Digestion & Absorption - CHOs & Proteins Flashcards
glucose, galactose, and galactose are all
monosaccharides
only what kind of carb is absorbed by intestinal epithelial cells
monosaccharides
digestion of starch begins with
α amylase
what happens to α amylase when it reaches stomach
inactivated b/c of the low pH
amylase in pancreas vs. saliva
more potent in pancreas, completes the digestion of carbs
amylase from pancreas that is working in SI, what does it do to starch
digests to disaccharide
if starch is digested to disaccharide, list the diasacchrides that make it up
maltose
sucrose
lactose
what are the intestinal brush border enzymes
α dextrinase
maltase
sucrase
what enzymes do the final digestion of disaccharides to monosaccharides
brush border enzymes
glucose, galactose, and fructose can all be absorbed by
intestinal epithelial cells
what monosaccharides make up trehalose
glucose
what monosaccharides make up lactose
glucose & galactose
what monosaccharides make up sucrose
glucose & fructose
glucose and galactose are absorbed across what part of cell
apical membrane
what transport mechanism is used to absorb glucose and galactose
secondary active transport
what transporter is used to move glucose and galactose
SGLT1 (Na+ Glucose cotransporter)
once the cell absorbs glucose and galactose, it extrudes it into blood via what mechanism of transport
facilitated diffusion GLUT2
what transporter is used to transport glucose and galactose into blood from epithelial intestinal cell
GLUT2
what happens if there is SGLT1 cotransporter defect
accumulation of glucose & galactose in lumen
body can’t absorb enough water
diarrhea
what method of transport is used to move absorb fructose
facilitated diffusion
what is the name of the fructose transpoter in apical membrane
GLUT5
what is the name of the fructose transporter in basolateral membrane
GLUT2
fructose can never be absorbed against its
electrochemical gradient
what does ORT stand for
oral rehydration therapy
draw out the absorption of CHOs
pg 9
what is the most common CHO malabsorption syndrom
lactose intolerance
lactose intolerance is due to decreased expression of
lactase
explain lactose intolerance and it’s symptoms
can’t absorb lactate. don’t have lactase or much less lactase. since lactose stays in GI, build up of water in it, can get cramping, gas, diarrhea
what are two diagnostic tests for lactose intolerance
hydrogen breath test
lactose tolerance blood test
explain the hydrogen breath test
testing for lactose intolerance
pt fasts
then given pure lactose
take hydrogen levels on breath
explain lactose tolerance blood test
blood samples taken before digesting lactose, then after. looking at amount of glucose in blood
why is there higher hydrogen excretion for pts who are lactose intolerant after they ingest lactose
colonic bacteria metabolize the lactose and produce H2
where are CHOs absorbed
SI
where are proteins absorbed
SI
what are absorbable forms of proteins
AA
dipeptides
tripeptides
digestion of proteins begins where
stomach
what beings the digestion of proteins in stomach
pepsin
digestion of proteins is completed where
SI
what enzymes in SI digest proteins
pancreatic & brush border proteases
what are two classes of proteases
endopeptidases & exopeptidases
what do Endopeptidases do? (how do they function)
hydrolyze interior peptide bonds of proteins
what are the Endopeptidases of the GI tract
pepsin, trypsin, chymotrypsin, and elastase
what do Exopeptidases do? (how do they function?)
hydrolyze one amino acid at a time from the C-terminal ends of proteins and peptides.
what are the exopeptidases of the GI tract
carboxypeptidases A and B.
what cell secretes pepsinogen
chief cells
above pH 5 what happens to pepsin
denatured & inactivated
is pepsin needed for normal protein digestion?
no
what is the only thing needed for normal protein digestion
pancreatic & brush border proteases
what enzyme activates trypsinogen
enterokinase
once a little trypsin has been catalyzed, what happens
it catalyzes reaction of all other inactive precursers to their active form, and then autocatalyzes more trypsinogen to make more trypsin
what 5 enzymes are activated b/c of trypsin
trypsin, chymotrypsin, elastase, carboxypeptidase A, and carboxypeptidase B
what happens to oligopeptides
they can’t be absorbed so theya re further hydrolyzed by brush border proteases
how are L-amino acids abosrbed, by what mechanism
Na+ aa cotransporter
what part of cell are Na+ aa cotransporter located
apical membrane
how many different Na+ aa cotransporters are there?
4 = neutral, acidic, basic, imino
once L-amino acids are absorbed by cell, how are they transported across basolateral membrane into blood
facilitated diffusion
L-amino acid absorption is similar to what
monosaccharide in duodenum and upper jejunum
how are dipeptides and tripeptides absorbed, by what transporter
H+ dependent cotransporter
where is H+ dependent cotransporter located on cell
apical membrane
what happens to dipeptides and tripeptides once they are absorbed
they are broken down to AA by peptidases
after dipeptides and tripeptides are absorbed how do they exit into blood
the ones that were broken down to AA leave by facilitated diffusion
the leftover dipeptides and tripeptides are absorbed unchanged
in disorders of exocrine pancreas, there is a deficiency of what
all pancreatic enzymes
name two example disorders of exocrine pancreas
cystic fibrosis
chronic pancreatitis
what diseases are caused by defect or absence of Na+ AA cotransporter
hartnup disease
cystinuria
what causes hartnup disease
impaired neutral amino acid transport in the apical brush border membrane of the small intestine and the proximal tubule of the kidney
there is decreased reabsorption of what in hartnup disease
neutral AAs
due to the decreased absorption of neutral AA by kidney and SI in hartnup, what happens to urine
aminoaciduria
what is aminoaciduria
AAs in urine
lack of trytophan in hartnup may cause
signs of pellagra
what causes pellagra
vitamin B3 deficiency
what are symtpoms of hartnup if untreated
Diarrhea, light-sensitive dermatitis, dementia and death within 4-5 yrs if untreated.
how can their be neurological symptoms in hartnup
Presence of unabsorbed amino acids in colon results in metabolism by bacteria to toxic amines
what is treatment for hartnup disease
High-protein diet, avoid exposure to sun, nicotinamide for dermatitis and neurologic symptoms, and psychiatric support for patients with CNS involvement
what causes cystinuria
transporter for dibasic AA is absent in SI and kidney
what are the dibasic AA
cystine, lysine, arginine, and ornithine
what symptoms will occur b/c of lack of cystine absorption in cystinuria
Cystine precipitates, or crystallizes out of urine and forms stones (calculi) in the kidney, ureter, bladder, or anywhere in the urinary tract.
what are the intestinal defects in cystinuria
failure to absorb basic amino acids which are excreted in feces
Nausea/Vomiting
Dull ache or “colicky” pain
Flank pain (pain in the side, due to kidney pain) Hematuria (blood in urine)
Obstructive uropathy (urinary tract disease due to obstruction)
Urinary tract infections
these are all symptosm due to?
cystinuria, but b/c the pt got a stone
what is treatment of cystinuria
Hydration to increase urine output, meds to reduce kidney stones and relieve pain, eating less salt, and shock wave therapy for large stones.
what is brush border
intestinal epithelial cells
paracellular pathway plays bigger role in absorption of electrolytes and water where
at beginning of GI tract than colon
if there is a problem with SGLT1 what happens
osmotic diarrhea
if you have problem with SGLT1 how do you maintain good carbohydrate absorption
high fructose diet
under normal conditions is glucose and galactose present in colon
no
are oligopeptides absorbable?
NOOOO
where is enterokinase released from
enteroepithelial cell
draw out protein absorption in cell
pg 27
if you have absence of trypsinogen or enterokinase, what happens to activation of trypsinogen
will go down, can’t convert to trypsin and can’t autophosphorylate
most protein you ingest is what form
dipeptide tripeptide form
CCK is in response to what coming into duodenum
chyme
