1. 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?

2. A Fluid Mosaic model of biological membranes
This and all other images in this vidoe are from Wikimedia Commons unless otherwise noted

3. All Cells Have Phospholipid Bilayer Membranes
Phospholipids with fatty acid esters

4. 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)

5. Sterols and sphingolipids are eukaryotic innovations
Cholesterol

6. Hopanes are bacterial equivalents of sterols

7. Variation in membrane fatty acids in eukaryotes

8. Cis- and trans-unsaturated fatty acids

9. Membranes and Transport Part B
Membrane Proteins Transport

10. Membrane Proteins rhodopsin Integral membrane protein transducin
G-protein
Peripheral membrane protein

11. Functions of membrane proteins
Cell signaling
Transport across membranes
Energy metabolism
Cell adhesion
Cell movement
Cell structure

12. Diffusion and Osmosis
Diffusion of solute molecules through pores in a membrane
Time
Osmosis of water molecules across a semipermeable membrane

13. 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

14. Aquaporin molecular animation

15. Transport across cell membranes
Simple diffusion Facilitated diffusion Active transport

16. Facilitated diffusion and active transport show saturation kinetics
Rate of transport into the cell
Answer: C
The X-axis is the difference in concentration, expressed as the concentration outside the cell minus the concentration inside the cell. A negative value means that the concentration is higher inside the cell than outside the cell.
[solute]out – [solute]in