PowerLecture: Chapter 5 A Closer Look at Cell Membranes

 CFTR is a protein channel for chloride ions  CFTR is a type of ABC transporter in all prokaryotic and eukaryotic cells Impacts, Issues: One Bad Transporter and Cystic Fibrosis Fig. 5.2, p.75 ATP

 Cystic fibrosis, the most common fatal genetic disorder in the U.S., results from a mutation in CFTR gene Impacts, Issues: One Bad Transporter and Cystic Fibrosis

Section 5.1: Lipid Bilayer  Basic framework  Selectively permeable  Two layers of phospholipids Hydrophilic heads Hydrophilic heads Hydrophobic tails Hydrophobic tails industry/Inex/graphics/lipidbilayer.gif

Studying Membranes Fig. 5.5b, pg. 77 human cell mouse cell fusion into hybrid cell proteins from both in fused membrane Stepped Art

 Every cell membrane has a mixed composition of phospholipids, glycolipids, sterols, and proteins  Most phospholipids and some proteins can drift through membrane Fluid Mosaic Model

Overview of Membrane Proteins Receptor Proteins Recognition Proteins Passive Transporters Active Transporters Fig. 5.6, p.79

Overview of Membrane Proteins Adhesion Proteins Communication Proteins Fig. 5.6, p.78

 Span the lipid bilayer  Passive Ion selective (nerve and muscle cells) Ion selective (nerve and muscle cells) Change shape when they interact with solute Change shape when they interact with solute GluT1 (glucose transporter)GluT1 (glucose transporter) Cotransporter Cotransporter  Active Pump solute (calcium pump, ATPase) Pump solute (calcium pump, ATPase) Transport Proteins

Other Proteins  Receptor -- Bind an extracellular substance that triggers changes in cell activity Antibody Antibody  Recognition – ID tags for species HLAs for tissue defense HLAs for tissue defense  Adhesion – one cell bind to another collagen collagen  Communication – channel between 2 cells Cardiac gap junction Cardiac gap junction

Section 5.3: Concentration Gradient  Different in #/unit volume of a substances between 2 regions  Will move down “down” gradient

Diffusion  Movement of like molecules or ions down a gradient  Molecules move on their own gradient

Factors Affecting Diffusion Rate  Steepness of concentration gradient Steeper gradient, faster diffusion Steeper gradient, faster diffusion  Molecular size Smaller molecules, faster diffusion Smaller molecules, faster diffusion  Temperature Higher temperature, faster diffusion Higher temperature, faster diffusion  Electrical or pressure gradients

Cell Membranes Show Selective Permeability  Some substances enter, but not others  Vital to maintaining homeostasis  Allows NP  Impermeable to ions & lg Polar

Simulation

 Take notes/make sketches of what we did  Note the similarities and differences

Section 5.5: Osmosis  Diffusion of water molecules across a selectively permeable membrane Direction of net flow is determined by water concentration gradient Side with the most solute molecules has the lowest water concentration

Tonicity Tonicity Refers to relative solute concentration of two fluids Hypotonic - having fewer solutes Hypertonic - having more solutes Isotonic - having same amount

2% sucrose solution 1 liter of distilled water 1 liter of 10% sucrose solution 1 liter of 2% sucrose solution Hypotonic Conditions Hypertonic Conditions Isotonic Conditions Fig. 5-13, p.85 Tonicity and Osmosis

What type of solution are these cells in ? A CB HypertonicIsotonicHypotonic

Pressure and Osmosis  Hydrostatic pressure Pressure exerted by fluid on the walls that contain it Pressure exerted by fluid on the walls that contain it The greater the solute concentration of the fluid, the greater the hydrostatic pressure The greater the solute concentration of the fluid, the greater the hydrostatic pressure  Osmotic pressure Amount of pressure necessary to prevent further increase of a solution’s volume Amount of pressure necessary to prevent further increase of a solution’s volume

How Organisms Deal with Osmotic Pressure A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.

How organisms deal with Osmotic Pressure Salt water fish pump salt out of their specialized gills so they do not dehydrate. Salt water fish pump salt out of their specialized gills so they do not dehydrate. Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water. Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.  Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure.

Increase in Fluid Volume hypotonic solution membrane permeable to water but not to solutes hypertonic solution fluid volume rises in second compartment second compartment first compartment Fig. 5.14, p.85

Section 5.4: Passive Transport  Flow of solutes through the interior of passive transport proteins down their concentration gradients  Passive transport proteins allow solutes to move both ways  Does not require any energy input

Passive Transport Stepped Art glucose transporter solute (glucose)‏ high low Fig. 5.10, p.80

Facilitated Diffusion  Help move specific solutes down the gradient  Can be gated

Simulation

 Make notes/sketches of these two processes

Active Transport  Net diffusion of solute is against concentration gradient  Transport protein must be activated  ATP gives up phosphate to activate protein  Binding of ATP changes protein shape and affinity for solute

Active  Help specific solutes diffuse against the gradient

Fig. 5-11, p.83 Active Transport ATP ADP PiPi higher calcium concentration Stepped Art

Active Transport  ATP gives up phosphate to activate protein  Binding of ATP changes protein shape and affinity for solute

Types of Cellular Transport  Passive Transport cell doesn’t use energy 1. Diffusion 2. Facilitated Diffusion 3. Osmosis  Active Transport cell does use energy 1. Protein Pumps 2. Endocytosis 3. Exocytosis high low This is gonna be hard work!! high low Weee e!!! Animations of Active Transport & Passive TransportAnimations

Other types Fig. 5-9, p.81 Endocytosis (vesicles in)‏ Exocytosis (vesicles out)‏

 Take notes/sketches on these two processes.  What parts of endocytosis and exocytosis were not represented?

Section 5.6: Endocytosis and Exocytosis  Exocytosis: A cytoplasmic vesicle fuses with the plasma membrane and contents are released outside the cell

Endocytosis  A small patch of plasma membrane sinks inward and seals back on itself, forming a vesicle inside the cytoplasm – membrane receptors often mediate this process

Fig 5.17, p.87 Macrophage engulfing Leishmania mexicana parasitemacrophage

endocytosis exocytosis coated pit a b d c e f Fig. 5-15, p Traffic to and From the Cell Endocytosis and Exocytosis

endoplasmic reticulum Golgi body vesicle membrane fuses with plasma membrane How Proteins Get to the Surface Fig. 5.18, pg. 87

Endocytosis of cholesterol plasma membranecholesterol