Please choose the correct ending to complete the given sentence: Education and Communications: [header] How to contrast biochemical reactions inside the body and chemical reactions in the chemistry laboratory [title] Define metabolic reactions. [step] Metabolic reactions refer to biochemical reactions that take place inside the body of living systems. This includes mammalians and microorganisms in addition to plants.

Ending1: [substeps] Regulate the extent of metabolic reactions to distinguish them from outside or inside the body. Humans are categorized by their biochemical reactions. Ending2: This type of chemical reactions is characteristic of living tissues only. It is not observed in the chemistry laboratory for example. Ending3: They are both often called metabolic reactions because they form automatic connections between different bodies of the system. For instance, instead of a human's body producing gas, an electric circuit will create electricity generated from cells. Ending4: Motor reactions are physical reactions that take place in the body. They contain biological reactions that attack the environment, environmental reactions, and chemical reactions used for physical actions.

Answer format: ending1/ending2/ending3/ending4