Enzymes are proteins that catalyse (speed up) vital chemical reactions inside the body. Enzymes will only function properly under a small range of certain conditions, such as preferred pH and temperature. If any conditions are outside their specific range then the enzymes cannot function. This could cause the organism to die. Homeostasis relies on automatic control systems that include nervous responses (nervous system) or chemical responses (endocrine system). Receptors and effectors are also needed
