a) Where does chemical digestion begin? What is the first enzyme to access food
ID: 3508222 • Letter: A
Question
a) Where does chemical digestion begin? What is the first enzyme to access food that is ingested? What macromolecule does this enzyme digest? Where is this enzyme produced/secreted?
b) Does the stomach produce any enzymes or other factors that can be used to break down food? If so, what macromolecules do these factors digest and what cells produce these factors?
c) What accessory organ(s) produce(s) digestive enzymes? What are the names of the enzymes that are produced? Where do these enzymes enter the gastrointestinal tract? Be as specific as possible.
d) What is the purpose of bile salts in food digestion? Where are bile salts produced? Where are they stored? What stimulates their secretion into the gastrointestinal tract?
2)
a) What type of muscle cells are located within the wall of the small intestine? In what layer(s) of the small intestine wall can they be found? How are these muscle cells oriented?
b) What are the three main types of motility that occur within the gastrointestinal tract and what purpose does each serve?
c) Describe, in detail, the absorption of monosaccharides (specifically glucose and fructose) by intestinal cells. Be sure to include any specific transport proteins that are involved in the migration of these molecules into intestinal cells as well as their release into circulation.
3)
a) What cells are responsible for absorbing nutrients from the gastrointestinal lumen? Where in the gastrointestinal tract does the majority of nutrient absorption occur?
b) What effect does surface area have on the absorption of nutrients? How does the gastrointestinal tract increase its surface area?
c) In what form are lipids absorbed in the gastrointestinal tract? How are they absorbed?
Explanation / Answer
a.Where does chemical digestion begin? What is the first enzyme to access food that is ingested? What macromolecule does this enzyme digest? Where is this enzyme produced/secreted?
Chemical digestion begins in mouth. The enzyme amylase, found in saliva, it starts breaking down carbohydrates. Salivary amylase is produced by the salivary glands.
b.Does the stomach produce any enzymes or other factors that can be used to break down food? If so, what macromolecules do these factors digest and what cells produce these factors?
Chemical digestion further continues in the stomach. Hydrochloric acid and the enzyme pepsin work on digesting proteins. Also mechanical digestion takes place in the stomach as it churns out the food and make chyme. Gastric glands produce the gastric juice which is the mixture of hcl and pepsin.
c.What accessory organ(s) produce(s) digestive enzymes? What are the names of the enzymes that are produced? Where do these enzymes enter the gastrointestinal tract? Be as specific as possible.
Accessory organs to the GI tract are Salivary glands, liver, gall bladder, and pancreas.
Salivary glands: The salivary glands secret saliva, which lubricates the food and initiates the process of chemical digestion in the mouth. The saliva consists of several substances including amylase.
Liver: The bile secreted by the liver helps in the emulsification of fats in the food, when it reaches the duodenum. It is made of bile salts, bilirubin, cholesterol, lecithin, and inorganic salts. Bile flows through the right and left hepatic ducts and reaches the common hepatic duct and finally flows into the small intestine.
Gall bladder: Gall bladder is also known as the biliary vesicle, where bile is stored in concentrated form. Bile flows up the cystic duct and reaches the gall bladder. Excessive bile is stored in the gall bladder and released into the small intestine whenever it is required for the digestion of fat.
Pancreas: The acinar and epithelial cells of pancreas secrete the pancreatic juice. It is a combination of digestive enzymes (lactase, lipase, proteases, amylase, and insulin), water, bicarbonate-buffers, and electrolytes. The pancreatic juice flows through the duct of Wirsung and reaches the common bile duct, where it flows into the small intestine. The pancreatic juice breaks down to metabolize carbohydrates, proteins, and fats, in the small intestine. It also helps in buffering the hydrochloric acid produced in the stomach.
d.What is the purpose of bile salts in food digestion? Where are bile salts produced? Where are they stored? What stimulates their secretion into the gastrointestinal tract?
The function of bile salts in the duodenum is to solubilize ingested fat and fat-soluble vitamins, facilitating their digestion and absorption. It is produced by the liver. It is stored and concentrated in the gallbladder. Intestinal phase signals stimulate the release of bile into the small intestine. Fatty acids in the lumen of the duodenum stimulate endocrine cells to release the hormone called cholecystokinin (CCK). CCK stimulates contractions in the smooth muscle of the gallbladder which ultimately result in the release of bile into small intestine.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.