130b carb and protein metabolism Flashcards
What is the only monosacchride OR amino acid that can be absorbed through facilitated diffusion without Na dependent transport?
fructose
monosacc = FGG
What basic element must proteins and carbs/starches be broken down to in order to absorb in intestine? How mechanism is used for absorption (except fructose)?
amino acids OR di/tri-peptides
simple monosaccarides (fructose, glucose, galactose)
Na-cotransport for monosacc and aa
H+ cotransport for di/tri peptides
what type of carb are refined sugars found in the diet?
what are the 3 types and what are they made of?
disaccharides
sucrose (table sugar)= glucose + fructose
Maltose = 2 glucose
Lactose=glucose + galactose
carb digestion in mouth - what does it? what bond does it break? what is left over?
a-amylase
breaks internal a-1,4 linkages (not external a-1,4 or a-1,6)
maltose (2 glucose)
maltotriose (3 glucose)
dextrins (5-9 glucose polymers with 1,6 links)
none of these are absorbable without further digestion; must break down into monosaccrides
Once oligosaccharides reach the small intestine, where are things that break them down located? by what?
brush border of enterocyctes
Lactase (lactose –> glucose + galactose)
Sucrase (sucrase –> glucose + fructose)
maltase – breaks 1,4 bonds of maltose –> 2 glucose
isomaltase – breaks 1,6 bonds of dextrins –> 1,4 glucose polymers + glucose
where are carbs absorbed in the small intestine?
duodenum and upper jejunum
what transports glucose and galactose into enterocytes? ATPase?
SGLT1 carrier - sodium dep glucose transporter
Not an ATPase, uses gradient for Na/K ATPase
high fructose corn syrup
50% sucrose
50% fructose
sweeter than sugar and much cheaper
fructose transportation into enterocytes? active? up or down gradient?
GLUT5 carrier
doesn’t require E
down a concentration gradient
basolateral transport for monosaccrides? active? up or down gradient?
GLUT2 - for all (glucose, fructose, galactose)
facilitated diffusion
down a gradient
protein digestion phases (3)? what each phase yields?
gastric - acid –> denatures; pepsin –>large polypeptides
pancreatic - enzymes (trypsin,ect) –> free aa + oligopeptides (2-8 aa’s long)
intestinal @ brush border –> free aa’s + di/tri peptides
agents in gastric digestion on protein?
acid denatures proteins
pepsinogen –> pepsin (via pH) breaks proteins down into large peptides + free aa (15% of digestion)
pancreas proteases?
trypsin
chymotrypsin
elastase
carboxypeptides
brush border aminopeptidases function?
break oligopeptides from pancreas proteases into free amino acids and di/tripeptides
di/tri peptides can be absorped (unlike di/tri-saccrides
what actives pepsinogen? what action does it have?
acid from gastric juice
attacks interior peptide bonds to make large peptide fragments (and a few free aa’s)
pancreatic phase - what initiates phase?
peptides, aa, proteins, fatty acids cause CCK release; acid cause secretin release
CCK stimualtes acinar cells to release 5 major proteases in inactive form – activated by enterokinase (trypsin which activates others)
small intestine phase - what happens?
aminopeptidases in brush border creates free aa’s
most absorption is of free aa and a few di/tri-peptides
protein digestion – small intestine phase - what happens? what can be absorped?
aminopeptidases in brush border creates free aa’s
most absorption is of free aa and a few di/tri-peptides
how are di/tri-peptide transported into enterocytes? what happens once they are in the enterocyte?
single transporter with broad specificity via H co-transport
broken down into free aa once in cell via peptidases
how do aa leave enterocycte?
facilitated carrier down a concentration gradient
are intact proteins ever absorbed? when? importance?
yes, a very small amount
infancy (and via M cells in adults)
important for passive immunity development via absorption of IgG from maternal milk
how are amino acids transported into enterocytes?
majority is Na dependent indirect manner with specific co-transporters (some Na independent)
specific for types of aa’s transported (charge)
