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UCONN - PNB 2264 - PNB 2246 - Class Notes

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UCONN - PNB 2264 - PNB 2246 - Class Notes

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background image Week 3 – Cell Membrane Dynamics Plasma Membrane -“the fluid mosaic model” – molecules can rotate and move laterally but  not transversely(one bilayer to another) Phospholipids are Amphipathic -hydrophobic tails (non-polar) -hydrophilic heads (polar) -Mycell—lipid bilayer forms to get fatty acid tails away from water -Cell membrane does not provide structural support but creates a barrier  Plasma Membrane Proteins  -peripheral proteins- attach to either inner or outer face of membrane  -integral proteins – protrude partly or all the way across membrane, include channel proteins and carrier proteins Transport -paracellular- between cells  -transcellular – through cells The cells that make up lymphatic vessels (which transport fat and large bulky molecules) display 
fewer physical connections between themselves than blood vessels(transcellular). This means that 
lymphatic vessels favor which type of transport?
Paracellular Membranes are  Selectively Permeable -passive transport- does not require energy from the cell, materials move  down the concentration gradient” simple diffusion (net flux goes down concentration gradient) Osmosis (Tonicity: hypertonic -more solutes vs hypotonic- less  solutes) (osmotic force: created by diffusion of water) (hydrostatic force: pressure 
required to block osmosis)
Facilitated diffusion (diffusion through protein not membrane) Bulk filtration- movement of molecules and/or water in same  direction  -active transport-  requires energy molecules are moved “up the  concentration gradient
background image Diffusion -molecular (Brownian motion)---random/erratic  --diffusion is not linear  -happens quickly over short distance and slow over long distances -Diffusion flux of solute is directly related to concentration gradient -Diffusion is proportional to concentration gradient, surface area, lipid  solubility  -Inversely proportional to membrane thickness and molecule size Need circulatory system bc diffusion is super slow over long distances Permeability  -Freely permeable- solutes and solvents can cross membrane, volume  doesn’t change -selectively permeable- solutes can’t move, volume changes Anatomy reflects Physiology -structures that must maximize diffusional flux tend to show expanded  surface area and attenuated linear dimensions (ex. lungs) Channel Mediated:  Ion Channels -selective -passive transport  -are not always open  Mechanically gated sensitive to pressure and stretching  Voltage gated sensitive to change in charge “Channelopathies” -diseases and disorders that are the result of ion channel dysfunction  Fugu puffer fish- tatroto toxin -ion channel blocker- voltage gated sodium channel Glucose facilitated diffusion – glycolysis/citric acid cycle – ATP(signal) - blocks signal 
ligand gated K channel – membrane charge change– voltage gated ca channel 
allows ca in cell- exocytosis insulin 

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School: University of Connecticut
Department: Physiology
Course: Human Physiology and Anatomy
Professor: Kristen Kimball
Term: Fall 2018
Name: PNB 2246
Description: Notes cover all power-point information as well as what was covered in class.
Uploaded: 09/16/2018
4 Pages 78 Views 62 Unlocks
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