L20: AA Metabolism (may) Flashcards
What is Kwashiorkor?
A severe form of protein malnutrition
What are the effects of Kwashiorkor?
- Muscle wasting
- Decreases the body’s ability to produce digestive enzymes and new intestinal epithelial cells.
- osmotic imbalance in the GI system
What does osmotic imbalance in the GI system lead to?
Gut swelling (edema or retention of water)
What is the aim of digestion of dietary proteins?
To hydrolyze proteins into di- and tri- peptides and free amino acids.
Where does the digestion of proteins begin and end?
it starts in the stomach and ends in the small intestine.
Proteolytic enzymes are produced by?
- Stomach
- Pancreas
- Small intestine
What is HCl secreted by?
parietal cells of the stomach
HCL is too dilute (pH 2-3) to hydrolyze proteins, therefore it functions to…
denature proteins and kill some bacteria
my explanation: 3shan y5aleehum more susceptible to subsequent hydrolysis by proteases
What is pepsin?
an endopeptidase
which hydrolyses protein to polypeptides
What is pepsin secreted by? as what?
Secreted by the chief cells as an active zymogen: pepsinogen
shnu zymogen
an inactive enzyme
Pepsinogen is activated to pepsin by?
- HCL (low pH)
2. Autocatalytic activation (by other pepsin molecules)
What is the function of pepsin?
it releases peptides and a few free amino acids from dietary proteins
The release of pancreatic zymogens are mediated by?
2 digestive tract hormones:
- Cholecytokinin
- Secretin
How are pancreatic zymogens activated?
A duodenal enteropeptidase (aka enterokinase) converts the pancreatic zymogen trypsinogen to trypsin
shnu trypsin?
It is the common activator of all other pancreatic zymogens
“trypsin cleaves ONLY after arganine or lysine?” this statement proves what?
that each enzyme has a different specificity for the amino acid
What is an aminopeptidase?
Exopeptidase
an enzyme that removes an amino acid from the end with a free amino group
where can you find aminopeptidase?
on the luminal surface of the intestine
what is the function of an aminopeptidase?
it repeatedly cleaves the N-Terminus residue from oligopeptides –> to produce even smaller peptides and free amino acids
Free AA are absorbed by?
intestinal enterocytes by a Na+ linked secondary transport system
Di- & Tri- peptides are absorbed by?
H+ linked transport system
Free AA are released into?
the general circulation by a facilitated transporter
Free AA are metabolised in the?
liver
