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The Alimentary Canal: Digestion and Absorption

MULTIPLE CHOICE

     1.   Each of the following is a portion of the alimentary canal except one. Which one is the exception?

a.
Oral cavity
b.
Pharynx
c.
Larynx
d.
Esophagus
e.
Small intestine

ANS:  C

The larynx is not a portion of the alimentary canal. This tubular structure is approximately 30 feet long and comprises all the body parts through which food passes.

REF:   p. 51

     2.   The small intestine is comprised of the cecum, colon, and rectum. The large intestine includes the duodenum, jejunum, and ileum.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

The statements are reversed. The small intestine is comprised of the duodenum, jejunum, and ileum. The large intestine includes the cecum, colon, and rectum.

REF:   p. 51

     3.   Mechanical aspects of digestion include chewing and hypergeusia. Mechanical actions involve peristalsis, voluntary waves of contraction traveling the whole length of the alimentary tract.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

Mechanical aspects of digestion include chewing and peristalsis. Peristalsis is a series of involuntary rhythmic waves of contraction traveling the whole length of the alimentary tract. Note that hypergeusia is a condition where the sense of taste is heightened.

REF:   p. 51

     4.   Each of the following is true of enzymes except one. Which one is the exception?

a.
Enzymes are complex proteins that are very specific.
b.
Enzymes regulate metabolic reactions so that they proceed slowly and thoroughly.
c.
Enzymatic reactions require a substrate.
d.
Only small amounts of an enzyme is needed to complete a reaction.

ANS:  B

Enzymes enable metabolic reactions to proceed at a faster rate without being exhausted. Enzymes function similar to keys: they are highly specific and function on only one substrate, similar to a key fitting a particular lock. When the reaction is completed, the complex separates, releasing new chemical compounds and the enzyme.

REF:   p. 51

     5.   Loss of smell results in a condition that limits capacity to detect flavor of food and beverages called:

a.
hypergeusia.
b.
dysgeusia.
c.
anosmia.
d.
phantom taste.
e.
peristalsis.

ANS:  C

Anosmia, or loss of smell, results in limited capacity to detect flavor of food and beverage. Upper respiratory infections, nasal or sinus problems, and neurological disorders can cause anosmia. Hypergeusia is heightened taste acuity. Dysgeusia is persistent, abnormal distortion of taste. Phantom taste is dysgeusia without identifiable taste stimuli. Peristalsis is a mechanical action involved in digestion. It involves involuntary rhythmic waves of contraction in the alimentary tract.

REF:   p. 54

     6.   Gluten sensitivity, an allergic condition, is an example of a systemic condition. Gluten sensitive patients develop impairment of the small intestine.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

Gluten sensitivity is an example of a systemic condition because it qualifies as a disease or disorder that affects the whole body, but it is not an allergic condition. Gluten-sensitive patients can develop gastrointestinal symptoms, but the small intestine is not impaired. Gluten is a protein composite found in foods processed from wheat.

REF:   p. 54 | p. 62

     7.   During peristalsis, doorlike mechanisms called valves or sphincter muscles perform all of the following functions except one. Which one is the exception?

a.
Retain food in each segment until mechanical actions is complete.
b.
Allow measured amount of food to pass to next segment.
c.
Synthesize dietary enzymes necessary for chemical digestion.
d.
Prevent food from “backing up” into the preceding area.

ANS:  C

Valves or sphincter muscles within the alimentary tract are strictly involved in mechanical aspects of digestion and do not synthesize dietary enzymes. An example of valvular peristaltic action is the small amounts of chyme that are released from the stomach through the pyloric sphincter to allow for adequate digestion and absorption in the small intestine. Regulation of these valves is complex, involving muscular function and different pressures on each side of the valve.

REF:   p. 51

     8.   Food-drug interactions have the potential to cause nutritional problems. For example, consuming milk or milk products while taking amoxicillin decreases the amount of antibiotic and calcium available to the body.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  C

Amoxicillin undoubtedly has other food-drug interactions, but it is tetracycline that interacts with milk and milk products. The result of this interaction is that lowered amounts of tetracycline and calcium are available to the body.

REF:   p. 52 | Dental Considerations

     9.   The use of over-the-counter enzyme tablets might not be beneficial to patients because the enzymes within the product are digested before they can be used.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  A

Prescription enzymes are more likely to have protective features which prevent the active ingredient from being digested prior to the point at which it can be used. For example, prescription pancreatic enzymes have a special enteric coating preventing the enzyme from exposure to gastric juices. An example of an OTC product that has such a protective feature is lactase which is effective for lactose-intolerant because it is either added to or taken with lactose-containing foods.

REF:   p. 52 | Nutritional Directions

   10.   Taste buds, receptors of taste located in the oral cavity, play an important role in the digestive system. Food choices are influenced by gustatory or visual sensations, taste, and smell.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  C

Gustatory refers to taste, which is one of the three sensory perceptions that influence food choices. The remaining two are sight and smell. As food is chewed, gustatory receptors are exposed to chemicals dissolved in saliva.

REF:   p. 53

   11.   Each of the following descriptions of taste papillae is true except one. Which one is the exception?

a.
A taste bud consists of 30 to 100 papillae.
b.
Taste papillae appear on the tongue as large red spots or small bumps.
c.
Taste papillae are most numerous on the dorsal epithelium of the tongue.
d.
Taste papillae replace themselves every 3 to 10 days.

ANS:  B

Taste papillae appear on the tongue as little red dots, or raised bumps. They are most numerous on the dorsal surface of the tongue, which is the top surface. Disease, drugs, nutritional status, radiation, and age can affect taste papillae.

REF:   p. 53

   12.   It is not uncommon for an elderly patient to state that food “just doesn’t taste good,” because the impairment of the olfactory nerves is prevalent in older adults.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  A

Aromas stimulate olfactory nerves, which are receptors for smell. Prevalence of impairment of olfactory nerves is high in older adults, with the problem increasing with age.

REF:   p. 54

   13.   Gustatory and olfactory disorders can result in deterioration of a patient’s general condition or nutritional status. Potentially adverse compensatory habits can contribute to dental caries and systemic conditions.

a.
Both the statement and the reason are correct but are not related.
b.
The statement is correct, but the reason is not correct.
c.
The statement is not correct, but the reason is correct.
d.
Neither the statement nor the reason is correct.

ANS:  A

It is not unusual for patients with impaired taste (gustatory) and smell (olfactory) senses to decline in health. In an effort to enjoy meals, many patients make compensatory changes such as adding of sugar and other sweeteners. These substances have detrimental health consequences, including dental caries and blood glucose disturbances. The addition of salt, another compensatory measure to improve the eating experience, negatively affects cardiovascular health.

REF:   p. 53 | p. 54

   14.   Each of the following is a function of saliva except one. Which one is the exception?

a.
Saliva is essential to gustatory sensations.
b.
Saliva lubricates oral tissues.
c.
Saliva provides antibacterial action.
d.
Saliva buffers bacterial acids.
e.
Saliva replaces calcium and phosphate in demineralized tooth surfaces with collagen.

ANS:  E

Saliva restores or returns calcium, phosphates, and other minerals into surfaces of teeth that have been damaged by caries, erosion, or abrasion. Saliva is supersaturated with calcium phosphates.

REF:   p. 55

   15.   Saliva is supersaturated with bacterial by-products that allow demineralized areas of hydroxyapatite in enamel to be remineralized. Demineralization occurs when calcium, phosphate, and other minerals migrate from the enamel surface into the dentin.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

Saliva is supersaturated with calcium phosphates that allow demineralized areas of hydroxyapatite in enamel to be remineralized. Remineralization is defined as the restoration or return of calcium phosphates and other minerals into damaged tooth surfaces. Demineralization occurs when calcium, phosphate, and other minerals are lost from tooth enamel, causing tooth enamel to dissolve.

REF:   p. 55

   16.   Demineralization is a result of acids produced by fermentable carbohydrates combining with proteins to form prebiotics. Demineralization is caused by a lack of calcium intake or a calcium deficiency.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

Demineralization is a result of acids produced by fermentable carbohydrates combining with acidogenic bacteria. It is not caused by lack of calcium intake or a calcium deficiency. Note that prebiotics are nondigestible food ingredients that have beneficial effects within the large intestine and colon.

REF:   p. 55

   17.   Hydrolysis of a starch begins with which enzyme?

a.
Salivary amylase
b.
Pepsin
c.
Pancreatic amylase
d.
Sucrase

ANS:  A

Some chemical action or hydrolysis of nutrients begins in the mouth. Salivary amylase initiates starch digestion. If a carbohydrate, such as a cracker, is chewed and held in the mouth for a few seconds, it will begin to taste sweet. This denotes that some of the starch is being hydrolyzed to dextrin and maltose. Note that the name for many enzymes is derived from the name of its substrate, with the suffix -ase. Sucrase is the enzyme that hydrolyzes sucrose.

REF:   p. 55

   18.   Digestion is accomplished solely through chemical activities on food because peristalsis permits blending of foodstuffs with digestive secretions.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  D

Digestion involves two basic types of action on food: mechanical and chemical. Mechanical actions include chewing and peristalsis, both of which break up and mix foods. The mechanical actions permit better blending of foodstuffs with digestion secretions.

REF:   p. 51

   19.   The accessory organs include the large and small intestine. The role of accessory organs is to store foodstuffs during the digestive process.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

The accessory organs are the salivary gland, liver, gallbladder, and pancreas. They provide secretions essential for digestion and absorption.

REF:   p. 51

   20.   The maxilla and mandible need the forces of chewing to prevent calcium absorption. Chewing firm food helps to maintain a proper balance between bone breakdown and new bone formation within the alveolar process.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  D

The maxilla and mandible need chewing forces to prevent the resorption of calcium. Resorption breaks down a substance; absorption integrates a substance into the body. Calcium absorption is a desired process, whereas calcium resorption is not. The alveolar process is the crest of the maxilla and mandible that serves as the bony investment for the teeth.

REF:   p. 55

   21.   Missing teeth increase the potential for food obstruction in the airway, because an inability to masticate food can result in larger chunks of food being swallowed.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  A

The act of chewing reduces food particle size. An inability to masticate food adequately can result in large chunks of food being swallowed, which increases the potential for food obstruction in the airway. Loss of even one permanent molar can decrease masticatory efficiency, which is defined as how well a patient prepares food for swallowing.

REF:   p. 56

   22.   Masticatory efficiency refers to enhancement of gustatory effects. Even after a patient becomes fully adjusted to well-fitted dentures, masticatory efficiency is reduced compared with that of patients with their natural teeth.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  D

Masticatory efficiency refers to how well a patient prepares food for swallowing. Gustatory sensations, more commonly known as the sense of smell, are intricately involved with appetite, but this is not definitive of masticatory efficiency. When masticatory efficiency declines, people frequently choose foods that require less chewing or they use techniques to soften foods, such as stewing meats, steaming vegetables, or dunking cookies in fluids.

REF:   p. 56

   23.   Each of the following is true of swallowing and processing food except one. Which one is the exception?

a.
The swallowing reflex moves a bolus into the esophagus.
b.
A bolus is a mass of food.
c.
The bolus is transported to the stomach by osmosis and gravity.
d.
The bolus penetrates the diaphragm through the esophageal hiatus.
e.
The lower esophageal sphincter relaxes to permit food into the stomach.

ANS:  C

The bolus is transported to the stomach by peristalsis and gravity. Peristalsis is a series of contractile waves that mechanically move the bolus through the alimentary tract. Note that osmosis is the passage of water through a semipermeable membrane to equalize osmotic pressure. This process involves ionic control of movement of water (fluids) across membranes.

REF:   p. 56

   24.   The lower esophageal sphincter is a bony structure located within the stomach. It relaxes to permit food to move within the stomach on its way to the intestines.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

The lower esophageal sphincter comprises a group of strong circular muscle fibers located just above the stomach. The lower esophageal sphincter relaxes to permit food into the stomach.

REF:   p. 56

   25.   In a well-functioning alimentary tract, stomach contents do not “back wash” into the esophagus, because the pyloric sphincter prevents foodstuff from seeping back into the esophagus.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  C

When all components are functioning correctly, the lower esophageal sphincter prevents backwash of foodstuff (chyme). The pyloric sphincter performs a similar task in a different location. It releases small amounts of chyme from the stomach into the small intestine for digestion and absorption.

REF:   p. 57

   26.   A patient who reports stomach ulcers should avoid all the following foods except one. Which one is the exception?

a.
Proteins
b.
Caffeine
c.
Calcium
d.
Wheat

ANS:  D

Patients with ulcers of certain gastrointestinal tract disorders should avoid dietary constituents that increase hydrochloric acid and pepsin secretion. Foods to avoid include proteins, calcium, caffeine, coffee, and alcohol. Conversely, wheat (a whole grain), brown rice, and pastas are usually well tolerated because they do not typically stimulate gastric secretions. Note that although wheat is problematic in patients with gluten sensitivity, it is not contraindicated in patients with ulcers.

REF:   p. 57 | Dental Considerations

   27.   An adult stomach functions as a reservoir to hold an average meal for 6 to 8 hours. The rate of passage through the stomach (fastest to slowest) is liquids, proteins, carbohydrates, and fats.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  D

An adult stomach functions as a reservoir to hold an average meal for 3 to 4 hours. The stomach empties at different rates depending on its size and the composition of the chyme. The rate of passage, fastest to slowest, is liquids, carbohydrates, proteins, and fats. Note that fats remain in the stomach longer, increasing satiety for a longer time than proteins or carbohydrates.

REF:   p. 57

   28.   Most absorption occurs in the stomach because the gastric juices secreted by the stomach effectively hydrolyze and prepare nutrients for absorption.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  E

Very little absorption occurs in the stomach because few foods are completely hydrolyzed to nutrients the body can use at this stage. Nutrients that can be absorbed from the stomach include some water, alcohol, and a few water-soluble substances such as amino acids and glucose. Most of the energy-providing nutrients are completely hydrolyzed and absorbed within the small intestine.

REF:   p. 57

   29.   Which of the following is most likely to be absorbed within the stomach?

a.
Carbohydrates
b.
Fats
c.
Amino acids
d.
Fat-soluble vitamins

ANS:  C

Most of the energy-providing nutrients are completely hydrolyzed and absorbed within the small intestine. The only nutrients completely absorbed within the stomach are water, alcohol, and a few water-soluble substances such as amino acids and glucose. Note that little absorption occurs in the stomach because few foods are completely hydrolyzed to nutrients that the body can use at this point.

REF:   p. 58

   30.   Each of the following accurately describes aspects of the villi except one. Which one is the exception?

a.
Fingerlike projections called villi rise from the intestinal lumen.
b.
Villi decrease the surface area of the alimentary tract by contraction and compression.
c.
Each villus is covered with a layer of epithelial cells called microvilli.
d.
The brush border of cells is formed by microvilli.

ANS:  B

Villi increase the surface area of the alimentary tract to approximately 3000 square feet. Note that microvilli are minute cylindrical processes located on the surface of intestinal cells, greatly increasing their absorptive surface area.

REF:   p. 57

   31.   Intestinal digestion of fats and insoluble molecules is enhanced because emulsification by bile salts facilitates breakdown of such substances in to smaller particles.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  A

This question accurately describes emulsification, or breakdown of fats and soluble substances within the intestine. Importantly, emulsification allows greater exposure of fats to intestinal and pancreatic lipases. Peristalsis facilitates mixing and emulsification processes.

REF:   p. 57

   32.   Pancreatic enzymes enter the colon through the pancreatic duct. Produced and stored in the pancreas, these enzymes hydrolyze carbohydrates, proteins, and fats. Note that proteolytic enzymes, specifically designed to hydrolyze proteins, are also produced and stored in the pancreas.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  D

Pancreatic enzymes enter the duodenum through the pancreatic duct. The duodenum is the first section of the small intestine.

REF:   p. 57

   33.   Proteolytic enzymes are most likely to break down which food type?

a.
Carbohydrates
b.
Proteins
c.
Fats
d.
Lipids

ANS:  B

Proteolytic enzymes target and break down proteins. Notice that the names of most enzymes begin with the type of food it targets and end in -ase. For example, lipase breaks down fats, also known as lipids. Other enzymes, such as pancreatic enzymes, contain the full name of the organ from which it originates.

REF:   p. 57

   34.   Passage of a permeable substance from a more concentrated solution to an area of lower concentration is called osmosis. Transport requiring a carrier and cellular energy is active transport.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  D

Osmosis, active transport, and passive diffusion are three mechanisms that aid in transporting materials during absorption of nutrients. Passage of a permeable substance from a more to a less concentrated solution is called passive diffusion. Osmosis is the passage of water through a semipermeable membrane to equalize osmotic pressure exerted by ions in solutions. Active transport is accurately described in the question.

REF:   p. 59

   35.   Nutrients are absorbed from the small intestine through the mucosa into the portal circulation. Nutrients are transported through the portal vein to the liver where metabolism is initiated.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  A

The portal circulation enables passage of nutrients from the gastrointestinal tract and spleen through the portal vein to the liver. Most nutrients are absorbed from the small intestine through the mucosa into the portal circulation. The portal circulation delivers the nutrients to the liver where metabolism is initiated.

REF:   p. 59

   36.   Most nutrients are absorbed from the small to the large intestine, where the majority of digestion occurs. As the large intestine reabsorbs water and electrolytes, it forms the residue, also called feces.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  D

Almost no absorption occurs in the large intestine; most absorption occurs in the small intestine. The large intestine forms and stores the residue, or feces, until defecation. Residue in the intestinal tract is defined as the total amount of fecal solids.

REF:   p. 59

   37.   Each of the following is true of microflora within the colon except one. Which one is the exception?

a.
Approximately 50 different species of microorganisms compose the microflora.
b.
Microflora break down substances that human enzymes are unable to digest.
c.
Vitamin K and numerous B vitamins are synthesized by the microflora.
d.
Microflora inhibit pathogenic bacteria.

ANS:  A

More than 1 trillion harmless bacteria thrive in the colon. Approximately 400 different species or microorganisms compose the microflora within the colon. Proliferation of pathogenic, or harmful, bacteria is inhibited by the protective features of the microflora. Types of food and medications ingested influence the type, activity, and relative numbers of bacteria. When intestinal flora is unbalanced, overall health can be affected.

REF:   p. 60

   38.   Each of the following is true of protective elements within the microflora except one. Which one is the exception?

a.
Prebiotics are food ingredients that must be digested to stimulate growth and activity of microorganisms.
b.
Probiotics are living microorganisms that are considered food or dietary supplements in the United States.
c.
Symbiotics are a combination of prebiotics that support growth of probiotics.
d.
Probiotics are helpful in managing and treating constipation.

ANS:  A

Prebiotics are nondigestible food ingredients that have beneficial effects on the host by selectively stimulating the growth or activity, or both, of beneficial colonic microorganisms. Stated succinctly, prebiotics are food for probiotics. Probiotics together with prebiotics that support their growth are called symbiotics because they work together to promote probiotic benefits more efficiently. Although probiotics can help to regulate bowel habits and relieve constipation, they are frequently used to treat diarrhea and to prevent irritable bowel syndrome. Constipation means having a bowel movement fewer than three times per week with hard, dry, difficult-to-pass stools.

REF:   pp. 60-61

   39.   Each of the following is true of wheat sensitivity except one. Which one is the exception?

a.
Celiac disease is an autoimmune disorder caused by permanent gluten sensitivity.
b.
If not treated, celiac disease damages the microvilli in the small intestine.
c.
Gluten sensitivity is both an allergic reaction and an autoimmune disorder.
d.
Celiac disease is more common in people of European origin.

ANS:  C

Celiac disease and gluten sensitivity are two different conditions related to ingestion of gluten. Gluten is the structural protein component of the grains wheat, rye, barley, and triticale (a cross between wheat and rye). Whereas celiac disease is an autoimmune disorder, gluten sensitivity is neither allergic nor immunologic. Gluten-sensitive individuals are unable to tolerate gluten and can develop gastrointestinal symptoms, but the small intestine is not impaired (as is the case with celiac disease). A third category exists in which the patient develops an allergy to wheat.

REF:   pp. 62-63

   40.   Alveolar bone is primarily composed of bony spikes forming a meshwork of spaces within cancellous bone. This spikelike formation is called interdental bone.

a.
Both statements are true.
b.
Both statements are false.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  C

The spikelike formation of bone that forms a meshwork of spaces within cancellous bone is called trabecular bone. Cancellous bone is internal bone that appears spongy with little hollows that contain bone marrow.

REF:   p. 55

   41.   Lactose-intolerant individuals have a deficiency of both lactase and sucrase because breakdown of lactose involves conversion into two monosaccharides.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  D

Lactose intolerance is associated with a deficiency of lactase only. Although lactose is converted into two monosaccharides before exposure to gastric juices, the enzyme sucrose is not crucial. Note that sucrase is an enzyme necessary for proper metabolism of sucrose (sugar).

REF:   p. 52 | Nutritional Directions

   42.   Each of the following statements describes functions of the small intestine except one. Which one is the exception?

a.
Complete hydrolysis of most energy-providing nutrients
b.
Absorption of most vitamins and minerals
c.
Enzymatic breakdown of cellulose
d.
Secretion of digestive juices from its luminal wall

ANS:  C

Cellulose, a carbohydrate found in plants, cannot be completely digested because the human body lacks enzymes that can hydrolyze and break it down.

REF:   p. 51

   43.   Bile is produced and secreted by the liver and stored in the small intestine. Production of bile is stimulated by salivary amylase.

a.
Both statements are false.
b.
Both statements are true.
c.
The first statement is true; the second is false.
d.
The first statement is false; the second is true.

ANS:  B

Bile is produced and secreted by the liver and stored in the gallbladder. Production of bile is stimulated by cholecystokinin, a hormone released in response to fat in chyme. Note that acidic chyme entering the intestine stimulates hormones to release pancreatic juices.

REF:   p. 57

   44.   The basic hydrolysis reactions necessary for food digestion depend upon sugars because these complex carbohydrate-based substances enable completion of metabolic reactions at an efficient rate.

a.
Both the statement and the reason are correct and related.
b.
Both the statement and the reason are correct but are not related.
c.
The statement is correct, but the reason is not correct.
d.
The statement is not correct, but the reason is correct.
e.
Neither the statement nor the reason is correct.

ANS:  E

The basic hydrolysis reactions depend on enzymes, because these complex proteins are responsible for enabling completion of metabolic reactions at a fast rate without exhausting themselves.

REF:   p. 51

   45.   Each of the following is true of carbohydrate digestion except one. Which one is the exception?

a.
Digestion begins with salivary amylase.
b.
Hydrolysis begins within the mouth.
c.
Ptyalin is an enzyme involved in carbohydrate digestion.
d.
Xerostomia increases digestive function.

ANS:  D

Xerostomia, dry mouth from inadequate salivary section, leads to diminished digestive function. Much digestion, including that of carbohydrates, begins in the mouth with the action of salivary amylase. Note that this digestive enzyme, also called ptyalin, initiates starch digestion.

REF:   p. 57

   46.   Which substance is most essential for hydrolyzing large protein molecules?

a.
Gastric lipase
b.
Pepsin
c.
Mucus
d.
Intrinsic factor

ANS:  B

Although many enzymes are involved in hydrolysis and digestion, pepsin is essential for hydrolysis large protein molecules. Mucus forms an alkaline coating that protects the stomach lining from digestion by pepsin. Gastric lipase is involved in digestion of short-and medium-chain triglycerides. Intrinsic factor is secreted by the stomach and is essential for absorption of vitamin B12.

REF:   p. 57

   47.   Which enzyme is most essential for digestion of triglycerides found in butterfat?

a.
Gastric lipase
b.
Pepsin
c.
Mucus
d.
Intrinsic factor

ANS:  A

Gastric lipase is essential for digestion of short- and medium-chain triglycerides, such as those found in butter fat. Pepsin is essential for hydrolysis of large protein molecules. Mucus forms an alkaline coating that protects the stomach lining from digestion by pepsin. Intrinsic factor is secreted by the stomach and is essential for absorption of vitamin B12.

REF:   p. 57

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