Chapter 4 Movement of Molecules Across Cell Membranes Trans-Membrane Traffic Diffusion:solute moves down its concentration gradient: ·simple diffusion: small(e.g.,oxygen,carbon dioxide) lipid soluble (e.g.,steroids) facilitated diffusion: requires transporter (e.g.,glucose)
Diffusion: solute moves down its concentration gradient: • simple diffusion: small (e.g., oxygen, carbon dioxide) lipid soluble (e.g., steroids) • facilitated diffusion: requires transporter (e.g., glucose) Chapter 4 Movement of Molecules Across Cell Membranes = Trans-Membrane Traffic
Chapter 4 Movement of Molecules Across Cell Membranes Trans-Membrane Traffic(cont.) Active transport:solute moves against its concentration gradient: primary active transport: ATP directly consumed (e.g.,Na+K+ATPase) secondary active transport: energy of ion gradient(usually Na+)used to move second solute (e.g.,nutrient absorption in gut) Exo-and endo-cytosis: large scale movements of molecules
Active transport: solute moves against its concentration gradient: • primary active transport: ATP directly consumed (e.g., Na+ K+ATPase) • secondary active transport: energy of ion gradient (usually Na+) used to move second solute (e.g., nutrient absorption in gut) Exo- and endo- cytosis: large scale movements of molecules Chapter 4 Movement of Molecules Across Cell Membranes = Trans-Membrane Traffic (cont.)
Figure 4-1 START:Initially higher concentration of molecules randomly move toward lower concentration. Over time, solute molecules placed in a solvent will evenly distribute themselves. Diffusional 6 equilibrium d is the result (Part b). d 00
Over time, solute molecules placed in a solvent will evenly distribute themselves. START: Initially higher concentration of molecules randomly move toward lower concentration. Diffusional equilibrium is the result (Part b). Figure 4-1
Figure 4-2 At tim s into side 1 TimeA Time B Time C 20 Compartment 1 10 -Compartment 2 Time
At time B, some glucose has crossed into side Figure 4-2 2 as some cross into side 1
Compartment 1 Compartment 2 High solut Low solu ute concentration One-way flux e-way flux Net flux Note:the partition between the two compartments is a membrane that allows this solute to move through it. Net flux accounts for solute Figure 4-3 movements in both directions
Note: the partition between the two compartments is a membrane that allows this solute to move through it. Figure 4-3 Net flux accounts for solute movements in both directions
ubun 3 cartoon models of integral membrane proteins that function as ion channels;the regulated opening and closing of these channels is the basis of how neurons function. Figure 4-5
Figure 4-5 3 cartoon models of integral membrane proteins that function as ion channels; the regulated opening and closing of these channels is the basis of how neurons function
A thin shell of positive (outside)and negative(inside) charge provides the electrical gradient that drives ion movement across the membranes of excitable cells. CopyrightTheM-ll Companies In Extracellular fluid Intracellular fluid ⊕ Figure 4-6
Figure 4-6 A thin shell of positive (outside) and negative (inside) charge provides the electrical gradient that drives ion movement across the membranes of excitable cells
Copyright The McGraw-Hi n requlred for reproduction or display Figure 4-7 CopyrightThe McGraw-Hill Companies,Ine.Permission required for reproduction or display. Intracellular fluid Channel proteins Lipid bilayer Open ion channel Closed ion channel Extracellular fluid The opening and closing of ion channels results from conformational changes in integral proteins. Discovering the factors that cause these changes is key to understanding excitable cells
The opening and closing of ion channels results from conformational changes in integral proteins. Discovering the factors that cause these changes is key to understanding excitable cells. Figure 4-7
Copyright The McGraw-Hill Comp A cartoon model of carrier-mediated transport. Copyright The McGraw-Hill Companies,Inc.Permission required for reproduction or display. Intracellular fluid Trans rter Binding site protei o Transported solute Extracellular fluid The solute acts as a ..and then a subsequent ligand that binds to shape change in the the transporter protein releases the protein.... solute on the other side Figure 4-8 of the membrane
The solute acts as a ligand that binds to the transporter protein…. Figure 4-8 A cartoon model of carrier-mediated transport. … and then a subsequent shape change in the protein releases the solute on the other side of the membrane
Copyright The McGraw-Hill Co for reproduction or display Figure 4-9 In simple diffusion, flux rate is limited only by the concentration gradient. Diffusion In carrier- mediated transport, Maximal flu> the number of available carriers places an Mediated transport upper limit on the flux rate. Extracellular solute concentration
In simple diffusion, flux rate is limited only by the concentration gradient. In carriermediated transport, the number of available carriers places an upper limit on the flux rate. Figure 4-9