Digestion and absorption of food in insect

An insect uses its digestive system to extract nutrients and other substances from the food it consumes. Most of this food is ingested in the form of macromolecules and other complex substances (such as proteins, polysaccharides, fats, nucleic acids, etc.) which must be broken down by catabolic reactions into smaller molecules (i.e. amino acids, simple sugars, etc.) before being used by cells of the body for energy, growth, or reproduction. This break-down process is known as digestion. Digestibility is just a measure of how much of the nutrients in a sample an animal can actually extract and absorb. Enzyme activity in the midgut varies in relation to food intake, so it is not always clear whether it is synthesis and/or release of the enzymes that is being controlled.