After ingestion, the first type of macromolecule to be worked on by enzymes in the mouth is: - protein - carbohydrate - fat - nucleic acids Which of the following statements about the digestive system is true? - All foods begin their enzymatic digestion in the mouth - After leaving the oral cavity, the bolus enters the esophagus - The epiglottis prevents food from entering the trachea - Enzyme production continues in the stomach - The esophagus leads to the stomach Which of the following statements about pepsin is true? Pepsin: - is manufactured by the stomach - helps stabilize fat-water emulsions - splits maltose into monosaccharides - begins the hydrolysis of proteins in the stomach - is denatured and rendered inactive in solutions with low pH Without functioning parietal cells, an individual would: - not be able to initiate protein digestion in the stomach - not be able to initiate mechanical digestion in the stomach - only be able to digest fat in the stomach - not be able to produce pepsinogen - not be able to initiate digestion in the small intestine Enzymatic hydrolysis of all of the macromolecules to their simple forms occurs in the: - small intestine - large intestine - stomach - liver Most nutrients are absorbed across the epithelium of the: - villi of the small intestine - rugae of the stomach - mucosal layer of the esophagus - mucosa of the large intestine A structure that does not manufacture any digestive substances is the: - duodenum - pancreas - salivary gland - gallbladder Which of the following statements about bile salts is true? - Bile salts are not enzymes - Bile salts are made by the liver - Bile salts emulsify fats in the duodenum - Bile salts increase the efficiency of pepsin action - Bile salts are normally an ingredient of gastric juice Which structure is home to large amounts of E. coli that produces Vitamin K as a by-product of their metabolism? - esophagus - stomach - small intestines - large intestines How does the digestion and absorption of fat differ from that of carbohydrates? - The process of fat does not require any digestive enzymes whereas the processing of carbohydrates does - Fat absorption occurs in the small intestine whereas carbohydrates are absorbed from the small intestine - Carbohydrates need to be emulsified before they are digested whereas fats do not - Most absorbed fat first enters the lacteal whereas carbohydrates directly enter the blood
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After ingestion, the first type of macromolecule to be worked on by enzymes in the mouth is: carbohydrate. This is because the enzyme amylase, which breaks down carbohydrates, is present in saliva. Show more…
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A. The stomach is a muscular sac in the abdomen that receives food, stores it, breaks it up, and begins digestion to produce chyme. 1. The stomach is divided into four regions. a. Cardiac region b. Fundus region c. Body region d. Pyloric region 2. Between the esophagus and duodenum, the stomach has two margins called the lesser and greater curvatures. B. Microscopic anatomy shows that the stomach wall has tissue layers similar to those of the esophagus with some variation. 1. The mucosa is covered with simple columnar epithelium. 2. The gastric mucosa is pocked with depressions called gastric pits lined with columnar epithelium. i. Parietal cells are found mostly in the upper half of the gland and secrete hydrochloric acid, intrinsic factor, and ghrelin. ii. Chief cells, which are the most numerous, are found in the lower half of gastric glands; they secrete pepsinogen and gastric lipase. C. Most digestion and nearly all nutrient absorption occur in the small intestine. 1. The stomach does not absorb significant nutrients but does absorb aspirin and some lipid-soluble drugs. 2. Alcohol is absorbed mainly by the small intestine, so its intoxicating effects are delayed until it reaches the bloodstream. V. The Small Intestine A. Nearly all chemical digestion and nutrient absorption occur in the small intestine, so called because of its small diameter (2.5 cm). B. In terms of gross anatomy, the small intestine: 1. The duodenum constitutes the first, beginning at the pyloric sphincter, arching around the head of the pancreas, and ending at a sharp bend called the duodenojejunal flexure. a. Here stomach acid is neutralized, fats are emulsified by bile, pepsin is inactivated by elevated pH, and pancreatic enzymes take over chemical digestion. 2. The jejunum is the first 40% of the small intestine beyond the duodenum (1.0 to 1.7 m in a living person). a. Most digestion and nutrient absorption occur here. 3. The ileum forms the last 60% of the postduodenal small intestine. 4. The end of the small intestine is the ileocecal valve, where the ileum joins the cecum of the large intestine.
Sri K.
Why do the cells of the digestive system secrete proteolytic enzymes, such as pepsin, in their inactive forms? A) These proteolytic enzymes, in active form, would digest the very tissues that synthesize them. B) By secreting inactive enzymes, the catalytic activity of the enzymes is maintained for a longer time. C) The stomach is too acidic to maintain these enzymes in their active form. D) Inactive pepsin and trypsin are more easily transported across the cell membrane Over-the-counter medications for acid reflux or heartburn block the production of stomach acid. Which of the following cells are directly affected by this medication? A) goblet cells B) chief cells C) parietal cells D) smooth muscle cells The digestion of fats differs from that of carbohydrates in that ________. A) Fat digestion needs bile from the liver while carbohydrate does not B) Carbohydrates need to be emulsified before they can be digested, whereas fats do not C) Fat digestion occur in large intestine D) Fats, but not carbohydrates, are digested by bacteria before absorption Constipation can result from the consumption of a substance that ________. A) promotes water reabsorption in the large intestine B) speeds up movement of material in the large intestine C) decreases water reabsorption in the small intestine D) stimulates peristalsis If you place a small piece of a cracker on your tongue, what would you expect to happen? A) The vitamins in the cracker are immediately absorbed. B) Degradation of the starch from the cracker into glucose. C) The proteins in the cracker begin to be digested. D) The flavor becomes less noticeable because the sugars are digested.
Josee P.
3. Carbohydrates A. Carbohydrate digestion begins in the oral cavity. Name the enzyme that initiates carbohydrate digestion. Name the 3 sets of organs that secrete this enzyme. B. Describe how carbohydrates are chemically digested in the small intestine. Include a discussion of brush border enzymes. C. Does the pancreas release any enzymes which chemically digest carbohydrates? If yes, name it (them). How does pancreatic juice enter the small intestine? D. Fiber (AKA cellulose in plant cell walls) is not digestible. Why not? Despite not being digestible, fiber is beneficial to our health. Why? 4. Proteins A. Where are proteins first digested chemically? What enzyme initiates protein digestion? B. Does the pancreas release any enzymes that chemically digest proteins? If yes, name it (them). C. Describe 3 ways in which the body uses these protein subunits. 5. Fats A. Chemical digestion of lipids occurs primarily in the small intestine. Before enzymes can break down fats like triglycerides (the most common type of fat in our foods), they must undergo emulsification. Describe the process of emulsification. Name the substance which performs this job. Name the organ that synthesizes this substance. Name the organ which stores and concentrates this substance. How does this substance get into the duodenum of the small intestine? B. After fats are emulsified, they are chemically digested. What is the general name for enzymes which digest fats? Name all of the organs which synthesize and secrete this enzyme into the digestive tract. C. Cholesterol is a type of fat. Why is it important to have some cholesterol in our diets? Why is it important not to have too much cholesterol in our diets? 6. Waste Production A. The large intestine AKA colon is the digestive organ which produces feces. Starting with the cecum and ending with the anus, name ALL parts of the large intestine in order. B. How does the large intestine convert liquid waste from the small intestine into solid waste to be eliminated from the body? C. Name 5 components of fecal matter. NOTE that the small intestine absorbs ALL of the digestible carbohydrates, proteins, and fats in our diets; thus, these nutrients must NOT be in your list.
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