The main function is to break down lactose in the body. when you are lactose intolerant (which most adults are to a degree) then tactasr is no longer funtioning properly and lactose isnt being broken down
Lactase protein acts as a digestive enzyme whose main function is to break down the lactose sugar. Lactose is found in milk and other dairy products. Lactose sugar is a big molecule and thus it is difficult to metabolize it. Lactase breaks down the lactose into smaller molecules such as glucose and galactose, which are easily absorbed by the intestine.
Carbon dioxide and water are known as byproducts. Please take note that respiration and photosynthesis are basically the exact opposite of each other. Respiration takes diatomic oxygen or simply O2 from the atmosphere and changes it with carbon dioxide or CO2. On the other hand, photosynthesis takes out CO2 from the atmosphere and changes it with O2.