This document discusses the structure and organization of cell membranes. It describes how membrane lipids form a bilayer that behaves like a liquid and allows for membrane protein movement. Membrane proteins have different functions and ways of associating with the lipid bilayer, including spanning it with alpha helices or beta barrels to form channels. The plasma membrane is further structured by a glycocalyx of proteins and the cytoskeleton.

1. Inner organization of the cell
Structure
Barriers
Maintenance of the inner structure of the cell
Function
Transport
Signal transmission
Unity of structure and function
Membrane structure
Membrane transport
Cell compartmentalization and protein sorting
Vesicle transport
Signal transmission

2. Structur & organization of the main
components of biological membranes
Lipid bilayer
Membrane proteins

3. Membrane lipids are amphipatic and
form bilayers in watery milieu

4. Lipid bilayer behaves like a
two dimensional liquid
2mm/s

5. Fluidity depends on the composition of
the lipid bilayer
Fatty acids
saturated
unsaturated
Lipid composition
Cholesterol
Different phospholipids
Glycolipids

6. Cholesterol
A B
Stabilizes lipid bilayer
Prevents transport of small water
soluble molecules
Separates CH-chains to prevent
cristallisation

7. Phospholipids are two-dimensional
solvents for membrane proteins

8. Lipid bilayer is assymetrical

9. Lipid bilayers are not permeable for
solvents and ions

10. Membrane proteins have different
functions
Structure of membrane proteins
Association with lipid-bilayer

11. Membrane proteins can be linked to lipid
bilayer in different ways

12. Most transmembrane proteins span the
lipid bilayer with an αlpha-helix

13. Transmembrane proteins can water-filled
transmembrane channels
Hydrophilic side chains are
directed towards the inner
core of the pore which is
formed by hydrphobic single
chains

14. Maximisation of hydrogen bond
formation through „beta-Barrel“
Example: Porines
16 beta-sheets form
a transmembrane water-
filled channel

15. Plasma membrane proteins
A B
Glycocalix
Protection
Surface recognition
Cell-Cell contacts

16. Cell-cell adhesion in blood

17. Membran proteins can be solved and
purified with detergents

18. The plasma membrane is
enforced by a cytoskeleton

19. Membrane proteins diffuse within the
membrane
Fluorescence recovery
after light bleaching

20. Cells can limit protein and lipid movement
to certain membrane domains
Example: Epithelial cells