Dukes' Ch. 44: Digestion and Absorption of Nutrients

Question 1

With regard to digestion and absorption of dietary proteins:
A. Trypsinogen first becomes converted to trypsin by what?
B. Which cells produce this substance?
C. What stimulates these cells to produce the trypsin activating factor?

Answer 1

(A) Enteropeptidase
(B) villous enterocytes
(C) cholecystokinin

Question 2

With regard to the gall bladder:
A. Contraction of the gall bladder is stimulated by which hormone?
B. Made by which cells?
C. Located where?
D. Made in response to what stimulus?

Answer 2

(A) Cholecystokinin
(B) enteroendocrine cells
(C) duodenum
(D) fats and peptides entering the duodenum

Question 3

A micelle consists of fatty acids, monoglycerides, and cholesterol surrounded by what?

Answer 3

Bile salts

Question 4

Two proteolytic enzymes are produced by (A) _____ cells of the fundic gastric glands.
One is secreted as an inactive enzyme called (B) _____.
It is activated to its proteolytic form by (C) _____.
The other proteolytic enzyme is especially important to the neonatal mammal trying to digest its milk meals and is called (D) _____.

Answer 4

(A) Chief
(B) pepsinogen
(C) acid of stomach
(D) rennin

Question 5

Facilitated diffusion of tryptophan across the apical membrane of a villous cell in the jejunum requires which of the following? (List all correct answers)
A. Amino acid carrier protein
B. Sodium
C. Calcium
D. GLUT-2 transporter
E. ATP (directly)
F. Tryptophan cannot be transported across the jejunum

Answer 5

A and B

Question 6

Name three brush border membrane‐bound enzymes involved in the final stages of carbohydrate digestion in the villi of the jejunum.

Answer 6

Lactase, sucrase, maltase, trehalase, dextrinase, enterocyte amylase

Question 7

Number, in the order in which they occur (1, first to 9, last), the steps in fat digestion in a dog.
(A) CCK stimulates gallbladder contraction and secretion of pancreatic enzymes including pro‐colipase
(B) Micelles are formed, allowing the lipophilic contents to cross the unstirred water layer and glycocalyx of the villous enterocyte
(C) Chylomicrons exocytose through basolateral membrane and enter the lacteals
(D) Stomach contractions emulsify ingested fat
(E) Fat entering duodenum stimulates CCK release by enteroendocrine
cells
(F) Pro‐colipase is activated to colipase by trypsin in the lumen ofthe intestine
(G) Colipase, lipase and bile salts act together on emulsified fat to begin triglyceride breakdown
(H) Triglycerides are reformed and packaged in cholesterol–apolipoprotein B48 structures known as chylomicrons
(I) Micelles contact brush border membrane and fatty acids, monoglycerides, cholesterol and fat‐soluble vitamins cross cell membrane lipid bilayer into cytosol

Answer 7

D, E, A, F, G, B, I, H, C

Question 8

Magnesium citrate ingestion relieves constipation since Mg is not readily absorbed across the intestinal epithelium.
This causes an increase in __________ of the chyme, causing water to remain in the intestinal lumen and exit with the feces.

Answer 8

osmolarity

Question 9

Chloride is actively secreted into the lumen of the jejunum by which cells?

Answer 9

crypt cells

Question 10

Secreted by the crypt cells, chloride enters the cell from the blood/extracellular fluid:
A. With its concentration gradient and with its electrical gradient
B. With its concentration gradient and against its electrical gradient
C. Against its concentration gradient and with its electrical gradient
D. Against its concentration gradient and against its electrical gradient

Answer 10

B. With its concentration gradient and against its electrical gradient

Question 11

Glucose molecules are unable to cross the apical membrane by simple diffusion because they are (A) __________.
Fortunately, glucose can be cotransported across the apical membrane because of several forces that aid its movement.
These include the force generated by high glucose concentrations above the apical membrane during the final phases of brush border digestion.
The rest of the force needed to permit facilitated diffusion of glucose into the cell is provided by (B) __________ moving (C) with or against (choose one) its concentration gradient and (D) with or against (choose one) its electrical gradient.

Answer 11

(A) Too large
(B) Na+
(C) with its concentration gradient
(D) with its electrical gradient

Question 12

Volatile fatty acids are the end product of anaerobic bacterial fermentation within the rumen and colon of herbivores and are absorbed across the epithelium to serve as major energy sources for these species.
Many of the drugs you will utilize are also weak acids or weak bases.
These compounds are absorbed by a process known as (A) __________.
The weak acid or weak base only crosses the lipid bilayer membrane of absorptive cells when it is in the (B) __________ state.
For a weak base with a pKa of 10.8, absorption across the epithelium would be expected to occur most readily in the (C) stomach or jejunum (choose one).

Answer 12

(A) Nonionic diffusion
(B) nondissociated (uncharged) state
(C) jejunum

Question 13

A 5‐kg cat is brought into your clinic first thing in the morning and has diarrhea.
You are busy and put it into a clean stainless steel cage with a collection pan underneath; 4 hours later you return to look at the cat and notice there is loose fecal matter in the collection pan.
You skillfully measure the volume and discover there is about 40 mL of fluid fecal matter in the pan.
You feel confident that the problem in this cat is located in which section of the gastrointestinal tract?

Answer 13

Small intestine.

This volume of fluid (240 mL/day) could not come from the colon, even if it was unable to perform any absorption duties.