GI5 Flashcards
what are three things that amplifies surface area?
- folds
- villi and crypts
- microvilli
the epithelium lining in the small intestine is ____
leaky
what part of the crypt contains digestive enzymes?
glycocalyx
what cells of the crypt secrete antimicrobial peptides?
paneth cells
are there stem cells in the crypt?
yes
what layer presents a barrier to diffusion in the gut?
unstirred layer
what two things make up the unstirred layer?
- glycocalyx layer
- mucous layer
nutrients must pas though what layer in order to be absorbed?
unstirred layer
what is the overarching goal of digestion?
-reduce particle size to enable absorption
what is hydroysis?
splitting of a chemical bond by the insertion of water
what type of bonds are in carbs?
glycosidic bonds
what type of bonds are in proteins?
peptide bonds
what type of bonds are in fats?
ester bond
what type of bonds are in nucleic acids?
phosphodiester bonds
what do digestive enzymes do?
catalyze hydrolysis
what phase are proteins and starch hydrolyzed?
luminal phase, active withing the gut lumen
what phase are polysaccharides and peptides hydrolyzed?
membranous phase, active at the gut epithelial surface
where is the enzyme origin for luminal phase?
- salivary glands
- gastric glands
- pancreas
where is the enzyme origin for membranous phase?
-apical membrane of enterocytes
what is starch comprised of?
amylose and amylopectin
is amylose straight or branched?
straight
is amylopectin straight or branched?
branched
which peptidase can only cleave in the middle of a protein, and cannot release free amino acids?
endopeptidases
which peptidase can cleave at the ends and release individual AAs?
exopeptidase
what is a key pancreatic zymogen activator?
trypsin
at what pH does pepsin have maximal activity?
pH 1-3
T/F: the stomach is essential for digestion and survival.
false
lactose breaks down into:
glucose and galactose
sucrose breaks down into
glucose and fructose
starch breaks down into
glucose
GLUT5 carriers what?
glucose and fructose
SGLT1 carries what?
glucose and galactose
enterocytes absorb short peptides and free AAs but release only ___ ___ ___ into the blood.
-free amino acids
many uptake uptake mechanisms are coupled to ____ movement.
Na+
what is the first step of the absorptive process?
luminal uptake
