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A&p2 > Digestion And Absorption Of Proteins > Flashcards

Digestion And Absorption Of Proteins Flashcards

1
Q

Protein digestion

A

Catabolic pathway

-Proteins are large polypeptides made up of Amino acids (AAs)
-AAs binds together by peptide bond
-The bond that is broken during digestion of Proteins
are called peptide bond

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2
Q

Protein digestion in the stomach: production of pepsin

A

-Chief cells → pepsinogen → activate → Pepsin

-Activation of Pepsinogen to pepsin requires an acidic environment
-Parietal cells → HCL → Decrease the pH → Acidic Environment 1.8-3.5 → stimulate the conversion of pepsinogen into pepsin
-↑pH → pepsin inactivated

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3
Q

Protein digestion in the stomach: function of pepsin

A

-Pepsin stimulates the conversion of pepsinogen into pepsin (=Auto activator)

-Pepsin converts large polypeptide → smaller polypeptides
-Targets aromatic amino acids → Break bonds on carboxyl side
-Tyrosine
-Phenylalanine
-Tryptophan

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4
Q

Source of bicarbonate

A

Mucosal cells

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5
Q

Function of bicarbonate

A

Neutralizes gastric acids

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6
Q

Bicarbonate stimulate by

A

Secretin

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7
Q

Source of CCK

A

I cells (duodenum, jejunum)

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8
Q

Functions of CCK

A

⬆️Contraction of the gallbladder
↑ Secretion of pancreatic Enzymes
↑Relaxation of the sphincter of Oddi

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9
Q

CCK stimulated by

A

Postprandial: fatty acids and amino acids entering the small intestine

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10
Q

Source of secretin

A

S cells (duodenum)

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11
Q

Functions of secretin

A

↑Pancreatic secretion of bicarbonate
↑Secretion of bile

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12
Q

Secretin stimulated by

A

Postprandial: ↑ gastric acid and fatty acids in the duodenum

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13
Q

Source of GIP

A

K cells (Duodenum, jejunum)

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14
Q

Functions of GIP

A

↑ Insulin secretion
↓ Secretion of gastric acid

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15
Q

GIP stimulated by

A

Postprandial: fatty acids, glucose, amino acids entering small intestine

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16
Q

GIP

A

“Glucose-dependent insulinotropic peptide”

“Gastric inhibitory polypeptide”

17
Q

Production of pancreatic processes

A

-CCK= Cholecystokinin
-Stimulate acinar cells to produce Proteases
-Relaxes the Sphincter of Oddi → ejection of the Proteases to the duodenum

-Proenzymes (Inactive)
-Trypsinogen
-Chymotrypsinogen
-Procarboxypeptidase
-Proelastase

18
Q

Activation of pancreatic proteases

A

-Enterokinase in the epithelial cells of the lumen → brush border enzyme → activate trypsinogen → trypsin

-Trypsin stimulates the activation of proenzymes

1) Trypsinogen → trypsin
2) Chymotrypsinogen → chymotrypsin
3) Procarboxypeptidase → carboxypeptidase (A&B)
4) Proelastase → elastase

19
Q

Function of pancreatic proteases: trypsin

A

-Small polypeptide → Cleave peptide bonds on the
carboxyl side where there are Lysine and Arginine → tripeptide, dipeptide

-Exception they cannot hydrolyze the bond if there is Proline next to Lysine or Arginine

20
Q

Function of pancreatic proteases: chymotrypsin

A

Small polypeptide→ same as pepsin → Cleave peptide bonds on the carboxyl side where there are Tyrosine, Phenylalanine, Tryptophan → tripeptide, dipeptide

21
Q

Function of pancreatic proteases: carboxypeptidase

A

Small polypeptide→ act on carboxyl end→ AA, dipeptide, tripeptide

22
Q

Function of pancreatic proteases: elastase

A

Small polypeptide→ act on carboxyl end → AA, dipeptide, tripeptide

23
Q

Brush border enzymes of small intestin

A

Dipeptidase

Aminopeptidase

24
Q

Location of brush border enzymes

A

-Enterocytes→ epithelial cell found in the small intestine

-Most of the absorption occurs in the small intestine

-Structural Modifications that increase surface area in the small intestine →↑Digestion and ↑Absorption
-Circular Folds
- Villi
-Microvilli
-Enterocyte → little cytoplasmic extensions → increase the surface area for chemical digestion and absorption → microvilli → high concentration of brush border enzymes

25
Q

Absorption of protein: apical membrane: transporters

A

-AA Transporters
-Dipeptide Transporters
-Tripeptide Transporters
-Na+ /H+ Antiporter

26
Q

Absorption of proteins: apical membrane: dipeptides and tripeptides uptake mechanism

A

-Dipeptide Transporters = H+ / Dipeptide cotransporter

-Tripeptide Transporters= H+ / Tripeptide cotransporter

-Dipeptide and tripeptide uptake is an active process driven by a proton gradient.
-Na+ /H+ Antiporter → brings in proton in exchange of Na+
-Proton used for the transportation of the Dipeptide and tripeptide→ Symport mechanism

27
Q

Absorption of proteins: apical membrane: AAs Uptake Mechanism

A

-AA Transporters = Na+ / AA cotransporter

-Na+/K+ / ATPase →↓Na+ in the enterocyte
-Na+/K+ ATPase on the basal membrane → pump 3 Na+ outand2K+ in+utilizinganATP→↓Na+ →Na+ in lumen&raquo_space; Na+ in the enterocyte → AAs follow Na+ from lumen to enterocyte
-Secondary active transport → Driving Force is sodium concentration gradient
-Sodium moves down its concentration gradient into the cell, taking AA
-AA move against its concentration gradient

28
Q

Absorption of proteins: enterocyte

A

Enzyme in the enterocyte → Intracellular Peptidase cleave dipeptide, tripeptide → AAs

29
Q

Absorption of proteins: basolateral membrane

A

-Transporter: AA transporters

-Mechanism:
-AAs move out of the cell through Facilitated diffusion mechanism → capillaries → veins → hepatic portal vein → liver
-In the liver the AAs → Protein Synthesis
-↑ Insulin release in the fed state → Enhance protein
synthesis and AAs Uptake

30
Q

Pepsinogen

A

Activating agent: enteropeptidase and trypsin

Active enzyme: pepsin

Location: stomach

Function: cleaves bonds involving Phenylalanine, Tyrosine, and Tryptophan

Product: peptides, oligopeptides

31
Q

Trypsinogen

A

Activating agent: enteropeptidase and trypsin

Active agent: trypsin

Location: pancreas secretion to Duodenum

Function: cleaves bonds of the C-terminal of Lysine and Arginine

Product: tripeptide, dipeptide

32
Q

Chymotrypsinogen

A

Activating agent: trypsin

Active enzymes: chymotrypsin

Location: pancreas secretion to Duodenum

Function: cleaves bonds involving Phenylalanine, Tyrosine, and Tryptophan

Product: tripeptide, dipeptide

33
Q

Pro-elastase

A

Activating agent: trypsin

Active enzyme: elastase

Location: pancreas secretion to Duodenum

Function: Cleaves bonds, from C-Terminal

Product: AAs, tripeptide, dipeptide

34
Q

Pro-carboxypeptidase

A

Activating agent: trypsin

Active enzyme: carboxypeptidase (A, B)

Location: pancreas secretion to Duodenum

Function: cleaves bonds from C-Terminal

Product: AAs, dipeptide, tripeptide

35
Q

Aminopeptidase

A

Location: intestinal mucosa

Function: Cleaves unspecific end AAs from N- terminal

Product: AAs

36
Q

Dipeptidase

A

Location: intestinal mucosa

Function: cleaves dipeptides

Product: AAs

A&p2 (28 decks)

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