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CASE FILES: BIOCHEMISTRY
A nsw ers
[19.1]
D. a-Amylase hydrolyzes a(1^4) glycosidic bonds present in starch
(amylose and amylopectin) in a random fashion leaving primarily the
disaccharide maltose, the trisaccharide maltotriose, and an oligosac-
charide known as the a-limit dextrin, which is composed of 6 to 8
glucose residues with one or more a(1^6) glycosidic bonds.
Galactose and fructose are not present in starch.
[19.2]
B. Amylopectin is plant starch that has some a(1^6) branch points,
but not as many as normal glycogen. Glycogen, which has an
amylopectin-like structure, has fewer branch points than normal
glycogen and would be less soluble within the cell. A deficiency in
the branching enzyme will introduce fewer a(1^6) branch points.
[19.3]
E. Neither hormone sensitive lipase nor lipoprotein lipase is a diges-
tive enzyme. The patient’s symptoms are consistent with an inability
to absorb triglycerides, which would eliminate cholesteryl esterase
from consideration. Since the patient did not have any problems
while being breast-fed, then the most likely enzyme to be deficient is
pancreatic lipase, since gastric lipase is most active on short chain
triglycerides, such as those that are found in breast milk.
[19.4]
C. Lactase breaks down lactose into glucose and galactose.
[19.5]
B. Sucrase breaks down sucrose into glucose and fructose.
[19.6]
D. Maltase and isomaltase convert maltose and isomaltose into glucose.
B IO C H E M IS T R Y PE A R L S
The pancreas is a large exocrine organ that has a role in the diges-
tion of food as well as an endocrine organ which secretes insulin,
somatostatin, and glucagon.
Acute pancreatitis occurs from autodigestion of the acinar cells by
inappropriate activation of the pancreatic enzymes (especially
trypsinogen) within the cell, leading to cellular injury mediated
by proinflammatory cytokines.
The three major breakdown products of amylase are maltose, mal-
totriose, and a-dextrins. Enzymes in the brush border of the
intestines continue to digest the carbohydrates.
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