Where is food chemically digested

The pancreas is one of the largest glands in the human body. As well as digestive juices, it secretes a hormone called insulin. Insulin helps to regulate the amount of sugar in the blood. Diabetes is a condition caused by problems with insulin production. Once all the nutrients have been absorbed, the waste is moved into the large intestine, or bowel. Water is removed and the waste faeces is stored in the rectum.

It can then be passed out of the body through the anus. This page has been produced in consultation with and approved by:. The type of pain felt in the abdomen can vary greatly. Children may feel stomach pain for a range of reasons and may need treatment. Being young and fit doesn't reduce your risk of altitude sickness. Around half of cases of anal fissures heal by themselves with proper self-care and avoidance of constipation.

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The movements that propel the food particles through the digestive tract are called peristalsis. These are rhythmic waves of contractions that move the food particles through the various regions in which mechanical and chemical digestion takes place.

The simple molecules that result from chemical digestion pass through cell membranes of the lining in the small intestine into the blood or lymph capillaries. This process is called absorption. The food molecules that cannot be digested or absorbed need to be eliminated from the body. The removal of indigestible wastes through the anus, in the form of feces , is defecation or elimination. Amylases hydrolyze the long carbohydrate chains that break amylose down into disaccharides, and glycogen into polysaccharides.

The enzymes in the small intestine then break these down to monosaccharides. Proteins are digested by hydrolysis of the carbon—nitrogen C—N bond. Peptidases are secreted in an inactive form, to prevent auto-digestion. Endopeptidases cleave the polypeptides at the interior peptide bonds, and the exopeptidases cleave the terminal amino acids. Bile salts emulsify the fats to allow for their solution as micelles in the chyme and to increase the surface area for the pancreatic lipases to operate.

Once the voluntary signal to defecate is sent back from the brain, the final phase begins. Key Terms peptidase : Any enzyme that catalyzes the hydrolysis of peptides into amino acids; a protease. Examples Because amylase turns some potato or rice starch into sugar, these foods taste slightly sweet. Chemical Digestion of Carbohydrates, Proteins, Lipids, and Nucleic Acids The chemical breakdown of the macromolecules contained in food is completed by various enzymes produced in the digestive system.

Learning Objectives Summarize chemical digestion. Key Takeaways Key Points Protein digestion occurs in the stomach and the duodenum through the action of three main enzymes: pepsin, secreted by the stomach, and trypsin and chymotrypsin, secreted by the pancreas. During carbohydrate digestion the bonds between glucose molecules are broken by salivary and pancreatic amylase.

The digestion of certain fats begins in the mouth, where short-chain lipids break down into diglycerides because of lingual lipase. The fat present in the small intestine stimulates the release of lipase from the pancreas, and bile from the liver enables the breakdown of fats into fatty acids.

Key Terms zymogen : A proenzyme, or enzyme precursor, that requires a biochemical change i. Licenses and Attributions. CC licensed content, Shared previously. In contrast to the water-soluble nutrients, lipid-soluble nutrients can diffuse through the plasma membrane.

Once inside the cell, they are packaged for transport via the base of the cell and then enter the lacteals of the villi to be transported by lymphatic vessels to the systemic circulation via the thoracic duct. The absorption of most nutrients through the mucosa of the intestinal villi requires active transport fueled by ATP. The routes of absorption for each food category are summarized in Table All carbohydrates are absorbed in the form of monosaccharides.

The small intestine is highly efficient at this, absorbing monosaccharides at an estimated rate of grams per hour.

All normally digested dietary carbohydrates are absorbed; indigestible fibers are eliminated in the feces. The monosaccharides glucose and galactose are transported into the epithelial cells by common protein carriers via secondary active transport that is, co-transport with sodium ions. The monosaccharides leave these cells via facilitated diffusion and enter the capillaries through intercellular clefts.

The monosaccharide fructose which is in fruit is absorbed and transported by facilitated diffusion alone. The monosaccharides combine with the transport proteins immediately after the disaccharides are broken down. Secondary active transport mechanisms, primarily in the duodenum and jejunum, absorb most proteins as their breakdown products, amino acids.

These mechanisms are conceptually identical to the absorptive processes involved in monosaccharide absorption. Almost all 95 to 98 percent protein is digested and absorbed in the small intestine. The type of carrier that transports an amino acid varies. Most carriers are linked to the active transport of sodium. Short chains of two amino acids dipeptides or three amino acids tripeptides are also transported actively.

However, after they enter the absorptive epithelial cells, they are broken down into their amino acids before leaving the cell and entering the capillary blood via facilitated diffusion. About 95 percent of lipids are absorbed in the small intestine. Bile salts not only speed up lipid digestion, they are also essential to the absorption of the end products of lipid digestion. Short-chain fatty acids are relatively water soluble and can enter the absorptive cells enterocytes directly. Despite being hydrophobic, the small size of short-chain fatty acids enables them to be absorbed by enterocytes via simple diffusion, and then take the same path as monosaccharides and amino acids into the blood capillary of a villus.

The large and hydrophobic long-chain fatty acids and monoacylglycerides are not so easily suspended in the watery intestinal chyme. However, bile salts and lecithin resolve this issue by enclosing them in a micelle , which is a tiny sphere with polar hydrophilic ends facing the watery environment and hydrophobic tails turned to the interior, creating a receptive environment for the long-chain fatty acids.

The core also includes cholesterol and fat-soluble vitamins. Without micelles, lipids would sit on the surface of chyme and never come in contact with the absorptive surfaces of the epithelial cells. Micelles can easily squeeze between microvilli and get very near the luminal cell surface.

At this point, lipid substances exit the micelle and are absorbed via simple diffusion. The free fatty acids and monoacylglycerides that enter the epithelial cells are reincorporated into triglycerides.

The triglycerides are mixed with phospholipids and cholesterol, and surrounded with a protein coat. This new complex, called a chylomicron , is a water-soluble lipoprotein. After being processed by the Golgi apparatus, chylomicrons are released from the cell Figure Too big to pass through the basement membranes of blood capillaries, chylomicrons instead enter the large pores of lacteals.

The lacteals come together to form the lymphatic vessels.