sentences: cellular respiration is when a cell converts from oxygen and carbohydrates into carbon dioxide, water, and energy & inanimate nothing require magnesium to waste matter ->  living things must convert oxygen into carbon dioxide to use energy  living things must convert oxygen into carbon dioxide to use energy & breathing is when animals convert oxygen into carbon dioxide -> inanimate nothing optional breathe to waste matter living things must breathe to use energy  breathing out is when animals exhale carbon dioxide from their lungs into the air & animals are a source of carbon dioxide by exhaling -> people are a sink of oxygen oxygen by smother animals are a source of carbon dioxide by breathing  people are a sink of oxygen oxygen by smother & a source of something produces that something -> animals produce carbon dioxide by breathing animals produce carbon dioxide by breathing  living things must breathe to use energy & people wreck oxygen oxygen by smother -> animals produce carbon dioxide by using energy