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Flashcards in 130b carb and protein metabolism Deck (22)

What is the only monosacchride OR amino acid that can be absorbed through facilitated diffusion without Na dependent transport?


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?


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?


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?



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)