Transcript Plasma Membrane: Structure and Function

Plasma Membrane:
Structure and Function
Bellwork

Last unit you learned about the macromolecule
phospholipid. Phospholipids are amphipathic.
Write down what that means.
Objectives
 Describe
the function of the plasma
membrane
 Distinguish between peripheral, integral,
and transmembrane proteins
 Explain the structure of the plasma
membrane based on the Fluid Mosaic
Model
 Explain the role carbohydrates play in cell
to cell recognition
Key Terminology
 Amphipathic
 Peripheral
protein
 Integral protein
 Transmembrane protein
 Fluid Mosaic Model
 Glycoprotein
 Glycolipid
Function
 Acts
as a barrier separating the internal
environment of the cell from the external
environment
 Selectively permeable

controlling what moves in and out of the cell
 All
cells have outer membrane, the plasma
membrane
Unique Structure

Lipid bilayer




composed of phospholipids
polar (hydrophillic) heads
facing the internal and external
aqueous environment
nonpolar (hydrophobic) tails
facing inward towards each other
Phospholipids


amphipathic
have a polar and nonpolar region
of the molecule
External
Internal
Think-Pair-Share
If you compare the cell to a
city, what object in the
city would be analogous
to the cell membrane?
Explain your reasoning.
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Proteins in the Phospholipid Bilayer

Integral Proteins


Peripheral Proteins


embedded in the membrane into the hydrophobic
core
attached to the surface
of the membrane, often to integral proteins
Transmembrane Proteins

go completely across the membrane with ends
sticking out of interior and exterior
Proteins associated with the
Plasma Membrane
Fluid Mosaic Model
 1972,
J. Singer and
G. Nicholson

proposed the fluid
mosaic model
 Phospholipid


bilayer
is envisioned as fluid
with a mosaic of
embedded proteins
floating in the bilayer
Membrane fluidity
Membrane lipids and proteins move
laterally within the membrane
 Lipids move quicker than proteins

Think-Pair-Share
Speculate why lipids do not
move across the
membrane?
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Function of Plasma membrane
Proteins
 Transport-
move ions and polar molecules
across the hydrophobic barrier
 Enzymatic activity-catalyze chemical
reactions
 Receptors- bind chemical signals like
hormones
Membrane Proteins
Think-Pair-Share
In the grocery store, different
items have a bar code.
What is the purpose of that
bar code?
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Cell to Cell Recognition
 Like
bar codes, the cell membrane has a
way to identify different cell types by
surface molecules
 The key molecule is most often
carbohydrates


Usually branched
Attached to either proteins (glycoproteins) or
lipids (glycolipids)
Cell to Cell Recognition
Snapshot
Write a
snapshot in 25
words or less
of what you
learned today
PROPERTY OF PIMA COUNTY JTED, 2010
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