To determine whether all living cells you saw in the lab contained mitochondria, you would need to consider the characteristics of prokaryotic cells, such as E. coli and Anabaena. Prokaryotic cells, unlike eukaryotic cells, lack membrane-bound organelles, including mitochondria. Therefore, it is safe to conclude that the prokaryotic cells you observed during the lab do not contain mitochondria.
Referring to the second question, a chemical signal that acts as a messenger is generally known as a hormone. Hormones are molecules produced by various glands in the body and are released into the bloodstream to signal and regulate the activity of different cells and organs.
Hormones are essential in maintaining homeostasis, coordinating growth and development, regulating metabolism, and controlling various physiological processes in the body. They help transmit information between cells, tissues, and organs, enabling the body to respond and adapt to different stimuli, such as stress, growth, reproduction, and behavior. Overall, hormones play a crucial role in maintaining the proper functioning of the body's systems.