IMG_4308

Topic 03 Section C Chapter 8 of Comparative Animal Nutrition and Metabolism Animal Nutrition: Absorption in General O How are nutrients absorbed from the gastrointestinal tract? » Passage of nutrients across cell membranes occurs by: > passive transport: v down _ aconcentration gradient = High to low concentration v diffusion (no transport channel) : ¥ facilitated diffusion __(via transport channel)3 > active transport: pa = < viagainst __ a concentration gradient ‘1‘ R = Low to high concentration Y4 v'Needs a transport __channel v'Needs to be linked to _ eneragy » Endocytosis/exocytosis v endocytosis__ - engulfs nutrients orions & v exocytosis _ - fusion of secretory vesicles with membrane - 1.\:m|med diffusior ANSC 422/522 Animal Nutrition: Absorption in General O How is energy linked to active transport? > Na‘K* ATPase _ (Sodium Pump): v'Found on _basolateral __ membrane of absorptive cells in intestinal epithelium v'Links _eneray __ to absorptive/secretive processes = Major energy-requiring action in the body » Action of Na*K* ATPase: Outiide v'Transports 3 Na* outand 2 K- into cell - Na & K are electrolytes = Requires energy (ATP — ADP + Pi) v'Creates electro-chemical gradient o = negative charge inside cell % " Jow Na* inside cell 2 v Electro-chemical gradient used to drive other transporters 3Na* 2K +P; Na+ 2K+