chemical digestion

Examples of chemical digestion in the following topics:

• Chemical Digestion of Carbohydrates, Proteins, Lipids, and Nucleic Acids

  • Chemical breakdown of macromolecules contained in food is completed by various enzymes produced in the digestive system.
  • The digestive enzymes, however, are secreted mainly as their inactive precursors, the zymogens.
  • Sucrose digestion yields the sugars fructose and glucose, which are readily absorbed by the small intestine.
  • Digestion of certain fats begins in the mouth, where lingual lipase breaks down short chain lipids into diglycerides.
  • Complete digestion of one molecule of fat (a triglyceride) results in three fatty acid molecules and one glycerol molecule.

• Processes and Functions of the Digestive System

  • Digestion is necessary for absorbing nutrients from food, and occurs through two processes: mechanical and chemical digestion.
  • This mechanical and chemical breakdown encompasses the process of digestion.
  • (1) Mechanical Digestion: larger pieces of food get broken down into smaller pieces while being prepared for chemical digestion, this process starts in the mouth and continues into the stomach.
  • (2) Chemical Digestion: starts in the mouth and continues into the intestines.
  • There are at least five major digestive hormones in the gut of mammals that help process food through chemical digestion.

• Mechanisms of Chemical Digestion

  • Chemical digestion is the process of breakdown of large macronutrients into smaller molecules by enzyme-mediated hydrolysis.
  • Proteins and polypeptides are digested by hydrolysis of the C-N bond .
  • Stomach pepsin digests about 20% of the proteins, the rest is digested by pancreatic and small intestine enzymes.
  • Proteins and polypeptides are digested by hydrolysis of the C-N bond.
  • Differentiate among the methods used to chemically break down food molecules

• Digestion and Absorption

  • In order for nutrients (carbohydrates, lipids, vitamins) to be absorbed for energy, food must undergo chemical and mechanical digestion.
  • Digestion is the mechanical and chemical break down of food into small organic fragments.
  • In chemical digestion, enzymes break down food into the small molecules the body can use.
  • Digestive enzymes are found in the digestive tracts of animals.
  • Mechanical and chemical digestion of food takes place in many steps, beginning in the mouth and ending in the rectum.

• Digestive Processes of the Small Intestine

  • The small intestine uses different enzymes and processes to digest proteins, lipids, and carbohydrates.
  • The small intestine is where most chemical digestion takes place.
  • The three major classes of nutrients that undergo digestion are proteins, lipids (fats), and carbohydrates.
  • Chemical breakdown begins in the stomach and continues through the large intestine.
  • Other carbohydrates pass undigested into the large intestine, where they are digested by intestinal bacteria.

• Digestive System: Mouth and Stomach

  • The extensive chemical process of digestion begins in the mouth.
  • A large part of digestion occurs in the stomach .
  • This highly-acidic environment is required for the chemical breakdown of food and the extraction of nutrients.
  • Chemical digestion is facilitated by the churning action of the stomach.
  • Digestion of food begins in the (a) oral cavity.

• Vertebrate Digestive Systems

  • Humans and many animals have a monogastric digestive system .
  • The enzymes present in saliva also begin to chemically break down food.
  • Most of the chemical digestion and absorption happens in the intestine, while the waste is excreted through the cloaca.
  • The digestive enzymes of these animals cannot break down cellulose, but microorganisms present in the digestive system can.
  • This is the site where the roughage is fermented and digested.

• Digestion in the Mouth, Pharynx, and Esophagus

  • Digestion is the mechanical and chemical breakdown of food into smaller components that are more readily absorbed into the bloodstream.
  • Digestion is the mechanical and chemical breakdown of food into smaller components so that it can be more readily absorbed into the bloodstream.
  • When food enters the mouth, digestion begins with the action of mastication, a form of mechanical digestion, and with the contact of saliva.
  • It cleans the oral cavity, moistens the food, and contains digestive enzymes.
  • It lies cranial, or superior, to the esophagus and forms part of the digestive and respiratory systems.

• Digestive Systems

  • During digestion, food particles are broken down to smaller components which will later be absorbed by the body.
  • The digestive system is one of the largest organ systems in the human body.
  • The cells of the human body all require a wide array of chemicals to support their metabolic activities, from organic nutrients used as fuel to the water that sustains life at the cellular level.
  • The digestive system not only effectively chemically reduces the compounds in food into their fundamental building blocks, but also acts to retain water and excrete undigested materials.
  • The functions of the digestive system can be summarized as follows: ingestion (eat food), digestion (breakdown of food), absorption (extraction of nutrients from the food), and defecation (removal of waste products).

• Hormonal Responses to Food

  • The system is made of a series of glands that produce chemicals called hormones.
  • These hormones are chemical mediators released from endocrine tissue into the bloodstream where they travel to target tissue and generate a response.
  • In the duodenum, digestive secretions from the liver, pancreas, and gallbladder play an important role in digesting chyme during the intestinal phase.
  • Foods high in lipids (fatty foods) take a long time to digest.
  • Hormones, such as secretin and cholecystokinin, play important roles in digestive processes.