PROTEINS Digestion and Absorption

Question 1

After proteins are digested and chewed, do salivary glands contribute digestive enzymes?

Answer 1

NO!

Question 2

What initiated protein digestion and where?

Answer 2

Acid pH and pepsin released in the STOMACH

Question 3

What hydrolyze peptide bonds (remove N and C terminal aa’s) to form oligo, tri, dipeptides and amino acids?

Answer 3

Pancreatic proteases

Question 4

What do brush border peptidases produce? How are the products absorbed?

Answer 4

Amino acids, tripeptides and dipeptides. Via specific secondarily active transporters

Question 5

This amino acid is essential energy and growth requirement for small intestinal epithelial cells (enterocytes)

Answer 5

Glutamine (and glutamate). They are absorbed and utilized

Question 6

Amino acids and di/tripeptide absorption at the brush border of small intestine has two important requirements

Answer 6

1. co-absorption with Na and H2O

2. absorption is isosmotic

Question 7

How does the linked transport of absorption of amino acids and di/tripeptides work?

Answer 7

• initial influx achieved by proton co transport
• proton expelled back into lumen in exchange for sodium
• no net change in protons

Question 8

Pancreas secretes____ into the ____ to break up proteins into ____

Answer 8

pro-peptidases (endo and exopeptidases), duodenum, oligopeptides and some AA

Question 9

Endopeptidases (3)

Answer 9

trypsin, chymotrypsin, and elastase

Question 10

Exopeptidases (2)

Answer 10

carboxypeptidase, aminopeptidase

Question 11

Mucosal thickness is dependent on ______

Answer 11

nutrient intake

Question 12

How can we supply enough Na+ to absorb nutrients?

Answer 12

We need to recirculate Na

Question 13

What region of the villa reabsorb amino acids and carbohydrates?

Answer 13

The villus tip! The villa structure is not a means to expand the resorptive surface

Question 14

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

Answer 14

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

Question 15

The nutrients are exported from the absorptive cells via specific transporters and diffuse into the capillaries at the ______

Answer 15

villus tip!

Question 16

How do Na and protons re-circulate back into the fluid sace?

Answer 16

between the absorptive cell and the unstirred mucus layer

Question 17

What is essential in the absorption of vitamin B12, zinc, bile salts, and vitamin K?

Answer 17

The terminal ileum

Question 18

Calcium is absorbed by active/passive transport in the ____ and is dependent on _____

Answer 18

ACTIVE transport in duodenum, vitamin D (induces transporter)

Question 19

Magnesium is absorbed mostly in the _____ and ______

Answer 19

ileum and colon

Question 20

Se, B12, and fat soluble vitamin K are mostly absorbed in the ____

Answer 20

terminal ileum

Question 21

Where is folate, other members of B complex, and Vitamin C reabsorbed?

Answer 21

Proximal small intestine

Question 22

What inhibit Zn?

Answer 22

Phytates (antioxidant components found in whole grains, legumes etc.)

Question 23

Name 6 important vitamins/minerals that get absorbed by the terminal ileum

Answer 23

1. Vitamin B12
2. Vitamin K
3. Zinc
4. Selenium
5. Bilt salt absorption
6. Magnesium

Question 24

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

Answer 24

At base: isosmotic conditions necessary for efficient water and solute absorption

At tip: high osmolality