic processes, such as fermentation, which produce far less ATP per glucose molecule.
For example, in human muscles during intense exercise, oxygen may become limiting, leading to anaerobic glycolysis, which converts glucose to lactic acid and generates only 2 ATP per glucose molecule, in contrast to the approximately 30-32 ATP produced through aerobic respiration in the mitochondria.
Some specialized cell types, such as certain red blood cells in mammals, indeed lack mitochondria and rely exclusively on anaerobic glycolysis for their energy needs. However, this results in a much lower energy yield compared to cells with functioning mitochondria.