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Physl Part 2 > GI 17 > Flashcards

GI 17 Flashcards

1
Q

In addition to dietary intake, where does the intestine also receive large amounts of protein?

A

In mucus, enzymes and degraded epithelial cells

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2
Q

What do polypeptide chains need to be broken down into?

A

Individual amino acids

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3
Q

What is protein digestion mainly mediated by?

A

Proteolytic enzymes (proteases)

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4
Q

Why are many enzymes secreted as inactive precursors?

A

to protect the cells where they are manufactured because they are very powerful

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5
Q

What are the two categories of Protease enzymes?

A
  • Endopeptidases

* Exopeptidases

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6
Q

Where do Endopeptidases cleave proteins?

A

At interior peptide bonds

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7
Q

What are examples of endopeptidases?

A
  • Trypsin
  • Chymotrypsin
  • Elastase
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8
Q

Where do Exopeptidases cleave proteins?

A

At their n- (aminopeptidases) and c-termini (carboxypeptidases)

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9
Q

Where does Protein digestion begin?

A

In the stomach

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10
Q

What does the highly acidic environment of the stomach do to proteins?

A

Denatures them

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11
Q

What cleaves large polypeptides in the stomach?

A

Pepsin

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12
Q

What is the inactive precursor to Pepsin and how does it get activated?

A

Pepsinogen and it is activated by gastric acid

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13
Q

Why does pepsin stop working in the duodenum?

A

Because it requires acidic activity and the duodenum is more alkaline than the stomach

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14
Q

What proteases contribute to intestinal protein digestion?

A
  • Pancreatic enzymes

* Intestinal brush border enzymes

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15
Q

What are the pancreatic enzymes that digest proteins activated by?

A

Enterokinase and Trypsin

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16
Q

How does Enterokinase and Trypsin activate protein digesting pancreatic enzymes?

A

Enterokinase on the surface of intestinal epithelial cells cleave trypsinogen into the active trypsin. Trypsin then catalyzes the activation of the other inactive precursors and more trypsin

17
Q

What are some intestinal brush border enzymes that digest proteins?

A
  • Aminopeptidases
  • Carboxypeptidases
  • Endopeptidases
18
Q

What do the activity of the brush border enzymes generate?

A
  • Individual amino acids
  • Dipeptides
  • Tripeptides
19
Q

What happens to Dipeptides and Tripeptides?

A

They can be taken up into intestinal epithelial cells and are further broken down in the cytosol to produce individual amino acids

20
Q

What are the three locations that protein digestion can occur?

A
  • Intestinal lumen
  • Intestinal brush border
  • Inside intestinal epithelial cell
21
Q

What are the products of protein digestion?

A
  • Amino acids
  • Dipeptides
  • Tripeptides
22
Q

What does absorption of protein digestion products require?

A

Uptake and transit through the intestinal epithelium

23
Q

What are small peptides (di and tripeptides) taken up into epithelial cells by?

A

A transport protein called PepT1 through secondary active transport

24
Q

What kind of transport are small peptides (di and tripeptides) taken up into epithelial cells by?

A

Secondary active transport

25
Q

What happens once small peptides (di and tripeptides) are taken into epithelia cells?

A

They are cleaved by intracellular peptidases into amino acids

26
Q

How do amino acids exit epithelial cells?

A

By facilitates diffusion through amino acid transporters

27
Q

What does PepT1 do?

A

Brings small peptides (di and tripeptides) into the epithelial cell along with H+ using secondary active transport

28
Q

What is the proton gradient for the secondary active transport of small peptides (di and tripeptides) maintained by?

A

The sodium hydrogen exchanger (NHE) that brings sodium into the cell and H+ out of the cell

29
Q

What is the sodium gradient for the secondary active transport of small peptides (di and tripeptides) maintained by?

A

A basolateral Sodium potassium ATPase

30
Q

How many transport mechanisms are there that facilitate amino acid uptake into intestinal epithelial cells?

A

At least seven

31
Q

What do the transport mechanism that bring amino acids into the epithelial cells rely on?

A

Sodium ion gradients

32
Q

How do amino acids enter the cell?

A

By secondary active transport coupled to a gradient of sodium ions

Physl Part 2 (96 decks)

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