lec 2 Flashcards
defect in the intestinal A.A transport system are seen in inborn errors of metabolism
- HARTNUP DS
2. Cystinuria + slide 25
Peptide Absorption
More rapid than absorption of free A.A
• Active transport
Metabolized into free A.A in enterocyte
• Only free A.A absorbed into blood
Free Amino Acid Absorption
active transport Carrier systems • Neutral AA • Basic AA • Acidic AA • Imino acids
Absorption of Intact Proteins Newborns
– First 24 hours after birth
– Immunoglobulins
• Passive immunity
Absorption of Intact Proteins Adults
– Paracellular routes • Tight junctions between cells – Intracellular routes • Endocytosis • Pinocytosis
Enterokinase or enteropeptidase)
- Trypsinogen trypsin
* Trypsin then activates all the other enzymes
Dipeptidases
Cleave dipeptides into Aas
Aminopeptidases
Cleave at N-terminal AA
In the Enterocytes
• First cells that can use the amino acids –Transport into portal blood –Protein synthesis •Digestive enzymes • Structure and growth –Energy
Abnormalities in the protein digestion
and amino acid absorption
Defect in the pancreatic secreation.
Defective carrier system
Defect in the pancreatic secreation
Cystic fibrosis,
Cystic fibrosis,
,incomplete digestion of fat and protein,results in abnormal appearance of lipids (steatorrhea) and proteins in fece
Glycerol absorption short and medium chain fatty acids
directly absorbed from the intestinal lumen → portal vein → liver for further utilization
free cholesterol and βacyl glycerol absorption
Long chain fatty acids,
bile salts form mixed micelles.
Mixed micelles are
soluble in the aqueous environment of the intestinal lumen
monoglycerides and fatty acid
diffuse across the plasma membrane of the enterocyte.
NOT the micelles
Lysophospholipids are recycled to form
phospholipids
Cholesterol is re acylated to form
Cholesteryl esters
Long chain fatty acids are used for
esterification to form
TGs, phospholipids and cholesteyl esters.
Short and medium chain fatty acid are released in to
the portal circulation and are carried by serum albumin to liver.
1-monoacyglycerols are hydrolyzed to
fatty acids and glycerol
2-
monoacylglycerols are re-acylated
triacylglycerols via the monoacylglycerol pathway.
Lipid malabsorption results in
increased lipids
including fat soluble vitamins A,D E and K in the
feces.
Lipid Malabsorption(Steatorrhea) Cause
pancreatic insufficiency, including
cystic fibrosis , chronic diseases of pancreas or
surgical removal of pancreas
Shortened bowel, Celiac diseases, sprue or
crohn’s disease
May be bile duct obstruction due to gall stones,
tumor of head of pancreas, enlarged lymph nodes
etc.
Milk and coconut oil are used therapeutically
since they contain medium chain fatty acids
