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Cell Membrane
Transport
Membrane Structure
Membrane is composed of...
a. -phospholipids arranged in a bilayer
b. -proteins inserted in bilayer for
movement of molecules
c. – carbohydrates for cell to cell
recognition
d. – cholesterols to keep membrane
flexible
We describe cell membranes as a
fluid mosaic model
fluid mosaic model
animation
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Lets look at the 4 major parts
1. phospholipid bilayer
3. interior protein network
2. transmembrane proteins
4. cell surface markers
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Membrane structure is visible using an
electron microscope.
Transmission electron microscopes (TEM)
can show the 2 layers of a membrane.
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Membrane Proteins have many
functions
1. transporters
2. enzymes
3. receptors
4. identity markers
5. cell-to-cell adhesion
6. attachments to cytoskeleton
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Proteins move things by…
I. Passive transport :
1. no energy is required
2. moves substances from high concentration to
low concentration
II. Active transport:
1. requires energy (ATP)
2. moves substances from low concentration to
high concentration
Bulk Transport
Bulk transport is accomplished by
1. endocytosis – movement of substances
into the cell
2. exocytosis – movement of materials out
of the cell
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Bulk Transport (endocytosis)
1. Phagocytosis Non selective
2. Pinocytosis Non selective
3. Receptor mediated Substrate specific
Bulk Transport (exocytosis)
vesicles in the cytoplasm fuse with membrane
and release their contents to the
exterior of the cell
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lets see it all together......
“fluid mosaic model”