Mucosal Absorption I

Question 1

define absorption

Answer 1

process of translocating basic molecules from intestinal lumen through epithelium into vascular system

Question 2

the end products of CHO and protein digestion are ___

Answer 2

hydrophilic

Question 3

what’s the most important active transporter in GI?

Answer 3

Na/K ATPase

Question 4

secondary active transport requires use of the ___ gradient

Answer 4

Na+

Question 5

what types of transport is secondary active?

Answer 5

co-transport - aka ligands are on the same site
anti-porter/exchanger - ligands are on opposite sites

Question 6

in secondary active co-transport, what happens once Na is bound to the transporter?

Answer 6

conformation change “delivers” ions and molecule into cell

Question 7

which type of secondary active transport is SLUT GLUT?

Answer 7

co-transport

Question 8

which type of secondary active transport is Na/H?

Answer 8

anti-porter/exchanger

Question 9

Na/H transport creates the ___ gradient

Answer 9

H+

Question 10

Na/K pump maintains ___ gradient

Answer 10

Na+

Question 11

intracellular H+ is transported out by ___ antiport driven by which gradient?

Answer 11

Na/H
Na+ gradient

Question 12

what is the teritiary active transport?

Answer 12

Cl/bicarb exchange

Question 13

what does CA do?

Answer 13

catalyzes H+ and bicarb production
(tertiary active)

Question 14

what are the three types of passive diffusion?

Answer 14

transcellular absorb
paracellular absorb
facilitated diffusion

Question 15

what is transcellular absorption?

Answer 15

ions follow electrochemical gradient through ion channels in apical membrane

Question 16

what is paracellular absorption?

Answer 16

ions follow electrochemical gradient and osmotic P through tight junctions

Question 17

what is facilitated diffusion?

Answer 17

spontaneous passive diffusion of molecules/ions across membrane via specific transmembrane proteins

Question 18

where are glc co-transporters located?

Answer 18

next to glycocalyx enzymes on apical membrane

Question 19

how is fructose internalized?

Answer 19

facilitated diffusion
based on gradient

Question 20

glc movement through basolateral space is driven by…

Answer 20

diffusion

Question 21

water follows ___

Answer 21

SOLUTES

Question 22

the concept of water following solutes is referred to as…

Answer 22

iso-osmolar absorption

Question 23

what is used for oral rehydration therapy if the SI is still in tact?

Answer 23

SLUT GLUT - administer fluids with glc/electrolytes so slut glut gets put to use

Question 24

SLUT GLUT stimulates water absorption by ___

Answer 24

solvent drag

Question 25

what mechanism stays in tact in patients with D disorders?

Answer 25

SLUT GLUT solvent drag

Question 26

CHO digestion/absorption pathophysiology is mostly due to ___ deficiency that ___ breakdown

Answer 26

enzyme prevents breakdowns

Question 27

what happens if you have unabsorbed CHO?

Answer 27

hold water osmolarity and cause osmotic D

Question 28

what occurs at apical membrane regarding protein digestion? (what transporters)

Answer 28

aa co-transport (Na) four co-transport - neutral aa, dibasic aa, dicarboxylic aa, imino/proline aa peptide carrier (H transport) peptides further digested by intracellular enzymes

Question 29

what occurs at basolateral membrane regarding protein digestion?

Answer 29

release to extracellular space as free aa facilitated diffusion

Question 30

how does protein absorption occur during first 24hrs of life?

Answer 30

endocytosis of entire proteins and Ig's receptor mediated, unspecific done via specialized enterocytes that disappear after ~24hrs

Question 31

how does aminoaciduria develop?

Answer 31

develops from congenital defect in transport of specific aa may still be able to do absorption of di/tri-peptides

Question 32

what is cysinuria?

Answer 32

type of aminoaciduria transporter for dibasic aa (cystine, lysine, arginine) is ABSENT from or reduced in gut/kidney dibasic aa lost in urine/feces can lead to cystine stones

Question 33

what facilitates lipid digestion/absorption?

Answer 33

micelles

Question 34

how does lipid absorption occur?

Answer 34

micelle comes close to enterocyte surface and contents diffuse into cell except for bile acids which remains in intestinal lumen

Question 35

the concentration gradient ___ passive diffusion of micellar products

Answer 35

favors

Question 36

how much ingested fat is removed by SI?

Answer 36

95%

Question 37

what are the intracellular events of lipid absorption? (two paths)

Answer 37

lipids reassemble in cells (form triglyceride) MONOGLYCERIDE ACYLATION PATH PHOSPHATIDIC ACID PATH chylomicrons

Question 38

describe the monoglyceride acylation pathway of lipid intracellular absorption

Answer 38

2 mono + fatty acid acyl CoA = triglyceride

Question 39

describe the phosphatidic acid pathway of lipid intracellular absorption

Answer 39

glycolysis -> P-glycerol or diOH-acetone P -> alpha-glycerolP -> triglycerides

Question 40

what are chylomicrons?

Answer 40

core of triglyceride and cholesterol surrounded by phospholipase and apoproteins aka transport vesicle for lipids in lacteals

Question 41

what are lacteals?

Answer 41

lymphatic vessels of SI villi that absorb digested fats

Question 42

water soluble chylomicrons ___ phospholipids, triglycerides, proteins

Answer 42

coat

Question 43

describe the process of chylomicron assembling?

Answer 43

1. fa, monoglyceride converts into triglycerides in ER 2. cholesterol is re-esterified 3. triglycerides ad cholesterol are packaged into chylomicrons 4. apoproteins are embedded in chylomicrons

Question 44

what are apoproteins?

Answer 44

structural components of lipoprotein particles ligand for cell surface receptors

Question 45

without apoproteins, large quantities of triglycerides would accumulate where?

Answer 45

enterocytes

Question 46

what are the five lipoprotein vehicles?

Answer 46

chylomicrons VLDL IDL LDL HDL

Question 47

chylomicrons are taken up by...

Answer 47

lacteals

Question 48

where do lacteals drain?

Answer 48

into cisterna chyli (abdomen duct) then thoracic duct lastly, internal jugular vein

Question 49

bile acids remain in the ___.

Answer 49

intestinal lumen

Question 50

what happens regarding lipids if there is a lack of bile acids?

Answer 50

unable to digest fats

Question 51

where is the bile acid transporter located and what is it called?

Answer 51

in ileum Na-bile acid-cotransport

Question 52

are bile acids recycled?

Answer 52

YES, returns to portal system

Question 53

what is enterohepatic circulation?

Answer 53

refers to the process of bile acid recycling, storage, and release into SI lumen

Question 54

bile acids are synthesized from ___ in the liver

Answer 54

cholesterol

Question 55

which vein takes bile acids back to the liver?

Answer 55

portal vein

Question 56

where do bile acids go if NOT recycled into the liver?

Answer 56

show up in blood plasma

Question 57

are liver shunts acquired or congenital?

Answer 57

can be BOTH

Question 58

how does a patient acquire a liver shunt?

Answer 58

liver disease

Question 59

which species most likely gets extra-hepatic liver shunts?

Answer 59

small and toy breeds

Question 60

which species most likely gets intra-hepatic liver shunts?

Answer 60

large breed dogs

Question 61

what are body affects of liver shunts?

Answer 61

poor growth/development neurologic changes behavior change increased thirst, frequent urination V accumulation of toxins and metabolic waste products can lead to HEPATIC ENCEPHALOPATHY

Question 62

what is hepatic encephalopathy?

Answer 62

neurological disturbances in patients with liver dysfunction (shunt) caused by effects on brain of substances that under normal circumstances are efficiently metabolized by liver

Question 63

what does a bile acid test do?

Answer 63

liver function test indicates degree of inflammation/damage

Question 64

what does it mean if the bile acid test comes back normal?

Answer 64

low initial AND low 2hrs levels of bile acid

Question 65

what does it mean if the bile acid test is elevated at rest?

Answer 65

bile acids remain in circulation (shunt, liver disease, gallbladder issue, etc)

Question 66

what does it mean if the bile acid test has normal resting level but elevated 2hrs levels?

Answer 66

bile acids are very slowly reabsorbed and escape into systemic circulation