What are the chemicals in the blood that help control the functions of organs called?

The correct answer is hormones, as these are the chemical messengers in the body that play a crucial role in regulating the functions of various organs and systems. Hormones are produced by endocrine glands and released into the bloodstream, where they travel to target organs to initiate specific biological responses. For instance, insulin, produced by the pancreas, helps to regulate blood sugar levels, and adrenaline from the adrenal glands prepares the body for a fight-or-flight response.

Other options, while they play significant roles in biological processes, do not serve the same function as hormones. Enzymes act as catalysts in biochemical reactions but are not responsible for controlling organ functions. Proteins serve a variety of roles in the body, including structural, transport, and immune functions, but again do not function as regulatory messengers like hormones. Additives typically refer to substances added to different products, such as food or medications, and do not fit the definition of chemicals in the blood that regulate organ functions. Therefore, hormones are essential for communication and regulation within the body's systems.