Gi--Physiology Of Absorption

Front 1

What does alpha amylase do?

Back 1

Cleaves starch only at 1,4 linkages(NOT at 1,6 or at the ends) so that no free glucose is made from starch digestion
Maltose, maltotriose, or limit dextrin is made

Front 2

True/False: Starch is broken down in the brush border.

Back 2

FALSE: It is broken down in the lumen by free alpha amylase(LUMINAL DIGESTION)

Front 3

Where are the disaccharides resulting from starch digestion broken down?

Back 3

In the brush border

Front 4

How are simple sugars absorbed?

Back 4

GLT1 sodium co-transporter(glucose/galactose) or through the GLUT5(fructose)

Front 5

Glucose and galactose enter enterocytes how?

Back 5

Using the sodium gradient set up by the Na/K ATPase in the apical membrane--they are secondarily actively transported into the cell through the GLUT1

Front 6

How do all sugars leave enterocytes?

Back 6

Through the GLUT2 transporter

Front 7

Trypsinogen is activated by what? What does it do?

Back 7

Enterokinase cleaves trypsinogen into trypsin--this cleaves all other pancreatic enzymes except pepsin

Front 8

What are the three methods for protein absorption?

Back 8

Secondary active transport coupled with sodium(may be multiple AA or just one type)
PepT1 Oligopeptide Transporter--this is the fastest and transports two to three AA peptides(KINETIC ADVANTAGE)
Endocytosis into enterocytes and M cells to present to lymphocytes in the lamina propria

Front 9

All protein transport types are in what class of cell transportation?

Back 9

Facilitated diffusion

Front 10

Which protein transport method is the best?

Back 10

Oligopeptide transport through the PepT1 transporter

Front 11

What is the process for fat absorption?

Back 11

Fat droplets in the stomach are coated in phospholipids and bile salts grab on them in the duodenum--The bile salts attract lipases which need bile salt and COLIPASE to stay attached--Lipase begins chewing off FFA and those are formed into lamellar vesicles which are bile salt coated and contain cholesterol, phospholipid, and FFA in the center--the lamellar vesicles attract more bile salts to become micelles--the micelles bump into enterocytes and their FFA are protonated--the protonated FFA's are taken up by the cell and the bile salts are reabsorbed in the ileum

Front 12

What is the order of fat objects in absoprtion?

Back 12

Emulsified droplet--Lamellar vesicle--Micelle--FFA in cell

Front 13

What happens once the FFA's are in the cell?

Back 13

FABP binds them and they are resynth. into TG's in the smooth ER
FA + CoA w/ ATP-->Acyl CoA + Monoglyceride = Diglyceride + Acyl CoA = TG

Front 14

What does lipase do?

Back 14

Breaks up TG into FFA

Front 15

What are cholymicrons and how are they made?

Back 15

Phospholipids, TG's, and cholesterol are packaged together and coated in apoproteins

Front 16

Where is cobalamin absorbed?

Back 16

ONLY IN THE ILEUM

Front 17

What is the process for Fe absorption?

Back 17

Heme oxygenase breaks down the heme in the enterocytes to yield free Fe--biliverdin(byproduct) is converted into bile salts and bilirubin--Mobilferrin takes up free Fe and exits at the BL membrane to bind TRANSFERRIN--transferrin is taken to the liver(it is also in the gut and grabs Fe and then is endocytosed in vesicles)

Front 18

What is DCT1 and what can it cause?

Back 18

DCT1 works with a PROTON gradient to facilitate Fe/H+ cotransport--hemachromatosis is caused by upreg of this transporter and is treated by phlebotomy