Deck 25: Digestion and Absorption of Basic Nutritional Constituents

Question 1

Human bile contains all of the following EXCEPT

A) glycocholic acid.
B) mucin.
C) phosphoglycerides.
D) triacylglycerol.
E) taurocholic acid.

Answer 1

phosphoglycerides.

Question 2

Sucrose is composed of

A) two residues of D-glucose.
B) one residue each of D-glucose and D-fructose.
C) one residue each of D-glucose and D-galactose.
D) one residue each of D-galactose and D-fructose.
E) two residues of D-fructose.

Answer 2

one residue each of D-glucose and D-fructose.

Question 3

The digestion and absorption of starch involves hydrolysis to glucose

A) followed by an antiport mechanism of absorption.
B) followed by phosphorylation and absorption of the glucose phosphate.
C) followed by absorption after conjugation with glutathione.
D) followed by absorption via a symport mechanism.
E) after endocytosis of starch by intestinal epithelial cells.

Answer 3

followed by absorption via a symport mechanism.

Question 4

An enzyme present in saliva which hydrolyzes starch to produce free maltose is

A) sucrase.
B) alpha-amylase.
C) phosphorylase.
D) debranching enzyme.
E) limit dextrin.

Question 5

Which enzyme is responsible for the conversion of pepsinogen to pepsin?

A) enteropeptidase
B) gastrin
C) pepsin
D) trypsin
E) Both B and C are correct.

Question 6

Which molecule is a zymogen activated by hydrolysis in the intestine?

A) trypsinogen
B) chymotrypsin
C) carboxypeptidase
D) enterokinase
E) pepsinogen

Question 7

Which of the following compounds would you suggest be eliminated from the diet of a patient suffering from galactosemia?

A) leucine
B) starch
C) lactose
D) glucose
E) none of the above

Question 8

bile salts are stored in the

A) gall bladder.
B) liver.
C) small intestine.
D) all of the above.

Question 9

The action of pancreatic amylase followed by maltase on starch would yield

A) fructose, isomaltose and glucose.
B) maltose, alpha-dextrins and lactose.
C) amylose and alpha-dextrins.
D) maltotriose, glucose and alpha-dextrins.
E) maltose, maltotriose and amylose.

Question 10

What type of cells have secretagogue receptors?

A) Autocrine
B) Endocrine
C) Exocrine
D) Juxtacrine
E) Paracrine

Question 11

All of the following are true of mixed micelles formed in the intestine EXCEPT which one?

A) They provide a vehicle for the absorption of fat soluble vitamins.
B) They are absorbed directly into the lymphatic system via the lacteals.
C) Cholesterol is often a component of micelles.
D) Micelles contain mainly free fatty acids and monoacylglycerols.
E) The non-polar ends of lipids are oriented toward the center of the micelles.

Question 12

The formation of chylomicrons takes place in the

A) adipose tissue where stored triacylglycerols are mobilized.
B) small intestine where dietary triacylglycerols are digested and absorbed.
C) liver where cholesterol and apolipoproteins are synthesized.
D) blood where circulating lipoproteins are degraded by lipases.

Question 13

Which enzyme of intestinal origin activates trypsinogen?

A) pepsin
B) carboxypeptidase
C) chymotrypsin
D) enterokinase
E) cholecystokinin

Question 14

In the transport of glucose from the intestinal lumen through the epithelial cells, which of the following is NOT true?

A) A metabolic poison (cyanide) or absence of oxygen would have no effect.
B) It requires sodium, potassium ATPase.
C) It is unidirectional.
D) It is stereospecific.
E) Cotransport with sodium occurs.

Question 15

What are the total products of triglyceride digestion in the lumen of the small intestines?

A) Free glycerol and free fatty acids.
B) 2-Monoglycerides and free fatty acids.
C) 1-Monoglycerides and free fatty acids
D) 2-Monoglycerides, free glycerol and free fatty acids.
E) Diglycerides and free fatty acids.

Question 16

Pancreatic lipase is an enzyme which

A) hydrolyzes triglycerides to glycerol plus fatty acid.
B) specifically attacks the 2-position of triglycerides.
C) specifically attacks the 1- and 3-ester linkages of triglycerides.
D) specifically hydrolyzes 2-monoglycerides to glycerol and fatty acid.
E) specifically hydrolyzes phospholipids.

Question 17

All of the following statements are correct EXCEPT which one?

A) triglyceride digestion requires a lipase produced by the pancreas.
B) triglycerides can be emulsified in the gut using bile salts.
C) Phospholipids can aid emulsification of triglycerides in the gut.
D) lipases use water as a cosubstrate.
E) Long chain acyl-CoA's are products when lipases degrade triglycerides.

Question 18

Which enzyme is an endopeptidase secreted as a zymogen by the pancreas?

A) trypsin
B) pepsin
C) amylase
D) enterokinase
E) carboxypeptidase

Question 19

Which of the following is the main carrier for the transport of digested fat?

A) chylomicron
B) VLDL
C) LDL
D) HDL
E) albumin

Question 20

Chymotrypsin is

A) an enterokinase.
B) an endopeptidase.
C) a carboxypeptidase.
D) the precursor of trypsin.
E) an aminopeptidase.

Question 21

All of the following occur at or in the brush border (microvilli) of intestinal mucosal cells EXCEPT which one?

A) Na⁺-driven cotransport of amino acids.
B) Na⁺-driven cotransport of fatty acids.
C) Na⁺-driven cotransport of glucose.
D) conversion of dipeptides to amino acids.
E) uptake of monoglycerides.

Question 22

Which transport mechanism is unique to parietal cells for the transport of HCl?

A) Cl^-/HCO3^- exchanger
B) Cl^-/Na⁺ antiporter
C) Electrogenic Cl- flux
D) K⁺/H⁺ -exchanging ATPase
E) Na⁺/H⁺ transporter

Question 23

Which type of reaction BEST characterizes the process of digestion?

A) hydrolysis
B) dehydration
C) dehydrogenation
D) phosphorolysis
E) hydrogenation

Question 24

Enzymes involved in the digestion of dietary protein in the small intestine include all of the following EXCEPT

A) trypsin
B) elastase
C) chymotrypsin
D) carboxypeptidase A
E) pepsin

Question 25

Which of the following statements about bile acids is CORRECT?

A) bile acids are required for the absorption of vitamins A and K
B) Taurodeoxycholic acid is a primary conjugated bile acid.
C) Glycochenodeoxycholic acid is a secondary conjugated bile acid.
D) The presence of high concentrations of bile acids stimulates the synthesis of additional bile acids.
E) The rate-limiting step in their synthesis is decarboxylation.

Question 26

Pancreatic enzymes cannot catalyze the complete digestion of dietary proteins to amino acids in the intestine because

A) pancreatic proteases are zymogens.
B) the pH in the small intestine is unfavorable for activity of pancreatic proteases.
C) pancreatic proteases are endopeptidases.
D) bacteria destroy pancreatic proteases in the small intestine.
E) pepsin from the stomach is required to activate pancreatic proteases.

Question 27

The processes involved in the secretion of enzymes and electrolytes in the digestion system are regulated and coordinated by which of the following substances?

A) acetyl choline
B) histamine
C) serotonin
D) gastrin
E) all of the above

Question 28

Which of the following is produced by the liver?

A) trypsinogen
B) chymotrypsinogen
C) carboxypeptidase
D) enterokinase
E) glycocholic acid

Question 29

What do cardiac glycosides inhibit?

A) Cl-/HCO3- transporter
B) Electrogenic Na+ flux
C) Na⁺/H⁺ transporter
D) Na⁺/K⁺/2Cl- cotransporter
E) Na⁺/K⁺-exchanging ATPase

Question 30

Dietary triacylglycerols are mainly hydrolyzed in the intestinal tract by

A) hepatic lipase to glycerol and fatty acids.
B) hormone-sensitive lipase to glycerol and fatty acids.
C) hormone-sensitive lipase to monoacylglycerol and fatty acids.
D) pancreatic lipase to diacylglycerol and fatty acids.
E) pancreatic lipase to monoacylglycerol and fatty acids.

Question 31

Absorption of all the major nutrients (fat, protein, polysaccharide) from the gut has which of the following characteristics?

A) Active transport is required.
B) ATP hydrolysis, when employed, results in heat production, not useful work.
C) The products absorbed are typically derived by hydrolysis of larger molecules.
D) Absorption results exclusively in entry into the portal circulation.
E) In each case where ATP is employed, the absorbed substance is phosphorylated.

Question 32

Most nutrients are absorbed in the:

A) Colon
B) Large intestine
C) Small intestine
D) Stomach

Question 33

All of the following are part of the process of protein digestion EXCEPT

A) denaturation of many proteins at the pH of gastric juice.
B) the action of enteropeptidase (enterokinase) on pro-aminopeptidase.
C) conversion of pepsinogen to pepsin by the action of pepsinogen.
D) catalysis of protein hydrolysis by both endo- and exopeptidases.
E) the action of specific dipeptidases.

Question 34

Which statement about protein digestion in the stomach and intestines is FALSE?

A) Trypsin can activate all zymogens of pancreatic proteases.
B) pepsin is irreversibly inactivated when the pH is above 5.
C) Chymotrypsin and trypsin show similar specificity in catalyzing the hydrolysis of peptide bonds.
D) The action of pepsin in the stomach produces primarily peptide fragments of proteins.
E) Intestinal peptidases are required to digest di- and tri-peptides.

Question 35

Alpha-1,6-glucosidase is an enzyme in humans which is

A) found in salivary and pancreatic secretions.
B) secreted by cells of the gastric mucosa.
C) located in the epithelium of the large intestine.
D) elaborated by cells in the duodenum.
E) a constituent of bile.

Question 36

The major site of digestion of dietary fats is the

A) stomach.
B) liver.
C) small intestine.
D) duodenum.
E) large bowel.

Question 37

Monoglycerides formed by digestion of unmodified animal fats usually contain

A) a saturated fatty acid residue.
B) an unsaturated fatty acid residue.
C) about equal amounts of saturated and unsaturated fatty acid residues.

Question 38

A typical property of a detergent is the formation of a micelle in solution. Under which of the following conditions is a detergent least likely to form micelles?

A) at high detergent concentrations
B) in the presence of other amphipathic molecules
C) in the presence of low amounts of lysolecithin
D) at low detergent concentrations
E) None of the above; detergents always form micelles.

Question 39

Cellulose is not digested by humans because it

A) is a relatively insoluble protein-carbohydrate complex inaccessible to digestive enzymes.
B) is a mucopolysaccharide, which is not a substrate for digestive enzymes.
C) is highly sulfated, making it inaccessible to the action of most glycosidases.
D) is a polymer of glucose molecules in beta 1-4 linkage for which we have no digestive enzymes.
E) resists enzyme action due to its highly branched structure.

Question 40

Which molecule is synthesized in the stomach as a precursor of a proteolytic enzyme?

A) pepsinogen
B) trypsinogen
C) chymotrypsin
D) enterokinase
E) progastrin

Question 41

All of the following statements about alpha-amylase are correct EXCEPT which one?

A) Small branched dextrins are poor substrates for the enzyme.
B) Amylopectin and glycogen are normal substrates.
C) The major product of its action on amylose is glucose.
D) The enzyme catalyzes the hydrolysis of alpha-1,4-glucosidic linkages.
E) For humans, the most important occurrence of the enzyme is in the secretion of the pancreas.

Question 42

Lactose intolerance is caused by deficient activity of

A) galactose 1-phosphate uridylyltransferase.
B) amylase.
C) lactose dehydrogenase.
D) lactase.
E) galactokinase.

Question 43

Zymogens of gastric and pancreatic proteases are activated by

A) aggregation of monomers.
B) glycosylation.
C) formation of covalent crosslinks.
D) proteolysis.
E) association with coenzymes.

Question 44

Which of the following statements is true concerning secretagogues?

A) They are secreted by exocrine glands into the digestive tract
B) They stimulate the secretion of calcium ions into the digestive tract
C) They may be comprised of neurotransmitters and hormones that act on exocrine cells
D) They are cleaved by digestive enzymes and absorbed into small intestine
E) They are released as zymogens from exocrine cells

Question 45

Which digestive enzyme is NOT synthesized in the pancreas and secreted into the lumen of the intestine as a zymogen?

A) aminopeptidase
B) trypsin
C) chymotrypsin
D) elastase
E) carboxypeptidase B

Question 46

The intestinal cell is probably unique in that it can

A) Synthesize lipoprotein.
B) Acylate monoglyceride to form triglyceride.
C) Synthesize phosphatidic acid.
D) Absorb free fatty acids.
E) Utilize glucose to form glycerol phosphate.

Question 47

All of the following would be able to function as emulsifying agents in water EXCEPT which one?

A) sphingomyelin
B) 2-acylglycerol
C) phosphatidylcholine
D) sodium stearate
E) cholesterol ester

Question 48

Bile salts are synthesized in the

A) gall bladder.
B) liver.
C) small intestine.
D) all of the above.

Question 49

Dietary triglycerides are absorbed primarily as

A) 1,3 diglycerides.
B) intact triglyceride.
C) 1,2 diglyceride.
D) 1 monoglyceride.
E) 2 monoglyceride.

Question 50

Concerning the bile acids, which of the following statements is/are CORRECT

A) glycocholic and taurocholic acids are the major conjugated bile acids.
B) some of the conjugated bile acids are returned to the liver from the intestine via the enterohepatic circulation.
C) the major lipid components of bile, besides the conjugated bile acids, are phosphatidyl choline and cholesterol.
D) all of the above.
E) none of the above.

Question 51

Which protein is synthesized in the intestine?

A) trypsinogen
B) chymotrypsinogen
C) procarboxypeptidase
D) enterokinase
E) pepsin

Question 52

The major function of chylomicrons is transport of

A) cholesterol from the liver to peripheral cells.
B) dietary triglycerides to peripheral tissues.
C) fatty acids from the adipose tissue to energy-requiring tissues such as skeletal muscle.
D) endogenous triglycerides from the liver.
E) cholesterol from peripheral tissues to the liver for disposal.

Question 53

The major site of carbohydrate digestion is the

A) mouth.
B) stomach.
C) small intestine.
D) large intestine.
E) pancreas.

Question 54

In a patient who has had a significant portion of the stomach removed in surgery, the action of which of the following enzymes would be significantly reduced?

A) trypsin
B) enteropeptidase
C) elastase
D) pepsin
E) carboxypeptidase A

Question 55

Lactase catalyzes which of the following?

A) galactose --> glucose + glucose 6-phosphate
B) sucrose --> glucose + fructose
C) lactate --> glucose + galactose
D) lactose --> glucose + galactose
E) lactate --> pyruvate

Question 56

What is the principal physiological function of bile salts?

A) To permit cholesterol catabolism.
B) To catalyze lipid digestion.
C) To permit gastrointestinal absorption of dietary lipid.
D) To control enterohepatic circulation.
E) To regulate blood cholesterol levels.

Question 57

Glucose absorption:

A) occurs without the need for a transport protein in muscle cells.
B) needs an active Na+ pump in liver cells.
C) requires insulin in the brain.
D) is stimulated by glucagon in the liver.
E) occurs against a concentration gradient in the intestinal mucosa.

Question 58

Digestive enzymes operating within the gastrointestinal tract may be contributed by each of the following EXCEPT

A) synthesis in the liver.
B) synthesis in the gastric mucosa.
C) synthesis in the pancreas.
D) synthesis in the intestinal mucosa.
E) bacterial flora.

Question 59

Which of the following is involved in the conversion of a zymogen into an active enzyme in the intestine?

A) carboxypeptidase
B) cholecystokinin
C) pepsin
D) enterokinase
E) all of the above

Question 60

Chylomicrons are

A) produced in the gut, and contain triglycerides, cholesterol, cholesteryl esters, protein, phospholipids.
B) produced in the liver and contain triglycerides, cholesterol, cholesteryl esters, protein, phospholipids.
C) produced in the intestine and the liver and contain largely cholesterol and phospholipids.
D) produced in the intestine and contain bile salts in addition to triglycerides, cholesterol and phospholipids.
E) the smallest of the serum lipoprotein particles.

Question 61

The complete digestion by humans of starch or glycogen to glucose requires

A) only amylase.
B) only phosphorylase.
C) amylase, an oligo-alpha-1,6-glycosidase, and a maltase.
D) amylase and sucrase.
E) a poly-alpha-1,4-glucosidase.

Question 62

Primary bile acids are

A) any bile acids found in the small intestine.
B) any bile acids reabsorbed from the small intestine.
C) synthesized in the small intestine by bacteria.
D) synthesized in the liver from cholesterol.
E) converted to secondary bile acids by conjugation with glycine or taurine.

Question 63

Medium-chain triacylglycerols

A) are absorbed intact in the small intestine and are transported in the thoracic duct to blood as chylomicrons.
B) are not utilized in man because of a lack of pancreatic lipase specific for medium-chain triacylglycerols.
C) are readily absorbed in the small intestine and are transported in the portal vein.
D) contain mostly fatty acids having a chain length of 14-16 carbons.
E) none of the above.

Question 64

Which is classified as an exopeptidase?

A) trypsin
B) chymotrypsinogen
C) carboxypeptidase
D) enterokinase
E) pepsin