Cell Membrane : Structure and Function



Name : __________________________

Date: ________________

Cell Membrane : Structure and Function

 

Cell Membrane Structure:

- Early Theory: After chemically analyzing cell membranes, scientists discovered

that the ________________________________________________________________

______________________________________________. They then proposed that the Proteins were sandwiched between two layers of phospholipid molecules. (as illustrated below)

[pic]

- Problem: Since the phospholipid tails are hydrophobic (hate water) ____________

________________________________________________________________________

________________________________________________________________________

 

"_______________________________________":

- Accepted Theory: There is a double layer of phospholipids but the proteins are scattered through the membrane ( ________________). These embedded proteins float (raft around) among the semi-fluid phospholipids (________________). Many

of these ___________________________ (seen in brown below) _________________

______________________________________________________________________.

[pic]

- Water travels through special protein pores called _______________________

[pic]

The proteins have polar and non-polar regions from the amino acid R-Groups,

which accounts for their placement among the phospholipid bilayer. ___________

_______________________________________________________________________

_______________________________________________________________________

________________________________________________where water flows through.

- Some of the proteins and phospholipids have carbohydrate chains attached to them.

[pic]

- _______________ + ____________________________ = _______________________

- _______________ + ____________________________ = _______________________

- These carbohydrate chains function as cell identification markers. Forming

somewhat of a fingerprint on the outside of the cell. ___________________________

_____________________________________________ (like a foreign cell, cancer cell, or infected cell)

Example: Organ rejection after a transplant. 

Cell Membrane Function:

 

- ______________________ – ___________________________________________

- ______________________ – ___________________________________________

- ______________________ – smaller molecules pass through but not larger ones. Like a Strainer/Sieve.

 

- The cell membrane is described as being __________________________________ (differentially permeable)-- only certain desirable molecules can pass through,

_______________________________________________________. The membrane has mechanisms to allow for the transport of various types of desirable molecules.

 

Example : Protein molecules are too large to fit through the various protein pores, but they can be transported across the membrane with vesicle formation.

[pic]

[pic]

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Phospholipids

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