for membranes biochemistry

1. Membranes

2. • Compartmentalization
• Create gradients
• Enzyme activity
• Signal transduction
• Selective passage
Purpose

3. Composition: Lipids
Phospholipids
Sphingolipids
Sterols

4. Composition: Proteins
• Integral/transmembra
ne
• Peripheral – often lipid
anchored

5. Composition:
Carbohydrates
On external surface: glycoproteins & glycolipids

6. Figure 1.5 Early membrane models

7. Fluid Mosaic Model
-Singer & Nicolson (1972) describe integral proteins, lateral
diffusion of lipids and limited transverse diffusion
Figure 1.6 The freeze-fracture
technique reveals “bumps” in the
membrane interior.

8. Figure 1.7 The Fluid Mosaic Model proposed
by Singer and Nicolson

10. Paradigm shift: Lipid Rafts
-Certain domains within the bilayer are not as 'fluid' and are
enriched with proteins (some are anchoring), cholesterol and
sphingolipids
-Signaling domains

12. 3° dimension
• Asymmetry of
membrane
• Interacts with
substances at the
border
• Cytoskeleton