143b - Absorption of Carbohydrates and Proteins

Question 1

Which of the following hormones is released by the presence of fat and protein in the small intestine and helps to decrease gastric emptying?

a. CCK
b. GIP
c. Gastrin
d. Motilin
e. Secretin

Answer 1

a. CCK

Question 2

The gastric zymogen, pepsinogen, is converted to the active enzyme pepsin by:

a. Gastric HCl
b. Gastrin
c. Enterokinase
d. Acetylcholine
e. Intrinsic factor

Answer 2

a. Gastric HCl

• Enterokinase converts trypsinogen -> tripsin; important for activation of pancreatic enzymes
• Intrinsic factor is important for absorption of vitamin B12

Question 3

What are the most common disaccharides in our diet?

What monosaccharides are they compsed of?

Answer 3

Sucrose = glucose + fructose

Lactose = glucose + galactose

Question 4

What is the role of the pancreas in protein absorption?

Answer 4

• Acinar cells secrete enzymes (in response to CCK)
  
  • Trypsinogen
  • Chymotrypsinogen
  • Proelastase
  • Procarboxypeptidase A and B
• Ductal cells secrete bicarbonate (in response to secretin)
  
  • Prevents degradation of enzymes
  • If pH is too low (too much stomach acid), the pancreatic enzymes won’t work

Question 5

Absorption of which monomers are driven by the Na+/K+ ATPase? (2)

Answer 5

• Glucose
• Amino acids

(Not fatty acids)

Question 6

Which one of the following is NOT stimulated by CCK?

a. secretion of bile by the liver
b. secretion of pancreatic HCO3-
c. secretion of pancreatic enzymes
d. relaxation of the sphincter of Oddi
e. contraction of gall bladder smooth muscle

Answer 6

a. secretion of bile by the liver

• CCK stimulats release of bile from the gallbladder
• Bile synthesis in the liver is not under control of CCK

Question 7

Which enzyme activates pancreatic proenzymes?

Answer 7

Trypsin

(Enterokinase activates trypsinogen -> trypsin)

Question 8

What kinds of enzymes are located on the brush border of the small intestine? (2)

They are necessary for the digestion and absorption of which nutrients?

Answer 8

• Endopeptidases
  
  • Break oligosaccharides into monomers (glucose, galactose, fructose)
• Aminopeptidases
  
  • Break small polypeptides into free amino acids, dipeptides, and tripeptides

Question 9

Which function would NOT be directly affected by inhibition of the Na+/K+ ATPase?

a. absorption of 2-monoglycerides
b. absorption of galactose
c. secretion of bile salts by the liver
d. absorption of amino acids
e. salivary secretion

Answer 9

a. absorption of 2-monoglycerides

Question 10

Are carbohydrates digested in the stomach?

Answer 10

No

• Amylase is not active at low pH; it is denatured by gastric acid
• Pancreatic alpha-amylase picks up in the duodenum

Question 11

Which carbohydrate bonds can be broken by alpha-amylase?

Answer 11

Internal 1,4 bonds

Question 12

Both salivary and pancreatic amylase can only break up 1,4 polysaccharaide bonds.

Where are the other enzymes necessesary for carbohydrate digestion located?

Answer 12

Brush border of the small intestine

• Lactase
• Sucrase
• Maltase
• Lucoamylase
• Alpha-dextrinase (isomaltase)