Proteins Digestion and Absorption Flashcards
How digestive enzymes break down large molecules
Hydrolytic cleavage
Main areas of protein digestion
Stomach and small intestine
What theory do enzymes work by
Enzyme-substrate complex
Enzyme in lining of stomach
Pepsinogen. Inactive form of pepsin. Activated by change of pH when entering HCl, by changing of shape
Pepsin Outline
Endopeptidase (cuts peptide bonds in the middle of chain). Cleaves at hydrophobic amine side of aa
Enteropeptidase Location, Substrate and Product
Small intestine lining, trypsinogen and tripsin
Trypsin Location and formation
Enzyme enteropeptidase works on substrate trypsinogen
Chymotrypsin Location and Formation
Small intestine, enzyme trypsin works on substrate chymotrypsinogen
Elastase Location and formation
Small intestine, enzyme trypsin acts on substrate proelastase
Carboxypeptidase Location and function
Small intestine, enzyme trypsin acts on substrate procarboxypeptidase
Pancreatic Endopeptidases
Trypsin (basic aas) chymotrypsin (hydrophobic aas) and elastase (small aas)
Pancreatic carboxypeptidases
Carboxypeptidase A (hydrophobic aas) and Carboxypeptidase B (basic aas)
Enzymes at brush border
Aminopeptidase, endopeptidase, carboxypeptidase and dipeptidase
Protein Digestion Products
Tetrapeptides, tripeptides, dipeptides and amino acids
Main site of protein absorption
Small intestine (illeum), through endothelial cell lining
Small Intestine Unit of Absorption
Villus. Tubes of length 0.5-1.5mm, covered in simple columnar endothelium. Form the brush border
Epithelial cells in GI functions
Enterocytes. Protection, secretion and absorption
Peptide absorption
Fastest form of protein absorption (most absorbed this way). Proteins absorbed in chains instead of aas. Coupled to Na and H + exchange (enters with H flow). Secondary active transport
Protein across basolateral membrane outline
Moves to interstitial fluid by facilitated diffusion and co-transport. Glutamate and Aspartate provide energy.Transported to liver via hepatic portal vein
