This document outlines the fundamentals of cellular respiration, focusing on both aerobic and anaerobic processes. It details the types of organisms that perform each type of respiration, with aerobic respiration happening in eukaryotic cells such as animals, plants, and fungi, while anaerobic respiration occurs in both prokaryotes and eukaryotes under low-oxygen conditions, such as yeast and bacteria. The document elaborates on the key metabolic pathways involved, including Glycolysis, the Krebs Cycle, and the Electron Transport Chain (ETC), along with the amounts of ATP produced from each process. It serves as an introductory resource for understanding how organisms generate energy under varying environmental conditions.