transported molecule co-transported ion lipid bilay UNIPORT SYMPORT ANTIPORT coupled transport Figure 11-8 Three types of carrier-mediated transport. The schematic diagram shows carrier proteins functioning as uniport symports, and antiports
Figure 11-8 Three types of carrier-mediated transport. The schematic diagram shows carrier proteins functioning as uniports, symports, and antiports
Carrier proteins bind one or more solute molecules on one side of the membrane and then undergo a conformational change that transfer the solute to the other side of the membrane solute lipid pong ing bilayer OUTSIDE ④④ electrochemical gradient INSIDE carrier protein mediating facilitated diffusion
❖Carrier proteins bind one or more solute molecules on one side of the membrane and then undergo a conformational change that transfer the solute to the other side of the membrane
Facilitate diffusion: Protein-mediated movement, movement down the gradient OUTSIDE OF CELL Transport protein ① shifts to alternative Glucose binds conformation Glucose is to binding site released to the open to outside inside and protein returns to its original Glucose conformation INSIDE OF CELL Glucose Glucose transporter (GT1) The carrier protein, the Glucose transporter(GluT1) in the erythrocyte PM, alter conformation to facilitate the transport of glucose
The carrier protein, the Glucose transporter (GluT1 ) in the erythrocyte PM, alter conformation to facilitate the transport of glucose. ❖Facilitate diffusion: Protein-mediated movement, movement down the gradient
Most of the channel proteins are ion channels including three types, with ion channels that they can be opened and closed voltage ligand-gated Higand-gated mechanically gated Extracellular (intracellular gated ligand) ligand CLOSED OPEN CYTOSOL
❖Most of the channel proteins are ion channels, including three types, with ion channels that they can be opened and closed
acetyicholine- binding site lipid channel bilay ore 4 nm CYTOSOL gate Figure 11-36. A model for the structure of the acetylcholine receptor. Five homologous subunits(a, a, b, g, d)combine to form a transmembrane aqueous pore The pore is lined by a ring of five transmembrane a helices, one contributed by each subunit In its closed conformation the pore is thought to be occluded by the hydrophobic side chains of five leucines, one from each a helix, which form a gate near the middle of the lipid bilayer. The negatively charged side chains at either end of the pore ensure that only positively charged ions pass through the channel. Both of the a subunits contain an acetylcholine-binding site; when acetylcholine binds to both sites, the channel undergoes a conformational change that opens the gate possibly by causing the leucines to move outward
Figure 11-36. A model for the structure of the acetylcholine receptor. Five homologous subunits (a, a, b, g, d) combine to form a transmembrane aqueous pore. The pore is lined by a ring of five transmembrane a helices, one contributed by each subunit. In its closed conformation, the pore is thought to be occluded by the hydrophobic side chains of five leucines, one from each a helix, which form a gate near the middle of the lipid bilayer. The negatively charged side chains at either end of the pore ensure that only positively charged ions pass through the channel. Both of the a subunits contain an acetylcholine-binding site; when acetylcholine binds to both sites, the channel undergoes a conformational change that opens the gate, possibly by causing the leucines to move outward