Date:
EQ: What are the structure and function of a cell membrane?
Questions
(Costa’s Levels )
Topic: Plasma membrane (cell membrane)
All cells are surrounded by a cell membrane.
Function
 Boundary – separates internal metabolic events from external environment
 Regulates movement (or transport) of materials into & out of cell = selectively permeable =
Gatekeeper; traffic cop
Composition
 Phospholipids bi-layer
o Polar hydrophilic heads (phosphate groups) forming outer “faces”
- Hydro- means “water”
- Hydrophilic means attracted to water (water loving)
o Non-polar hydrophobic fatty acid tails facing each other in middle
- Hydrophobic means repelling water (water fearing)
o
o

The fatty acid tails orient towards each other creating a hydrophobic environment
within the membrane
The charged phosphate groups facing out into the hydrophilic environment
Proteins are scattered throughout membrane
o Peripheral Proteins: Attach loosely to inner or outer surface of membrane
o Integral Proteins: Extend into membrane or Span across membrane
A-phospholipid bilayer
B-integral protein
C-Glycoprotein
E-glycolipid
F-fatty acid tails
G-phosphate head
H-peripheral protein
I-cholesterol

Summary:
“Fluid Mosaic Model”. Fluid because individual phospholipids and proteins can move around
within the layer, like it’s a liquid. Mosaic- b/c scattered proteins.