PROTEINS Digestion and Absorption Flashcards
After proteins are digested and chewed, do salivary glands contribute digestive enzymes?
NO!
What initiated protein digestion and where?
Acid pH and pepsin released in the STOMACH
What hydrolyze peptide bonds (remove N and C terminal aa’s) to form oligo, tri, dipeptides and amino acids?
Pancreatic proteases
What do brush border peptidases produce? How are the products absorbed?
Amino acids, tripeptides and dipeptides. Via specific secondarily active transporters
This amino acid is essential energy and growth requirement for small intestinal epithelial cells (enterocytes)
Glutamine (and glutamate). They are absorbed and utilized
Amino acids and di/tripeptide absorption at the brush border of small intestine has two important requirements
- co-absorption with Na and H2O
2. absorption is isosmotic
How does the linked transport of absorption of amino acids and di/tripeptides work?
- initial influx achieved by proton co transport
- proton expelled back into lumen in exchange for sodium
- no net change in protons
Pancreas secretes____ into the ____ to break up proteins into ____
pro-peptidases (endo and exopeptidases), duodenum, oligopeptides and some AA
Endopeptidases (3)
trypsin, chymotrypsin, and elastase
Exopeptidases (2)
carboxypeptidase, aminopeptidase
Mucosal thickness is dependent on ______
nutrient intake
How can we supply enough Na+ to absorb nutrients?
We need to recirculate Na
What region of the villa reabsorb amino acids and carbohydrates?
The villus tip! The villa structure is not a means to expand the resorptive surface
The villous tip has a PO2 of about 10 mmHg and no 100 that is actually should have like seen in vessels. Explain why and the advantage and disadvantage
O2 flows up to try and get to top but diffuses according to concentration gradient into interstitial space and enter the venous side.
Living in less oxygenated environment—
good since toxins are around and reduces amount of reactive oxygen species.
bad if there’s an ischemic even, then tip will suffer very quickly
The nutrients are exported from the absorptive cells via specific transporters and diffuse into the capillaries at the ______
villus tip!
How do Na and protons re-circulate back into the fluid sace?
between the absorptive cell and the unstirred mucus layer
What is essential in the absorption of vitamin B12, zinc, bile salts, and vitamin K?
The terminal ileum
Calcium is absorbed by active/passive transport in the ____ and is dependent on _____
ACTIVE transport in duodenum, vitamin D (induces transporter)
Magnesium is absorbed mostly in the _____ and ______
ileum and colon
Se, B12, and fat soluble vitamin K are mostly absorbed in the ____
terminal ileum
Where is folate, other members of B complex, and Vitamin C reabsorbed?
Proximal small intestine
What inhibit Zn?
Phytates (antioxidant components found in whole grains, legumes etc.)
Name 6 important vitamins/minerals that get absorbed by the terminal ileum
- Vitamin B12
- Vitamin K
- Zinc
- Selenium
- Bilt salt absorption
- Magnesium
The villous structure is necessary for an establishment of an osmotic gradient for effective absorption of nutrients. Explain the difference in osmolality at the base vs. at the villus tip
At base: isosmotic conditions necessary for efficient water and solute absorption
At tip: high osmolality