CIE IGCSE Biology: 复习笔记:7.1.7 Chemical Digestion

CIE IGCSE Biology: 复习笔记:7.1.7 Chemical Digestion

Chemical Digestion

Stages of food breakdown

  • Food taken into the body goes through 5 different stages during its passage through the alimentary canal (the gut):
    • Ingestion - the taking of substances, e.g. food and drink, into the body through the mouth
    • Mechanical digestion - the breakdown of food into smaller pieces without chemical change to the food molecules
    • Chemical digestion - the breakdown of large, insoluble molecules into small, soluble molecules
    • Absorption - the movement of small food molecules and ions through the wall of the intestine into the blood
    • Assimilation - the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells
    • Egestion - the passing out of food that has not been digested or absorbed, as faeces, through the anus
  •  The role of chemical digestion is to produce small soluble molecules that can be absorbed