BIOL2171 Lecture Notes - Lecture 16: Transport Protein, Chymotrypsin, Trypsin
Amino Acid Transport
• Proteins make up 30% of our nutrition
o 10-15% of total energy production
• Cant completely oxidised into carbon dioxide and water, have an amino group
• In stomach and small intestine proteins are digested by a variety of proteases
o Trypsin
o Chymotrypsin
o Pepsin
o Carboxypeptidases
o Aminopeptidases
o And more
• Resulting amino acids are absorbed by epithelial cells lining the intestine
• Absorptive surface of the intestine is enlarged by villi
o Protrude into the lumen a
o Are the principle sites of nutrient absorption
• Transport proteins in membranes of epithelial cells mediate the uptake of nutrients
Protease Action
• Intestinal proteases use several mechanisms to hydrolyse proteins and peptides
• Meat: high protein - main source of protein
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• Case study: trypsin (outlines in practical course and lectures)
• Catalytic trade
o Has three key residues in the active centre (in all protease)
• Serine: most important catalytic residue
• Histidine
• Aspartate
• Called the triade
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• All look far apart but when protein folds they are close together
• Enzymes in stomach fully denature protein (very low pH)
• Chymotrypsin: must have hydrophobic side chain
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• Eddie H:
o Case study
o Had Hartnup disorder
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Document Summary
Amino acid transport: proteins make up 30% of our nutrition, 10-15% of total energy production, cant completely oxidised into carbon dioxide and water, have an amino group. Intermediate binds stringer to the active centre than the substrate. Subsequently, water attacks the ester bond releasing the amino-terminal peptide: reaction passes through a tetrahedral intermediate again, which is tightly bound, mechanism: Filtration of blood: liver and kidney: after absorption into intestine, amino acids are delivered of the liver by the portal vein. Liver has important function as gate-keeper in the body: toxic substances will be removed, most nutrient metabolised here, portal vein branches out allowing nutrients to be captured by hepatocytes and processed further. Transport proteins: without transport proteins, biological membranes are essentially impermeable to hydrophilic substances, to allow passage of amino acids, transport proteins are essential, transport proteins are similar to enzymes.