130b carb and protein metabolism

Question 1

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

Answer 1

fructose

monosacc = FGG

Question 2

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)?

Answer 2

amino acids OR di/tri-peptides

simple monosaccarides (fructose, glucose, galactose)

Na-cotransport for monosacc and aa
H+ cotransport for di/tri peptides

Question 3

what type of carb are refined sugars found in the diet?

what are the 3 types and what are they made of?

Answer 3

disaccharides

sucrose (table sugar)= glucose + fructose

Maltose = 2 glucose

Lactose=glucose + galactose

Question 4

carb digestion in mouth - what does it? what bond does it break? what is left over?

Answer 4

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

Question 5

Once oligosaccharides reach the small intestine, where are things that break them down located? by what?

Answer 5

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

Question 6

where are carbs absorbed in the small intestine?

Answer 6

duodenum and upper jejunum

Question 7

what transports glucose and galactose into enterocytes? ATPase?

Answer 7

SGLT1 carrier - sodium dep glucose transporter

Not an ATPase, uses gradient for Na/K ATPase

Question 8

high fructose corn syrup

Answer 8

50% sucrose
50% fructose

sweeter than sugar and much cheaper

Question 9

fructose transportation into enterocytes? active? up or down gradient?

Answer 9

GLUT5 carrier

doesn’t require E

down a concentration gradient

Question 10

basolateral transport for monosaccrides? active? up or down gradient?

Answer 10

GLUT2 - for all (glucose, fructose, galactose)

facilitated diffusion

down a gradient

Question 11

protein digestion phases (3)? what each phase yields?

Answer 11

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

Question 12

agents in gastric digestion on protein?

Answer 12

acid denatures proteins

pepsinogen –> pepsin (via pH) breaks proteins down into large peptides + free aa (15% of digestion)

Question 13

pancreas proteases?

Answer 13

trypsin
chymotrypsin
elastase
carboxypeptides

Question 14

brush border aminopeptidases function?

Answer 14

break oligopeptides from pancreas proteases into free amino acids and di/tripeptides

di/tri peptides can be absorped (unlike di/tri-saccrides

Question 15

what actives pepsinogen? what action does it have?

Answer 15

acid from gastric juice

attacks interior peptide bonds to make large peptide fragments (and a few free aa’s)

Question 16

pancreatic phase - what initiates phase?

Answer 16

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)

Question 17

small intestine phase - what happens?

Answer 17

aminopeptidases in brush border creates free aa’s

most absorption is of free aa and a few di/tri-peptides

Question 18

protein digestion – small intestine phase - what happens? what can be absorped?

Answer 18

aminopeptidases in brush border creates free aa’s

most absorption is of free aa and a few di/tri-peptides

Question 19

how are di/tri-peptide transported into enterocytes? what happens once they are in the enterocyte?

Answer 19

single transporter with broad specificity via H co-transport

broken down into free aa once in cell via peptidases

Question 20

how do aa leave enterocycte?

Answer 20

facilitated carrier down a concentration gradient

Question 21

are intact proteins ever absorbed? when? importance?

Answer 21

yes, a very small amount

infancy (and via M cells in adults)

important for passive immunity development via absorption of IgG from maternal milk

Question 22

how are amino acids transported into enterocytes?

Answer 22

majority is Na dependent indirect manner with specific co-transporters (some Na independent)

specific for types of aa’s transported (charge)