7. Digestion Flashcards
salivary α-amylase digests glycogen and starch yielding
dextrins- short branched
digests dextrin into disaccharides
pancreatic α-amylase
disaccharidases are found in
brush border
majority of monosaccharide absorption occurs in
duodenum and
upper jejunum
glucose and galactose are transported into enterocytes via
secondary active transport - protein SGLT
- with the Na ion
- require ATP
Fructose is absorbed via
FACILITATED DIFFUSION
GLUT-5
transport protein for galactose and glucose to enterocyte
SGLT
•no ATP required
transport protein for fructose to enterocyte
GLUT 5
how is glucose, galactose, and fructose are all transported from
from basement membrane of enterocyte ≈> PORTAL CIRCULATION
- GLUT 2
* facilitated diffusion
why is CELLULOSE excreted unchanged?
it contains ß-glycosidic bonds
•cannot be digested by α-glycosidases
is there carb digestion in stomach
- none
* low pH inhibits salivary amylase
is there lipid digestion in the oral cavity
none
enzymes in small intestines to digest carbs
pancreatic α-amylase
disaccharidases
acid-stable lipase
lingual lipase
gastric lipase
digest TAGs containing short and medium chain FA
lingual lipase
gastric lipase
emulsification of lipids through bile salts and peristalsis occurs in the
duodenum
digests TAGs into 2-monoacylglycerols and 2 free FA
Pancreatic lipase
digests cholesteryl esters into cholesterol and FA
cholesteryl ester hydrolase
requires colipase to fx
pancreatic lipase
factors for digestion of lipids in the small intestines
- bile salts, peristalsis
- pancreatic lipase + colipase
- cholesteryl esters
requires to form disk-shaped mixed micelles to be absorbed
- free FA
- cholesterol
- 2-monoacylglycerol
- fat-soluble vitamins
not requierd to form disk-shaped mixed micelles to be absorbed
SHORT AND MEDIUM-CHAIN FA
bile salts are reabsorbed in the
terminal ileum (enterohepatic circulation)
•in this organelle of enterocytes, the dietary lipids are converted back
to TAGs and cholesteryl esters
endoplasmic reticulum
•in this ER of enterocytes the dietary lipids are converted back
to TAGs and cholesteryl esters
exported as
chylomicrons and released into lymphatic circulation (lacteals )
this FA bind to albumin and go to portal circumaltion
short- and medium chain FA
HCl is secreted by
parietal cells
this chemical is required to convert pepsinogen to pepsin
HCl
pepsinogen is secreted by
chief cells
- located on the brush border
* releases free amino acids from dipeptides and oligopeptides
aminopeptidases
this activates trypsinogen
enteropeptidase
zymogen released in the small intestine
trypsinogen
chymotrypsinogen
proelastase
procarboxypeptidase
Free amino acids are absorbed via
SECONDARY ACTIVE TRANSPORT
•coupled with Na+
di- and tripeptides are absorbed via
H+ linked transport system
from enterocytes , free amino acids are taken to the portal circulation via
FACILITATED DIFFUSION
