The term "body chemistry" refers to the complex mixture of chemical reactions that take place in a living organism. It includes the processes by which food is broken down, nutrients are absorbed and utilized, waste products are excreted, hormones and other signaling molecules are produced and interact with their target cells, and many other metabolic activities. These chemical reactions involve various substances such as enzymes, hormones, neurotransmitters, and other signaling molecules that work together to maintain the proper function of an organism's body systems.