Download - 3-2 Part A: Membranes and transport
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Georgia Tech School of Biology
Georgia TechBiol 1510
3-2 Part A: Membranes and transport• What are the structures and lipid compositions
of cell membranes in Bacteria, Archaea and Eukarya?
• How do changes in membrane components affect membrane properties and function?
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Georgia Tech School of Biology
Georgia TechBiol 1510
A Fluid Mosaic model of biological membranes
This and all other images in this vidoe are from Wikimedia Commons unless otherwise noted
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Georgia Tech School of Biology
Georgia TechBiol 1510
All Cells Have Phospholipid Bilayer Membranes
Phospholipids with fatty acid esters
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Georgia Tech School of Biology
Georgia TechBiol 1510
Archaea have different membrane phospholipids from Eubacteria and Eukarya
• Branched isoprenoid chains (1) vs fatty acids (5)
• Ether linkage (2) vs ester linkage (6)
• L-glycerol (3) vs D-glycerol (7)
• 2-sided monolayer (10) vs bilayer (9)
http://en.wikipedia.org/wiki/Archaea
http://www.ucmp.berkeley.edu/archaea/archaeamm.html
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Georgia Tech School of Biology
Georgia TechBiol 1510
Sterols and sphingolipids are eukaryotic innovations
Cholesterol
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Georgia Tech School of Biology
Georgia TechBiol 1510
Hopanes are bacterial equivalents of sterols
http://www-eaps.mit.edu/geobiology/biomarkers/hopanoids.html
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Georgia Tech School of Biology
Georgia TechBiol 1510
Variation in membrane fatty acids in eukaryotes
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Georgia Tech School of Biology
Georgia TechBiol 1510
Cis- and trans-unsaturated fatty acids
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Georgia Tech School of Biology
Georgia TechBiol 1510
Membranes and Transport Part BMembrane ProteinsTransport
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Georgia Tech School of Biology
Georgia TechBiol 1510
Membrane Proteinsrhodopsin
transducinG-protein
Integral membrane protein
Peripheral membrane protein
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Georgia Tech School of Biology
Georgia TechBiol 1510
Functions of membrane proteins
• Cell signaling• Transport across membranes• Energy metabolism• Cell adhesion• Cell movement• Cell structure
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Georgia Tech School of Biology
Georgia TechBiol 1510
Diffusion and Osmosis
Time
Osmosis of water molecules across a semipermeable membrane
Diffusion of solute molecules through pores in a membrane
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Georgia Tech School of Biology
Georgia TechBiol 1510
How does water cross the membrane?Aquaporins
– Water channel proteins– Ubiquitous – bacteria, archaea,
eukaryotes– Tetramers – one channel per
monomer– Some are “gated”; open or close
in response to cellular signals– Central channel may allow
passage of other molecules, ions
http://www.ks.uiuc.edu/Research/aquaporins/
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Georgia Tech School of Biology
Georgia TechBiol 1510
Aquaporin molecular animation
http://www.ks.uiuc.edu/Research/aquaporins/
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Georgia Tech School of Biology
Georgia TechBiol 1510
Transport across cell membranes
Simple diffusion
Facilitated diffusion
Active transport
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Georgia Tech School of Biology
Georgia TechBiol 1510
Facilitated diffusion and active transport show saturation kinetics
[solute]out – [solute]in0