Digestion and Absorption

Digestion and Absorption

1. Food broken down into smaller molecules

   • Too big to cross cell membranes
     • Cant be absorbed
     • Broken down
       • Easily absorbed

2. Hydrolysis

   • polymers to monomers
   • Carbohydrates
     • Disaccharides
       • Monosaccharides
   • Fats
     • Fatty Acids
       • Monoglycerides
   • Proteins
     • Amino Acids

3. Enzymes needed

   • Carbohydrates
     • Amylase
       • Starch to Maltose
         • Glycosidic bonds
       • Produced
         • Salivary glands
         • Pancreas
       • Secreted
         • Small Intestine
     • Membrane-Bound Disaccharides
       • Cell membranes of epithelial cells
         • Ileum
       • Disaccharides to Monosaccharides
         • Can now be transported across cell membrans of the Ileum by transported proteins
   • Lipids
     • Lipase
       • Monoglycerides
         • Ester Bonds
       • Fatty Acids
         • Stick together with Bile to make Micelles
       • Produced
         • Pancreas
       • Secreted
         • Small Intestine
     • Bile Salts
       • Produced
         • Liver
       • Emulsify Lipids
         • Small droplets
           • Large surface area
   • Proteins
     • Endopeptidases
       • Within
       • Increase the surface area for
       • Trypsin and Chymotrypsin
         • Synthesised in the Pancreas
           • Secreted in the small intestine
         • Pepsin
           • Released in the stomach by the stomach lining
     • Exopeptidases
       • At the end
         • Remove single amino acids
     • Helped by the enzyme of Membrane-Bound Dipeptidases
       • Work specifically on Dipeptides break up two amino acids
       • Small intestine in the cell-surface membrane
     • Protease

4. Absorbed across the ileum epithelium into the bloodstream

   • Monosaccharides
     • Glucose and Galactose
       • Absorbed by active transport along with sodium ions
         • Co-transporter proteins
     • Fructose
       • Facilitated diffusion
   • Monoglycerides and Fatty Acids
     • Micelles
       • Move them towards the epithelium
         • Absorbed because the micelles constantly break up and reform
     • lipid-soluble so can diffuse directly across
   • Amino acids
     • Sodium diffuses back into cells through sodium-dependent transporter proteins carrying amino acids with them