Carb and Protein Digestion Module (Quiz) Flashcards
most dietary carbohydrates are
- large polysaccharides
- disaccharides
4 different forms of carbohydrates we consume
- starch
- sucrose
- lactose
- maltose
which two polysaccharides compose starch
- amylose
- amylopectin
both amylose and amylopectin are ______ polymers
- glucose
luminal digestion of starch begins in the mouth with the action of _______ and ends in the small intestine via action of ________
- alpha-amylase
- pancreatic alpha amylase
salivary and pancreatic amylase have optimum activities near _____ pH
- neutral
salivary amylase destroyed by ________
- acid in the stomach
where does most digestion of starch occur
- small intestine
role of pancreatic alpha-amylase
- hydrolyze alpha 1,4 bonds of amylose and amylopectin into alpha-limit dextrins
final digestive step of carbs occurs where
what happens?
- intestinal brush border
- intestinal brush border enzymes cleave oligosaccharides and disaccharide into glucose, fructose, and galactose which can be absorbed across the brush border
rate limiting step in sugar assimilation
- absorption of monosaccharides across brush border
under normal circumstances the majority of sugar assimilation is complete by the time it reaches ________
- proximal jejunum
do we have a cellulase capable of digestiing beta glucose bonds like are found in cellulose
- no
routes of absorption of carbohydrates
- SGLT-1
- GLUT-5
- GLUT-2
SGLT-1 transmembrane protein mediates transfer of __________ cross apical membrane.
occurs via ___________ transport
also allows transport of ______ and _____
- sodium and glucose
- sodium dependent secondary active transport
- galactose and glucose
unlike the SGLT-1 transmembrane protein which requires active transport, the GLUT-5 and GLUT-2 transmembrane proteins work via ___________
- passive diffusion
___________ facilitates the transport of fructose across the apical membrane into the cytosol
- GLUT-5
_________ allows for diffusion of glucose and galactose across basolateral membrane into the portal circulation
- GLUT-2
apical transport is _________ driven
- energy driven
the intestine is capable of transporting not just single amino acids but also _________
- short oligomers
the final stage of protein digestion takes place where?
- cytosol of the enterocyte
luminal digestion
proteolytic digestive enzymes are released in ______ forms first
- inactive zymogens
how does pepsinogen become activated into pepsin
- secreted into low pH environment in response to a meal
- undergoes autocatalytic cleavage
pepsins cleave dietary proteins at ______ amino acids
- neutral
pepsins inactivated at pHs ______
above 4.5
majority of products that come from proteolytic action of pepsin
- large non-absorbable peptides
- few free amino acids
the majority of proteolysis occurs where
- small intestinal lumen
classification of pancreatic proteases
- endopeptidases
- exopeptidases
endopeptidases cleave proteins and peptides at _______ bonds whereas exopeptidases cleave at _________
- internal amide bond (INTERNAL IS IMPORTANT)
- terminal amio acid (TERMINAL IS IMPORTANT)
endopeptidases include:
- trypsin
- chymotrypsin
- elastase
exopeptidases include:
- carboxypeptidase A and B
inactive zymogens converted into active forms via action of ___________
- trypsin
trypsin is produced as a result of cleavage by trypsinogen via enzyme _________
- enterokinase
enterokinase expressed on apical membrane of ______ epithelial cells
- duodenal
which proteins can be absorbed by carriers
- di and tri peptides
- free amino acids
small peptides are absorbed by a carrier with a _______ specificity
- broad
absorption of peptides is __________ of the Na+ gradient is stimulated by an inwardly directed ______ gradient maintained via an apical __________ exchanger
absorption of free amino acids is _______ on the Na+ gradient
- independent
- H+
- sodium-hydrogen
- dependent
peptides that enter enterocytes are further hydrolyzed by _______ to free amino acids
- cytoplasmic peptidases
how do free amino acids get into portal circulation
- carrier-mediated
- diffuse across basolateral membrane
lactose breaks into
- glucose
- galactose
