Digestion and Absorption Johnson Chap Jack L. Leonard 2004

Johnson Chap Epithelial Cell Structure

Johnson Chap Cell membrane Glycocalyx Transport carrier ExtrinsicenzymeIntrinsicenzymeMicrovillus

Johnson Chap ,4 link 1,6 link  -limit dextrins  amylase maltotriose maltose amylopectin Initial breakdown of starch

Johnson Chap Amylose

Amylopectin

Cellulose

Sucrose

Lactose

Maltose

glucose galactose fructose sucrose lactose  -limit dextrins (G5-G9) Malto-oligosaccharides Starchglycogen  amylase glucose Glucosetransporter Na + G GaGF G-G-G-G G-G-G 40% G 2 25% G 3 5% G 4 -G 9 Lactase Glucosecarrier Fructosecarrier Sucrase  -dextrinase Glucosecarrier Glucoamylase Brush Border CHO enzymes

Johnson Chap Enzyme Primary Action Endopeptidases Hydrolyze(s) interior peptide bonds containing Pepsin Pepsin Aromatic amino acids Trypsin Trypsin Basic amino acids Chymotrypsin Chymotrypsin Aromatic amino acids—leu, met, gln—C-terminal residue Elastase Elastase Neutral aliphatic amino acids Exopeptidases Hydrolyze(s) external peptide bonds containing Carboxypeptidase A Carboxypeptidase A Aromatic and neutral amino acids—aliphatic AA at C-terminus Carboxypeptidase B Carboxypeptidase B Aromatic and neutral amino acids—basic AA at C-terminus Principal luminal proteases

Johnson Chap Principal luminal absorption

Johnson Chap Intact Protein Absorption

Johnson Chap Principal luminal absorption

Johnson Chap Digestion of Fat

Johnson Chap Absorption of Sugars

Johnson Chap Carrier AA transported Neutral (  -amino- monocarboxylic) Aromatic (Phe, Tyr, Trp) Aliphatic (Gly, Ala, Val, Leu, Ile, Ser His, Met, Asn, Gln, Cys, Pro, OH-Pro Basic (cationic) Lys, Arg, Orn, Cys Acidic (anionic) Glu, Asp, SeC Imino Pro, OH-Pro, GABA, Tau, Gly, other AA with amino groups in  or  positions Amino Acid Carrier Systems

Johnson Chap Absorption of Fluid and Ions Cl K+K+K+K+ ATP Na + Lumen Serosal surface glucose Na + K+K+K+K+ ATP H+H+H+H+ + HCO 3 - H+H+H+H+ H 2 CO 3 H2OH2OH2OH2O CO 2 + CO 2 metabolism + HCO 3 - H+H+H+H+ H 2 CO 3 H2OH2OH2OH2O CO 2 + HCO 3 - Cl -

Johnson Chap Na ~ ~ ~ H K Na K K [K~155 mM] 32 mV Na mV mV 47 mV -15 mV + - Serosa Mucosa