![]() ![]() All mammals have teeth and can chew their food to begin the process of physically breaking it down into smaller particles. The food is broken into smaller particles by mastication, the chewing action of the teeth. The components of the human digestive system are shown.īoth physical and chemical digestion begin in the mouth or oral cavity, which is the point of entry of food into the digestive system. The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces it is stored until it is excreted through the anus.įigure 1. ![]() ![]() ![]() The smaller molecules are absorbed into the blood stream through the epithelial cells lining the walls of the small intestine. Further breakdown of food takes place in the small intestine where bile produced by the liver, and enzymes produced by the small intestine and the pancreas, continue the process of digestion. This acidity kills microorganisms, breaks down food tissues, and activates digestive enzymes. The stomach contents are extremely acidic, with a pH between 1.5 and 2.5. Using peristalsis, or wave-like smooth-muscle contractions, the muscles of the esophagus push the food toward the stomach. The food is then swallowed and enters the esophagus-a long tube that connects the mouth to the stomach. The enzymes present in saliva also begin to chemically break down food. The teeth play an important role in masticating (chewing) or physically breaking food into smaller particles. The process of digestion begins in the mouth with the intake of food ( Figure 1). The rise in obesity and the resulting diseases like type 2 diabetes makes understanding the role of diet and nutrition in maintaining good health all the more important. Taking in more food energy than is used in activity leads to storage of the excess in the form of fat deposits. One of the challenges in human nutrition is maintaining a balance between food intake, storage, and energy expenditure. This happens by both physical means, such as chewing, and by chemical means. During digestion, food particles are broken down to smaller components, which are later absorbed by the body. The conversion of the food consumed to the nutrients required is a multistep process involving digestion and absorption. Animals must convert these macromolecules into the simple molecules required for maintaining cellular function. However, the food consumed consists of protein, fat, and complex carbohydrates. At the cellular level, the biological molecules necessary for animal function are amino acids, lipid molecules, nucleotides, and simple sugars. While plants can obtain nutrients from their roots and the energy molecules required for cellular function through the process of photosynthesis, animals obtain their nutrients by the consumption of other organisms. Theme 4: How Do Diet, Exercise and Weight Affect Health?Īll living organisms need nutrients to survive. Substances in food that must be chemically digested include carbohydrates, proteins, lipids, and nucleic acids. Which is part of food must be chemical digested?Ĭhemical digestion is the biochemical process in which macromolecules in food are changed into smaller molecules that can be absorbed into body fluids and transported to cells throughout the body. In chemical digestion, enzymes break down food into the small molecules the body can use. Mechanical digestion refers to the physical breakdown of large pieces of food into smaller pieces which can subsequently be accessed by digestive enzymes. How does mechanical digestion relate to chemical digestion? Also in the mouth, an enzyme called salivary amylase begins to break down long starch molecules into maltose. It starts the process of mechanical digestion by grinding the food with teeth. What happens to long starch molecules during digestion?ĭigestion is the breakdown of food into simpler molecules that can be absorbed by the body. Similarly, what happens to fats during digestion? What happens to macromolecules from food during digestion?Ĭhemical digestion is a chemical process in which macromolecules - including carbohydrates, proteins, lipids, and nucleic acids - in food are changed into simple nutrient molecules that can be absorbed into body fluids. The enzyme pepsin plays an important role in the digestion of proteins by breaking them down into peptides, short chains of four to nine amino acids. A large part of protein digestion takes place in the stomach. When large proteins are chemically digested they are broken up into many smaller? ![]()
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