Membranes: Keeping things where they belong

2. Membranes: Keeping things where they belong • Separate functional and anatomic fluid compartments in the body. • Regulate the transport of materials between compartments

4. Connections between plasma membranes • Extracellular matrix: primarily secreted by fibroblasts. • Collagen: forms cable-like fibers that provide tensile strength; especially important in skin and blood vessels. *Scurvy: in vitamin C deficiency these fibers are not properly formed. • Elastin: rubber-like protein where elasticity (ability to return to pre-stress orientation) is important; especially important in arteries and lungs. • Fibronectin: promotes cell-cell adhesion and can hold cells in position.

5. Adjacent intestinal epithelial cells

7. Tight Junctions Intracellular Extracellular Transmembrane Proteins

8. Tight junctions: zona occludens Impermeable (usually) connectio ns between cells. Cell membranes are attached to each other by strands of junctional proteins. Extracellular matrix Connections between plasma membranes

10. Extracellular Intracellular keratin filaments Intracellular Spot Desmosome Thickened “plaque” area Intercellular filaments (commonly glycoproteins)

11. Connections between plasma membranes • Spot desmosomes: macula adherens (~20 nm) • anchor cells together with some space to accommodate movement/stretching. • Cytoplasmic plaque • Intracellular intermediate filaments through cells connecting various plaques • Intercellular glycoprotiens connect the cells • Extracellular matrix • Tight junctions: zona occludens

12. Extracellular Intracellular Passage of ions And small molecules 1.5 nm Large molecules blocked Gap Junctions Connexons

13. Connections between plasma membranes • Gap Junctions: no fancy latin name; 2-4 nm • Communication between cells through connexons • Permit passage of small ions and particles between cell's cytoplasm • Extracellular matrix • Tight junctions: Tight junctions: zona occludens • Spot desmosomes: macula adherens

14. Membrane Transport • Passive: movement of material without the expenditure of energy. • Simple Diffusion • particles in random motion display net movement relative to two conditions • Chemical gradient: material moves "down" it's concentration gradient.

19. * Osmosis:the movement of water "down" it's concentration gradient. *Osmotic pressure:a "negative" effective pressure that acts to "pull" water Membrane Transport • Passive: movement of material without the expenditure of energy. • Simple Diffusion • particles in random motion display net movement relative to two conditions • Chemical gradient: material moves "down" it's concentration gradient.

26. Semi-permeable

27. X mmHg X mmHg

29. Passive: movement of material without the expenditure of energy. Simple Diffusion particles in random motion display net movement relative to two driving force conditions Chemical gradient: material moves "down" it's concentration gradient. Ionic charge: electrical attaction/repulsion Other factors influencing volume-rate diffusion Permeability of the membrane to the substance Lipid-soluble-passes through Water-soluble - generally require selective channels or pores Molecular weight of the substance Surface area Distance (thickness of the membrane) Facilitated (carrier-mediated) diffusion - the diffusion of the material occurs via specialized protein "carriers" Membrane Transport

31. Passive: movement of material without the expenditure of energy. Simple diffusion Facilitated (carrier-mediated) diffusion - the diffusion of the material occurs via specialized protein "carriers" particles in random motion display net movement relative to their electrochemical gradient Display unique characteristics Specificity: only one molecule (or class of molecules) transported Saturation: The rate of transport of molecules is limited to the number of carriers. There are only so many lifeboats on the Titanic Competition: When the carrier can transport multiple forms of a molecule (or drugs that closely resemble the molecule), the multiple forms compete for the limited number of carriers. If a ferry has 100 seats, and 70 are occupied by women, ony 30 men are getting across. Membrane Transport

32. Passive: movement of material without the expenditure of energy. Simple diffusion Facilitated (carrier-mediated) diffusion Active Transport: requiring the expenditure of energy Primary: Energy used directly in transport of the molecule(s) Membrane Transport

34. Passive: movement of material without the expenditure of energy. Simple diffusion Facilitated (carrier-mediated) diffusion Active Transport: requiring the expenditure of energy Primary: Energy used directly in transport of the molecule(s) Typical series of events ATP is used to phosphorylate the carrier carrier becomes exposed to the side with low concentration of the molecule to be transported Increased affinity for the transported molecule Binding of the molecule usually causes conformational (structrural) change Molecule is exposed to high concentration side Carrier is dephosphorylated Affinity for the molecule decreases, and the molecule is released Simple design: one molecule (or class), one direction Complex designs: multiple molecules; mutiple directions Membrane Transport

36. Passive: movement of material without the expenditure of energy. Simple diffusion Facilitated (carrier-mediated) diffusion Active Transport: requiring the expenditure of energy Primary: Energy used directly in transport of the molecule(s) Typical series of events ATP is used to phosphorylate the carrier carrier becomes exposed to the side with low concentration of the molecule to be transported Increased affinity for the transported molecule Binding of the molecule usually causes conformational (structrural) change Molecule is exposed to high concentration side Carrier is dephosphorylated Affinity for the molecule decreases, and the molecule is released Simple design: one molecule (or class), one direction Complex designs: multiple molecules; mutiple directions Counter-transport: multiple molecules, opposite direction (3Na+/2K+) Co-transport: multiple molecules, same direction (not common) Secondary:Potential energy of another molecule used (commonly Na+) Membrane Transport

38. Passive: movement of material without the expenditure of energy. Simple diffusion Facilitated (carrier-mediated) diffusion Active Transport: requiring the expenditure of energy Primary: Energy used directly in transport of the molecule(s) Secondary: Potential energy of another molecule used (commonly Na+) Counter-transport: multiple molecules, opposite direction (Na+/H+) Co-transport: multiple molecules, same direction (Na+/Glucose) Vesicular Clathrin "coated pit" pathway Endocytosis Exocytosis Potocytosis- the caveolae pathway Specialized caveolin-rich "pit" in membranes with cholesterol-stabilized constituents Sometimes maintains "tether" connection to the membrane Involved in many receptor-mediated communication processes Membrane Transport

40. Membrane Potential

41. An electrical potential caused by unbalanced distribution (in/out) of cations and anions. All cells Can primarily be attriubuted to Na/K exchange pump: pumps more cations out than anions in. Differences in permeability to Na and K: cell is much more permeable to K than to Na; the concentration gradient (K our) is balanced by the attraction of anions inside. Membrane impermeable anionic proteins Membrane Potential

43. An electrical potential caused by unbalanced distribution (in/out) of cations and anions. All cells Can primarily be attriubuted to Na/K exchange pump: pumps more cations out than anions in. Differences in permeability to Na and K: cell is much more permeable to K than to Na; the concentration gradient (K our) is balanced by the attraction of anions inside. Membrane impermeable anionic proteins Uses of the membrane potential: Communication via electrical transmission - primarily nerve and muscle Secondary energy source for transport Membrane Potential

44. Cellular Communicaton

45. Autocrine Endocrine

46. Neural

47. Gated Channels- receptor activation "opens" channels for ions to move Electrical potential transmission Ions controlling secretion (eg: Ca) Second-messenger systems G-protein coupled Communications Ligand-receptor mediation

48. GTP E1 E2 γ β α GDP

50. γ γ β β GTP E1 E2 α α GDP