GI Digestion and Absorption Flashcards
About ______ percent of proteins are digested by gastric pepsin.
15
Luminal peptidases and brush-border enzymes break down _______________.
proteins into dipeptides, tripeptides, and amino acids
Intracellular peptidases within enterocytes break down ____________. This prevents the need for basolateral polypeptide transporters.
dipeptides and tripeptides to amino acids
The major uptake route for amino acids is ______________.
sodium cotransport (from the Na/K ATP pump gradient)
Infants utilize ____________ to absorb proteins.
pinocytosis
Protons help ____________ get absorbed via cotransport.
dipeptides and tripeptides
The body can make all necessary lipids except _____________.
linoleic acid (omega-6 fatty acid) –which gets converted to arachidonic acid –and alpha-linoleic acid (omega-3 fatty acid)
What is steatorrhea?
Excessively greasy stool
The substance in lacteals is called ______________.
chyle
Most GI secretion occurs in the ___________, while most absorption occurs in the ____________.
stomach; jejunum
Potassium is absorbed ____________ in the jejunum and ______________ in the colon.
paracellularly; transcellularly
Vitamin D is first hydroxylated in the __________ and then again in the ______________.
liver; kidney
Iron can be absorbed as ___________.
Fe2+ or heme
Water absorption ___________ as you proceed from the small intestine to the large intestine.
decreases (because paracellular permeability decreases in the colon); in the distal colon, water absorption must be coupled to ion movement
Chloride channels are dependent on _____________.
cAMP
True or false: loperamide can treat cholera diarrhea.
False. Loperamide does not affect the diarrheal mechanism of cholera.
Maltose is __________.
a disaccharide of glucose
Elastase breaks down ______________.
neutral, aliphatic amino acids
True or false: fatty acids require co-transport to be absorbed.
False. They pass through the membrane.
What activates pepsinogen?
Low pH (1-3)
How are the pancreatic proteases terminated?
They digest themselves.
Cysteinuria is usually accompanied by __________.
loss of lysine, arginine, and ornithine (COAL); this results from loss of the Na-amino acid transporter, resulting in inability to absorb or excrete these molecules
Chylomicrons contain what three things?
Triglycerides, cholesterol, and phospholipids
Lipase and colipase form what?
Micelles that are passively absorbed
Water rapidly crosses the intestinal epithelium, so chyme ____________.
quickly becomes isotonic with the blood
By what receptors are proteins absorbed?
- Sodium cotransport
- Proton cotransport for di- and tripeptides
- Pinocytosis of peptides (only in infants)
- Sodium independent transport
What does lipase do?
It hydrolyzes triglycerides to free fatty acids.
Chylomicrons are synthesized in _________________.
intestinal epithelium
About _______ liters of fluid are secreted into the gut each day. All but about 100-200 mLs is reabsorbed.
9
In which part of the GI tract does sodium enter via ENaC?
The colon
