Download Digestion of Biomolecules

Digestion of Biomolecules
Stryer Short course
Chapter 14
Hydrolysis Reactions
• Proteins amino acids
– Proteases, peptidases
• Complex carbohydrates  monosaccharides
– amylase
• Triacylglycerides  fatty acids
– lipase
Zymogens
• Proenzymes—inactive precursors
• Cannot release digestive enzymes everywhere!
• Pepsinogen  pepsin: autocatalysis at low pH
Pancreatic Zymogens
Mechanism
• Protease activates trypsin
• Trypsin activates other zymogens
Stomach
• Highly acidic, denaturing environment
• Pepsin begins work
• Acidic, partially digested food enters intestine
– Activates secretin to neutralize adic
– Activates hormone causing release of pancreatic zymogens and bile salts
Stomach acid
• Prilosec: irreversible inhibitor of proton, potassium pump
Error in carbonic anhydrase
Proteins in the Intestine
• Protein digestion continues with proteases in lumen
• Transporter proteins essential—basis of some genetic diseases
• Amino acids then sent to liver
• Gluten sensitivity
Carbohydrates in the Intestine
• ‐amylase
• Limiting dextrins
• Maltase, sucrose, lactase, glucosidase, dextrinase all work to digest to monosaccharides
Carbohydrate Transporters
Lipid Digestion
• Complicated by insolubility
• Emulsion form in stomach
• Extra steps of degradation/re‐
assembly
• Bile salts
– Cholesterol lowering medications
Pancreatic Lipases
• Zymogens
• Fatty acids and MAG
• Miscelle formation
Transport to Liver
• Fatty acid binding proteins
• Fatty acid transport proteins
• Smooth enoplasmic
reticulum
• chylomycrons