Download Fig. 4.3 - glenbrook s hs

Membranes of the Cell
• Plasma membrane – cell’s outer
membrane
• Endomembranes – smooth and rough
endoplasmic reticulum, golgi, vacuole and
lysosome
• Membraneous envelopes – nucleus,
cholorplast and mitochondria
Membrane Features
• Semi-permeable (selectively permeable) –
allows some substances to pass through, but
blocks the passgae of other substances
• Membranes enclose and maintain the specific
chemical environment
• Every membrane carries out its specific functions
Membrane
Structure
• Two layer membrane called
phospholipid bilayer
– composed of protein and lipids
– Lipids are called phospholipids
– Contain 2 fatty acids instead of 3
• Fatty acids are hydrophobic
– Water fearing
– Avoid water
– Contain a phosphate group in
place of 3rd fatty acid
• Phosphate group is charged making
this hydrophilic
– Water loving
– Mixes with water
•
Specific proteins are
inserted into the
phospholipid bilayer to…
a.
b.
c.
d.
Attach to cytoskeleton
Cell signaling
Enzymatic activity
Transport

Passive and Active
e. Intercellular joining
f. Cell-cell recognition
Membranes
and Proteins
Fig. 4.23
Flexibility
• Membranes are not rigid
• Proteins move freely in the plane of the
membrane
• Called the Fluid Mosaic model
Fluid = molecular wanderings
Mosaic = diversity of protein