Week 3: Amino Acid Digestion & Absorption Flashcards
What must happen to proteins for them to be absorbed?
digested into amino acids
Amino acid chemical structure
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What hydrolyzes a peptide bond?
Proteases
Describe a peptide bond
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Where do proteases come from?
Synthesized and secreted by the pancreas due to CCK stimulation
What is the primary protease from the pancreas?
Trypsinogen
Describe the function of trypsinogen
is inactive when secreted from the pancreas
Is activated by?
Trypsinogen -enterokinase (enteropeptidase)-> Typsin
Trypsinogen is activated by?
Enterokinase (enteropeptidase)
Enterokinase AKA
Enteropeptidase
Enteropeptidase AKA
Enterokinase
Where is Enterokinase located?
transmembrane protein on the intestinal luminal membrane to prevent activation of trypsinogen into trypsin in a location where it could cause damage to cells
What is an endoprotease?
cleaves a peptide internally away from the ends
What is an exoprotease?
Cleaves a peptide on the ends
What is a zymogen?
exo or endoproteases that are inactive but can become activated by enterokinases
Enterokinase function
Activates all proteases or zymogens to their active form
How do Amino acids get into cells?
amino acids are polar and therefore can’t diffuse through membranes
They use Na+AA symporters driven by Na+K+ ATPase to provide the concentration gradient of Na+ needed to pull AAs into the enterocytes
Negatively charged AAs
Glutamate
Aspartic acid
Positively charged AAs
Histidine (very pH dependent)
Argynine
Lysine
Hydrophobic AAs
- glycine (Gly)
- alanine (Ala)
- valine (Val)
- leucine (Leu)
- isoleucine (Ile)
- proline (Pro)
- phenylalanine (Phe)
- methionine (Met)
- tryptophan (Trp)
Polar AAs
- serine (Ser)
- threonine (Thr)
- cysteine (Cys)
- asparagine (Asn)
- glutamine (Gln)
- tyrosine (Tyr)
Classes of AA transporters
- positively charged transporters
- negatively charged transporters
- aromatic transporters
- hydrophobic transporters
- di + tri-peptide transporters
What are brush border peptidases?
located on the brush-border luminal surface and assist in digesting di or tri peptides