Gene expression in eukaryotes can be regulated at various levels. Certain mutations in flies may cause them to develop an extra set of legs or wings. , which determine the formation and arrangement of body parts in multicellular organisms, control gene expression by regulation of .

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.