Wold 2 Flashcards
There are 5 basic categories of useable food (energy sources
Carbohydrates Protein Fats Vitamins Minerals
The brush border ectoenzymes are essential for
digestion and absorption of carbohydrates
Complex carbohydrates broken down into
monosaccharides Digestive enzymes (such as amylase) Ectoenzymes (lactase)
Monosaccharides taken up by epithelial cells by
transporters
Monosaccharides passed into blood via
GLUT2
Proteins are broken down into peptides in
2 locations
Stomach
———- is produced in stomach—cleaved to —— which degrades protein
Pepsinogen
pepsin
Small Intestine
Pancrease releases
pro-enzymes into small intestine to digest proteins
Pancreas pro enzymes
Trypsinogen
Cymotrypsinogen
Procarboxypeptidases A and B
Proelastase
Must be converted to active enzymes—initiated by enteropeptidase
Trypsin is an ——- for cleavage of proteins
essential protease
Two Broad Classes of AA Transporters
Na+ Dependent
Na+ Independent
AA Subclasses are specific for
certain types of amino acids
AA Transporters are on
brush border and basolateral membrane
Sources of Lipase
Lingual Lipase
Gastric Lipase
Pancreatic Lipase
But, then how does lipase interact with the fat?
Colipase
How do micelles enhance absorption of fatty acids?
Micelles are in equilibrium with free fatty acids.
Micelles are constantly breaking down and reforming.
Triglycerides are found in
systemic circulation, not free fatty acids or monoglycerides.
Many vitamins are fat soluble
A
D
E
K
vitamins
Solubilized in
micelles, and passively diffuse through intestinal epithelial cells
Vitamins
Released into body with
chylomicrons
Water soluble vitamins
All are absorbed by
facilitated or active transport, except B12
All of the proteases are released as
proenzymes
Luminal peptidases are not
sufficient to breakdown protein; brush border enzymes are also needed
Peptides and amino acids are
transported across epithelial cells by transporters
Fatty acid absorption occurs in the
small intestine (primarily duodenum), but digestion occurs in stomach and duodenum
Fats are not water soluble, but
lipases are.
Gastric emptying is slowed by
fats
Fat films are emulsified both
Mechanically
Emulsifying agent
Most water absorption occurs in the
small intestine
Much of the concentration gradient of solutes is dependent upon
Na+
Absorption of Na+
Occurs throughout the
entire GI tract
Absorption of Na+
Can occur against a
small electrochemical gradient
Absorption of Na+
Is highest in areas where
glucose and galactose or amino acids are being transported
Absorption of Na+
Cl-, HCO3, K+ are also absorbed in part due to
Na+
Absorption of Minerals (Ca++)
Actively absorbed by
all segments of the intestine
Absorption of Minerals (Ca++)
Salts are soluble at
low pH
Absorption of Minerals (Ca++)
Strongly enhanced by
vitamin D
Absorption of Fe++
Very
inefficient (< 10% of dietary Fe++ is absorbed)
Absorption of Fe++
Stomach ——– absorption
enhances
Absorption of Fe++
======can not be absorbed
Fe+++
