143b - Absorption of Carbohydrates and Proteins Flashcards
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
a. CCK
The gastric zymogen, pepsinogen, is converted to the active enzyme pepsin by:
a. Gastric HCl
b. Gastrin
c. Enterokinase
d. Acetylcholine
e. Intrinsic factor
a. Gastric HCl
- Enterokinase converts trypsinogen -> tripsin; important for activation of pancreatic enzymes
- Intrinsic factor is important for absorption of vitamin B12
What are the most common disaccharides in our diet?
What monosaccharides are they compsed of?
Sucrose = glucose + fructose
Lactose = glucose + galactose
What is the role of the pancreas in protein absorption?
- 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
Absorption of which monomers are driven by the Na+/K+ ATPase? (2)
- Glucose
- Amino acids
(Not fatty acids)
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
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
Which enzyme activates pancreatic proenzymes?
Trypsin
(Enterokinase activates trypsinogen -> trypsin)
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?
- Endopeptidases
- Break oligosaccharides into monomers (glucose, galactose, fructose)
- Aminopeptidases
- Break small polypeptides into free amino acids, dipeptides, and tripeptides
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
a. absorption of 2-monoglycerides
Are carbohydrates digested in the stomach?
No
- Amylase is not active at low pH; it is denatured by gastric acid
- Pancreatic alpha-amylase picks up in the duodenum
Which carbohydrate bonds can be broken by alpha-amylase?
Internal 1,4 bonds
Both salivary and pancreatic amylase can only break up 1,4 polysaccharaide bonds.
Where are the other enzymes necessesary for carbohydrate digestion located?
Brush border of the small intestine
- Lactase
- Sucrase
- Maltase
- Lucoamylase
- Alpha-dextrinase (isomaltase)