Digestive system quiz AP Bio
Which of the following statements about the hormone secretin is false? Possible Answers: It inhibits motility in the stomach It is released when acid enters the duodenum, where it is secreted All of these choices are correct It stimulates bicarbonate secretion in the pancreas
Correct answer: All of these choices are correct Explanation: Secretin is a hormone released by the duodenum in response to an influx of acid. The hormone targets the stomach, to reduce the amount of acid that can pass through to the small intestine, and the pancreas, to increase secretion of bicarbonate, which neutralizes the acidity.
which of the following enzymes breaks down starches and carbohydrates? Possible Answers: Trypsin Peptidase Nuclease Lipase Amylase
Correct answer: Amylase Explanation: Amylase is the enzyme that breaks down starches and carbohydrates. There are two types, salivary amylase and pancreatic amylase. Salivary amylase is produced in the mouth by the salivary glands and it is one of the first enzymes that begins the process of food digestion.
removal of the gall bladder from the human body would most likely result in which of the following? Possible Answers: An inability to digest proteins properly An inability to digest carbohydrates properly An inability to digest fats properly An inability to digest starch properly
Correct answer: An inability to digest fats properly Explanation: The gallbladder is found underneath the liver. The gallbladder is the storage place of bile, which helps to emulsify fats. Bile is necessary for the digestive system to break down fat. Removal of the gallbladder can result in fat malabsorption, which can present as loose stool.
What macromolecule is digested first by chemical means? Possible Answers: Nucleic acids Proteins Fats Carbohydrates
Correct answer: Carbohydrates Explanation: Carbohydrates begin their digestion in the mouth, where salivary amylase is produced. Fats are emulsified by bile and digested by lipase in the small intestine. Nucleic acids are also digested in the small intestine by nucleases. Proteins begin their digestion in the stomach, where the low pH of gastric juice begins the breakdown process and pepsin begins to cleave peptide bonds. Protein digestion continues in the small intestine with other protease enzymes.
Which of the following choices incorrectly pairs a digestive enzyme with the digestive tract component in which it is found? Possible Answers: Salivary amylase is found in the mouth Pepsin is found in the stomach All choices successfully pair a digestive enzyme with the digestive tract component in which it is found Cholecystokinin is found in the mouth
Correct answer: Cholecystokinin is found in the mouth Explanation: Cholecystokinin (CCK) is a hormone released by the duodenum to signal and stimulate accessory organs for digestive enzymes. Salivary amylase digests starch in the mouth, while pepsin is used to digest proteins in the stomach.
What is the correct order that a bolus of food will pass through the small intestine? Possible Answers: Jejunum, duodenum, ileum Duodenum, ileum, jejunum Ileum, duodenum, jejunum Duodenum, jejunum, ileum Jejunum, ileum, duodenum
Correct answer: Duodenum, jejunum, ileum Explanation: The correct order that the food will pass as is first the duodenum, then the jejunum and finally the ileum. These are all sections or portions of the small intestine, the organ responsible for the vast majority of absorption of nutrients from food before it is passed on to the large intestine, where water, vitamins, minerals, and any other remaining nutrients are absorbed into the body.
Beginning at the stomach, what is the order of the parts of the small intestine? Possible Answers: Jejunum, ileum, duodenum Duodenum, jejunum, ileum Ileum, duodenum, jejunum Duodenum, ileum, jejunum
Correct answer: Duodenum, jejunum, ileum Explanation: When digested food exits the stomach, it passes through the pyloric sphincter and enters the duodenum, the first region of the small intestine. The duodenum is the introduction point for the pancreatic digestive enzymes, as well as the neutralization of stomach acid. The majority of chemical digestion occurs in the duodenum. The middle region of the small intestine is the jejunum, and the final region is the ileum. These regions are primarily responsible for nutrient absorption and have the largest concentration of microvilli. After passing through the ileum, the digested matter enters the large intestine.
What structure prevents a bolus from entering the trachea? Possible Answers: Tongue Epiglottis Tonsils Pharynx Larynx
Correct answer: Epiglottis Explanation: The epiglottis is a structure that folds forward to cover the trachea when swallowing. It helps to direct food to the esophagus instead of the trachea, preventing liquids and solids from entering the lungs.
In which component of the digestive tract does no digestion occur? Possible Answers: Stomach Small intestine Mouth Esophagus
Correct answer: Esophagus Explanation: The esophagus is responsible for transporting food from the mouth to the stomach via peristalsis, which consists of smooth muscle contractions, but does not help digest the food content in the process. The mouth, stomach, and small intestine, however, all help in the process of food digestion. The mouth introduces enzymes in the saliva, the stomach introduces pepsin, and the small intestine introduces a number of other enzymes for digestion of macromolecules.
A patient is admitted to the hospital with severe abdominal pain. A scan reveals that the gall bladder has multiple stones in it, and one is blocking the cystic duct. Which of the following molecules would be inadequately absorbed during gall bladder obstruction? Possible Answers: All molecule types will be inadequately absorbed Monosaccharides Fatty acids Amino acids
Correct answer: Fatty acids Explanation: The gall bladder is important because of its storage and release of bile during digestion. Bile is important in the emulsification (or breaking up) of nonpolar fats in the aqueous small intestinal fluid. Cystic duct obstruction would result in bile being unable to reach the small intestine, and triglycerides would be unable to be properly emulsified and absorbed.
Which stomach cell type secretes gastrin? Possible Answers: Chief cells G cells Oxyntic cells Parietal cells Goblet cells
Correct answer: G cells Explanation: G cells secrete the hormone gastrin. Gastrin further stimulates stomach acid secretions via parietal (oxyntic) cells. Chief cells secrete pepsinogen, the inactive form of the enzyme pepsin, which degrades proteins. Goblet cells secrete mucous to protect the cells of the stomach from the acid.
Jim's body is able to produce bile salts, but unable to store it in large quantities. As a result, he cannot eat too much fat at once or it can be harmful to his digestive system. The pancreas and large intestine are not involved in bile storage. Which of the following organs is Jim missing? Possible Answers: Pancreas He is not missing any organs. Rather, he has an infected large intestine. Gall bladder Liver
Correct answer: Gall bladder Explanation: The role of the gall bladder is to store bile salts, but it does not produce them. Rather, bile salts are produced by the liver and transported to the gall bladder for storage.
Parietal cells in the stomach secrete which of these? Possible Answers: Mucus Hydrochloric acid Pepsinogen Pepsin Bile salts
Correct answer: Hydrochloric acid Explanation: In the stomach, both hydrochloric acid and pepsinogen are secreted by gastric pits. Parietal cells in these pits secrete hydrochloric acid while chief cells in these pits secrete pepsinogen. Note that pepsinogen is inactive, and gets activated into pepsin via hydrochloric acid.
Which is not a structure of the small intestine? Possible Answers: Ileum Ilium Duodenum Villi Jejunum
Correct answer: Ilium Explanation: Food is converted into a bolus upon swallowing, then into chyme in the stomach. The chyme travels from the stomach into the first part of the small intestine, the duodenum. The chyme then moves through the jejunum, then through the ileum before entering the large intestine. Villi are finger-like projections of the small intestine that increase the surface area of the epithelium to maximize nutrient absorption. The ilium is a part of the hip bone.
What is the purpose of microvilli in the small intestine? Possible Answers: Decrease contracility Increase contractility Increase surface area Decrease surface area
Correct answer: Increase surface area Explanation: Microvilli are found at the microscopic level within the digestive tract to help increase surface area. The increased surface area aids in the absorption of nutrients as they pass through the small intestine. Microvilli allow for folds in the digestive tract, which in turn, increase the amount of area available for nutrient absorption.
How is the zymogen protease activated in the stomach? Possible Answers: It binds to chief cells to become pepsin It is active upon secretion It gets cleaved by trypsin to become catalytically active It reacts with the hydrochloric acid to become pepsin It binds to parietal cells to become pepsin
Correct answer: It reacts with the hydrochloric acid to become pepsin Explanation: To become active, hydrochloric acid in the stomach reacts with pepsinogen to make pepsin.
Which of the following is not a part of the pathway of food through the digestive tract? Possible Answers: Mouth Larynx Esophagus Pharynx Stomach
Correct answer: Larynx Explanation: Food travels in this order through the digestive tract: mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus. The larynx is commonly confused with the pharynx due to their similar names, but it is actually involved in speaking or making sounds. The pharynx splits into the trachea and esophagus. Food and liquids travel down the esophagus, while air travels down the trachea; the larynx is located at the top of the trachea.
Which of the following is a true statement with regard to digestive enzymes? Possible Answers: Amylase breaks down amino acids Proteases only exist in the mouth Most water absorption is performed in the stomach Proteases only exist in the small intestine Lipases digest fats
Correct answer: Lipases digest fats Explanation: Amylase breaks down starch in the mouth and small intestine. Proteases are found in the stomach and small intestine. Water absorption occurs in the intestines (mostly the large intestine). Lipases break down lipids; fats are a type of lipid.
Which of the following is most closely linked to the activation of pepsinogen? Possible Answers: Goblet cell Parietal cell Chief cell G cell
Correct answer: Parietal cell Explanation: Pepsinogen is an inactive enzyme (zymogen) that is released by chief cells into the stomach lumen. In order to be activated, the enzyme must be at a very low pH. This is accomplished by hydrochloric acid, which is released by the parietal cells in response to stimulation by gastrin. Parietal cells are, thus, most closely linked to the activation of pepsinogen. Gastrin is released by G cells. Goblet cells secrete the mucous lining of the stomach.
Which of the following cells in the stomach is necessary for the activation of pepsinogen? Possible Answers: Goblet cells Parietal cells G cells None of these Chief cells
Correct answer: Parietal cells Explanation: Pepsinogen is released by chief cells in the stomach, and is the zymogen form of pepsin. Pepsinogen requires an acidic environment in order to be converted to pepsin. Parietal cells release hydrochloric acid into the stomach lumen, thus activating the enzyme. G cells and goblet cells secrete gastrin and mucous, respectively, into the stomach.
Which enzyme is correctly paired with the macromolecule that it digests? Possible Answers: Amylase catabolizes proteins Peptidase catabolizes lipids Peptidase catabolizes proteins Lipase catabolizes carbohydrates
Correct answer: Peptidase catabolizes proteins Explanation: Amylase is an enzyme found in saliva and the small intestine that breaks starches down into sugars. The correct pairing for amylase would be carbohydrates. Peptidases break peptide bonds, which are what hold amino acids together in proteins. Different peptidases are found in the stomach (pepsin) and the small intestine (trypsin). The correct pairing for peptidase is proteins. Lipase is an enzyme that catalyzes the hydrolysis of triglycerides into free fatty acids in the small intestine. The correct pairing for lipase would be fats or lipids.
Which structure separates the esophagus from the mouth? Possible Answers: Trachea Stomach Pharynx Nasal sinus Pyloric sphincter
Correct answer: Pharynx Explanation: After entering the mouth, food is transferred to the pharynx before entering the esophagus. The pharynx is located immediately above the epiglottis, meaning that both food and air can enter the pharynx. The epiglottis covers the trachea to prevent food from entering, and forces food to travel down the esophagus instead. After food travels through the esophagus it enters the stomach. The pyloric sphincter then separates the stomach from the small intestine.
Which of the following is not a function of the liver? Possible Answers: Detoxes chemicals from the blood Forms urea Produces bile Produces methane
Correct answer: Produces methane Explanation: Methane is produced in the cecum as a result of blind outpocketing, during which E. coli organisms release the gas as a biproduct of digestion. Detoxing chemicals from the blood, forming urea, and producing bile are just three of the functions of the liver.
Which of the given answer choices is not a function of the liver? Possible Answers: Production of glycogen Production of bile Production of insulin Storage of vitamins Detoxification
Correct answer: Production of insulin Explanation: The liver produces bile, which is then stored in the gall bladder. It also stores vitamins and iron, and produces glycogen. The liver is also responsible for detoxification of several metabolites, but it does not produce insulin. Insulin secreted by the pancreas. Other functions of the liver include: synthesis of blood proteins, breakdown of lipids, recycling red blood cells, and glycogen breakdown.
Which of the following does not take place in the small intestine? Possible Answers: Fats are broken down into glycerol by pancreatic lipase Proteins are broken down into amino acids by pepsin Carbohydrates are broken down into simple sugars by pancreatic amylase Fats are broken down into fatty acids by pancreatic lipase Fats are emulsified into smaller particles by bile
Correct answer: Proteins are broken down into amino acids by pepsin Explanation: Complete digestion takes place in the small intestine, but pepsin is present in the stomach where it breaks down proteins to peptides. The pH in the stomach is very low, and pepsin, like all enzymes, has an optimal temperature and pH at which it functions best. For pepsin, this pH happens to be very low. The other enzymes mentioned that function in the small intestine have optimal pH's close to the pH of the small intestine (which is slightly alkaline due to the pancreas secreting bicarbonate).
What is the major enzyme in saliva that acts on carbohydrates? Possible Answers: Lingual lipase Salivary trypsin Lingual pepsin Salivary amylase Lingual amylase
Correct answer: Salivary amylase Explanation: Salivary amylase in the mouth targets large starch molecules and begins the digestion process to a monosaccharide (i.e. glucose). Salivary amylase secretion is stimulated by the recognition of starch on sweet taste receptors, and is carried out by the salivary glands (parotid, submandibular, and sublingual).
Which of the following statements about the pancreas is incorrect? Possible Answers: The pancreas secretes bicarbonate to neutralize chyme The pancreas secretes hydrolytic enzymes through the pancreatic duct and into the small intestine The pancreas is the body's main site of glycogen storage The pancreas secretes the hormones insulin and glucagon
Correct answer: The pancreas is the body's main site of glycogen storage Explanation: Glycogen is stored primarily in cells of the liver and muscles. The pancreas is responsible for secreting hydrolytic enzymes into the small intestine via the pancreatic duct. Along with these digestive enzymes the pancreas releases bicarbonate, which reacts in an acid-base reaction with acidic stomach chyme to pervent it from damaging the intestine. The pancreas also releases insulin and glucagon, among other hormones.
Why are villi found in the small intestine, but not in the stomach? Possible Answers: The villi allow multiple areas where digestive enzymes can be released by the small intestine. The stomach does not release digestive enzymes. The small intestine uses villi to adhere to the food particles entering from the stomach, while the stomach has no need for such adhesion. The villi act in a cilia-like motion and move food down the small intestine. Movement in the stomach is generated by smooth muscle contractions. The small intestine uses the villi to increase its surface area and facilitate absorption. Absorption does not occur in the stomach.
Correct answer: The small intestine uses the villi to increase its surface area and facilitate absorption. Absorption does not occur in the stomach. Explanation: The villi are helpful in increasing the surface area of the small intestine. This greatly increases the absorptive capabilities of the small intestine. The stomach has no villi, and does not contribute to absorption of macromolecules.
In which region of the upper digestive tract does food transition into chyme? Possible Answers: The stomach The sublingual salivary glands The liver The mouth The esophagus
Correct answer: The stomach Explanation: Chyme is formed during the initial breakdown of food. Food is turned into chyme in the stomach due to the combination of smooth muscle contractions and the chemical action of hydrochloric acid. These processes serve to digest the food both mechanically and chemically.
n the stomach, the __________ cell secretes __________. Possible Answers: parietal cell . . . hydrochloric acid parietal cell . . . pepsinogen chief cell . . . pepsin chief cell . . . hydrochloric acid chief cell . . . pepsinogen
Correct answer: chief cell . . . pepsinogen Explanation: The chief cells of the stomach secrete the proteolytic zymogen pepsinogen. This zymogen then becomes activated as pepsin in the stomach.
he __________ cell of the stomach are responsible for secreting the __________ that lines the stomach and protects its epithelial cells from its highly acid contents. Possible Answers: chief . . . bile pariental . . . lipase goblet . . . bile parietal . . . mucous goblet . . . mucous
Correct answer: goblet . . . mucous Explanation: The surface mucous cells secrete mucous, which covers the cells that line the stomach. Without proper mucous secretion, the stomach can become damaged or even perforated.
The high concentration of __________ present in the stomach activates pepsinogen, allowing it to become active pepsin. Possible Answers: undigested food ATP saliva bile hydrochloric acid
Correct answer: hydrochloric acid Explanation: Hydrochloric acid, produced by the parietal cells of the stomach, activates the zymogen pepsinogen.
Bile is produced in the __________, stored in the __________, and released into the __________. Possible Answers: liver . . . gallbladder . . . small intestine liver . . . gallbladder . . . large intestine gallbladder . . . gallbladder . . . small intestine kidneys . . . gallbladder . . . small intestine
Correct answer: liver . . . gallbladder . . . small intestine Explanation: The liver is responsible for synthesizing bile salts; these salts are transferred into the gallbladder as bile. The gallbladder stores bile, which it then secretes into the small intestine. Bile contributes to digestion by breaking up large fat globules, a process known as emulsification. Fats are insoluble in water, so emulsification provides pancreatic lipase with more surface area on which to act. Neither the spleen nor the large intestine are relevant answers to this sentence. The large intestine helps remove undigested waste from the body, absorbs water from waste, and produces/absorbs vitamins (due to colonies of beneficial bacteria that live in the large intestine). The spleen is an organ responsible for filtering the blood and housing white blood cells; it is not involved in digestion.
Bile salts emulsify dietary fats by breaking them down into smaller clusters and creating a molecule called a __________. Possible Answers: bolus chylomicron globule micelle cluster
Correct answer: micelle Explanation: Bile salts surround fat droplets in order to create micelles. These micelles are more accessible to the enzymes that have the ability to break them down further. Chylomicrons are lipoproteins that are important in transport and metabolism of lipids.
The __________ cell secretes __________ in order to reduce the pH of the stomach to increase food digestion. Possible Answers: chief . . . hydrochloric acid parietal . . . bile parietal . . . hydrofluoric acid chief . . . carbonic acid parietal . . . hydrochloric acid
Correct answer: parietal . . . hydrochloric acid Explanation: The parietal cells of the stomach begin secreting hydrochloric acid even upon the smell of food (before consumption takes place) in order to begin the digestion process. These cells are common targets of antacid medications to reduce acid reflux.
The esophagus is able to swallow liquids upside down, proving that swallowing is a process that does not depend on gravity. What is the name of this process? Possible Answers: esophageal emulsification flatulation peristalsis denaturation salivation
Correct answer: peristalsis Explanation: Peristalsis is the correct answer here. Peristalsis is the process of muscles contracting and relaxing in order to facilitate movement.
Enzymes such as trypsin and chymotrypsin in the small intestine break __________ into __________. Possible Answers: proteins . . . amino acids carbohydrates . . . diasaccharides carbohydrates . . . monosaccharides nucleic acids . . . nucleotides fats . . . lipids
Correct answer: proteins . . . amino acids Explanation: Trypsin and chymotrypsin belong to a family of enzymes that are "proteolytic". This means that they target proteins and break them down into their building blocks called amino acids
The parietal cells of the stomach secrete acid through the use of a __________. Possible Answers: ATP synthase proton pump sodium-potassium pump None of these hydrochloric acid channel
Correct answer: proton pump Explanation: The parietal cells use a proton pump to release hydrogen ions into the stomach in the form of hydrochloric acid. This pump is the target of PPI (proton pump inhibitor) medications that work to reduce stomach acid.
One of the functions of the liver is __________. Possible Answers: to physically digest food to act as the main storage center for bile to secrete epinephrine and norepinephrine to produce insulin in its specialized beta cells to produce bile, triglycerides, and cholesterol
Correct answer: to produce bile, triglycerides, and cholesterol Explanation: The liver has a large number of functions, including metabolizing toxins, synthesizing proteins, and storing glucose in the form of glycogen. The only answer choice that describes liver functions is the production of bile, triglycerides, and cholesterol. The pancreas produces insulin from beta cells, the gall bladder stores bile, and the adrenal medulla secretes epinephrine and norepinephrine. Physical digestion takes place mainly in the mouth and stomach, not the liver.
Through which sphincter will a bolus pass to enter the stomach? Is this under control of the parasympathetic of sympathetic division of the autonomic nervous system? Possible Answers: Urethral sphincter, which is under control of the sympathetic nervous system Gastroesophageal sphincter, which is under control of the sympathetic nervous system Pyloric sphincter, which is under control of the sympathetic nervous system Gastroesophageal sphincter, which is under control of the parasympathetic nervous system Pyloric sphincter, which is under control of the parasympathetic nervous system
Gastroesophageal sphincter, which is under control of the parasympathetic nervous system Explanation: The contraction and relaxation of a layer of smooth muscle at the junction of the esophagus (-esophageal) and the stomach (gastro-) allows for the bolus to pass into the stomach upon relaxation, and by contraction keeps the bolus, acid, and other stomach contents from regurgitating into the esophagus from the stomach. This sphincter is under vagus nerve control, thus, the parasympathetic nervous system.
Which compound is correctly matched to the type of cell that produces it? Possible Answers: Goblet cells secrete hydrochloric acid Parietal cells secrete pepsinogen Parietal cells secrete mucous Chief cells secrete pepsin Chief cells secrete pepsinogen
The stomach contains several cell types, each with a specific mechanism of action. Chief cells produce pepsinogen, which is converted to pepsin by hydrochloric acid in the stomach. Parietal cells produce hydrochloric acid, allowing this conversion. Goblet cells produce the mucous lining of the stomach that protects the stomach epithelium from damage from the acidic environment of the gastric lumen
Which of the following functions is NOT accomplished by the liver? Possible Answers: Glycogen storage Blood filtration Antibody creation Vitamin storage
correct answer: Antibody creation Explanation: The liver is a very important organ with many interrelated functions, however, the liver is not responsible for the creation of antibodies. This is done by plasma cells, a key cell type in the immune system.
Which of the following statements about cholecystokinin (CCK) and gastrin is true? Possible Answers: Both hormones target the stomach, but for different functions Both hormones target the pancreas, but for different functions Both hormones are secreted only by the duodenum Both hormones target the gall bladder to release bile
correct answer: Both hormones target the stomach, but for different functions Explanation: Cholecystokini (CCK) targets the stomach to inhibit motility, while gastrin targets the stomach to increase motility. Gastrin is secreted by the duodenum and the stomach, but targets only the stomach. CCK, however, targets the stomach, pancreas, and gall bladder.
Amylase is a digestive enzyme responsible for breaking down which macromolecules found in food? Possible Answers: Proteins Lipids Carbohydrates None of these Nucleic acids
correct answer: Carbohydrates Explanation: The correct answer is carbohydrates because amylase is the enzyme that is able to break these macromolecules down into smaller parts. There are two kinds of amylase found in the body, salivary amylase in the mouth and pancreatic amylase in the pancreas. Both of these are involved in the breakdown of carbohydrates in digestion.
Which of the following segments of the digestive system has the primary job of digesting food? Possible Answers: Ileum Jejunum Duodenum Colon
correct answer: Duodenum Explanation: The duodenum, in the small intestine, is a site of protein, carbohydrate, and fat digestion. The jejunum is a site of protein and fat absorption. The ileum is a site of salt, vitamin, and excess molecule absorbtion. The colon is a segment of the large intestine for water and ion absortion. Each of these work to absorb different molecules, but do not significantly contribute to their digestion.
Which digestive system organ secretes enzymes vital for lipid digestive, and where are these enzymes introduced into the digestive tract? Possible Answers: Enzymes from the liver are introduced into the stomach Enzymes from the pancreas are introduced into the duodenum Enzymes from the pancreas are introduced into the stomach Enzymes from the liver are introduced into the colon
correct answer: Enzymes from the pancreas are introduced into the duodenum Explanation: Lipase is synthesized and secreted from the pancreas into the duodenum of the small intestine. Lipase plays a key role in the digestion of lipids.
Which organ stores the compound responsible for emulsifying lipids during digestion? Possible Answers: Liver Pancreas Gall bladder Small intestine
correct answer: Gall bladder Explanation: Fats are generally composed of nonpolar lipids, making them hydrophobic and insoluble. In order to digest fats, they must be grouped together to increase their surface area and allow for enzyme interaction, digestion, and absorption. Fat emulsification is the process of increasing the surface area of fats in the small intestine by grouping them into small clusters. This is the responsibility of bile, a liquid created by the liver and stored in the gallbladder. Actual digestion of the fats is then accomplished by lipase, an enzyme from the pancreas. Digested lipids are then transported into the lacteals of the microvilli for transportation through the lymphatic system before entering the blood.
Where is bile stored when digestion is not occurring? Possible Answers: Adrenal glands Appendix Spleen Gall bladder Kidney
correct answer: Gall bladder Explanation: The liver produces bile, which travels down the bile duct to be released into the small intestine, specifically the duodenum. When the duct is not open, bile backs up and gets stored in the gall bladder. Once the duct is open, when the small intestine senses the presence of food, the gall bladder will release the bile to emulsify fats during digestion.
Which of the following enzymes does NOT directly contribute to protein digestion? Possible Answers: Chymotrypsin Gastrin Pepsin Trypsin
correct answer: Gastrin Explanation: Gastrin is secreted in the stomach, and stimulates the secretion of hydrochloric acid by parietal cells. The other three enzymes directly aid in the digestion of proteins. Trypsin and chymotrypsin are released from the pancreas into the duodenum, and pepsin digests proteins located in the stomach. Each of these has different cleavange targets within protein sequences and can be used as a restriction enzyme in experimental procedures.
Bile salts are amphipathic and essential for fat absorption. Which of the following nutrients will be difficult to absorb in a patient with an inability to secrete bile salts into the stomach? I. Vitamin A II. Vitamin B III. Vitamin C Possible Answers: I and II II only I and III All of these I only
correct answer: I only Explanation: Bile salt emulsifies fat into chylomicrons to allow for absorption. Of the choices, only vitamin A is fat-soluble. Vitamins B and C are both water-soluble.
Which of the following does NOT play a role in the emulsification of dietary lipids? Possible Answers: Phospholipids Small intestine motility Bile salts Lipase
correct answer: Lipase Explanation: Both bile salts and phospholipids are excreted from the bile duct into the upper small intestine (duodenum) to emulsify lipids. They are both amphipathic molecules, which means they have non-polar/lipophilic ends that can bind to lipids and polar/hydrophilic ends that can bind to water, thus emulsifying the lipids that they contact. As these compounds are excreted from a single duct, small intestine motility allows them to mix with the contents of the small intestine and emulsify more lipids than they would be able to in a still environment. Small intestine motility also helps to break up large globules of dietary fat. Once emulsified, dietary fat can be broken down by lipase, but lipase itself does not enhance emulsification.
Which of the following is not secreted by the pancreas into the duodenum? Possible Answers: Lipases Bile salts Pepsin Trypsin Bicarbonate
correct answer: Pepsin Explanation: Pepsin is a protein degrading enzyme that is released by the stomach. All the other choices are released by the pancreas into the duodenum.
Which enzyme operates at the lowest pH? Possible Answers: Lipase Amylase Pepsin Carboxypeptidase Trypsin
correct answer: Pepsin Explanation: Pepsin is the only enzyme out of the given choices that functions in the stomach, where the pH is very low (acidic). Trypsin, carboxypeptidase, and lipase all function within the small intestine, where the pH is usually more basic to neutralize the pH of chyme as food is digested. Amylase is found in saliva and functions in the mouth, where pH is about neutral.
Ammonia is a byproduct of digestive absorption. It is converted to urea by the liver and expelled in the urine. Which macromolecule is responsible for the presence of the ammonia byproduct during digestion and absorption? Possible Answers: Carbohydrates All macromolecules create an ammonia byproduct Proteins Fatty acids
correct answer: Proteins Explanation: In order to answer this question, visualize the macromolecules as their monomers. The chemical formula for ammonia is NH3, so the monomer will need to include nitrogen. Carbohydrates are chains of monosaccharides and are only composed of carbon, hydrogen, and oxygen. Fatty acids are nonpolar molecules, and are composed of only carbon and hydrogen. Proteins are composed of amino acid monomers. Amino acids have an amino terminus, which includes a nitrogen atom. As a result, only proteins have the nitrogen atom which can be used in the byproduct of ammonia.
Nutrient-rich blood moves from the small intestine to the liver via which of the following structures? Possible Answers: The hepatic portal system The pancreatic duct The pulmonary circuit Lacteal vessels
correct answer: The hepatic portal system Explanation: The hepatic portal system involves the capillaries of the small intestine and capillaries of the liver. A portal system refers to two different capillary beds, connected by arterioles, that both receive blood before it returns to the heart for reoxygenation. The prefix "hepa-" refers to the liver. The pancreatic duct transfers digestive enzymes from the pancreas into the lumen of the small intestine. Lacteal vessels receive fats from the small intestine and carry them into the lymphatic system. The pulmonary circuit refers to the region of the circulatory system that carries blood from the right ventricle to the lungs, and back to the left atrium.
Which organ secretes proteolytic zymogens (inactive enzymes) that are present in small intestine? Possible Answers: The small intestine The pancreas The stomach The large intestine The liver
correct answer: The pancreas Explanation: The pancreas is responsible for secreting proteolytic zymogens, such as trypsinogen, into the small intestine. This is triggered by the presence of undigested food (chyme) in the duodenum.
The __________ synthesizes bile while the __________ stores and secretes it into the small intestine. Possible Answers: stomach . . . gallbladder liver . . . stomach small intestine . . . pancreas liver . . . gallbladder pancreas . . . liver
correct answer: liver . . . gallbladder Explanation: Bile is synthesized in the liver and secreted by the gallbladder into the small intestine upon the appearance of acidic chyme in the duodenum. Bile contains salts that emulsify (solubilize) fats, which is a necessary step in their digestion. If the gallbladder is removed, the liver can take over both roles.
Bile salts make fat droplets more accessible to the enzyme __________. Possible Answers: trypsin chymotrypsin pepsin lingual lipase pancreatic lipase
correct answer: pancreatic lipase Explanation: Once large fat clusters are broken down by bile salts to become smaller micelles, pancreatic lipase has more surface area to access fats. The enzymes are able to reach the fat droplet through the gaps between bile salts. Fats are not emulsified by bile yet in the mouth, so lingual lipase acts upstream of bile to hydrolize long chain hydrocarbons. The other answer choices are proteases.
Which of the following enzymes becomes activated in a low pH environment? Possible Answers: Trypsinogen Lysozyme Chymotrypsinogen Pepsinogen Gastrin
orrect answer: Pepsinogen Explanation: The only one of the enzymes listed that becomes activated in the presence of an acidic (low pH) environment is pepsinogen. When activated, pepsinogen forms into pepsin which occurs in the stomach because of the HCl (hydrochloric acid) present. Enzymes and/or hormones that have the suffix -ogen, or the prefix pro- are known as zymogens or prohormones, which are not active. Different environments/molecules activate these enzymes and proteins. This method of activation allows for more rapid usage, rather than having to synthesize these molecules from scratch when they are needed.
Zymogens are excreted in the digestive system in order to __________. Possible Answers: Be more active than enzymes and break down food quickly Be more resilient to the low pH of the stomach To save energy by producing an effective, but less costly enzyme Be more specific to digestion Prevent accidental digestion of the body's proteins rather than dietary protein
orrect answer: Prevent accidental digestion of the body's proteins rather than dietary protein Explanation: Zymogens are inactive forms of enzymes that are secreted in order to prevent the accidental digestion of the body's important proteins (i.e. other enzymes, structural proteins). These zymogens are then activated through further processing in the compartments in which they are meant to work.
