7.2 PLASMA MEMBRANE
7.2 THE PLASMA MEMBRANE
WHAT YOU WILL LEARN:
-how a cell’s plasma membrane functions
-the roles of proteins, carbohydrates &
cholesterol in the plasma membrane
READING QUESTIONS
1-HIGHLIGHT the items in the figure that enter the
cell thru pm/CIRCLE those that exit the cell
oxygen
water
glucose
READING QUESTIONS
2-EXPLAIN the purpose of phospholipid bilayer?
-allows plasma membrane to survive & function in its
watery environment
READING QUESTIONS
3-IDENTIFY: CIRCLE one phospholipid—LABEL its
head/tail
head
tail
READING QUESTIONS
4-DEFINE the role of transport proteins
-move substances through plasma membrane
5-NAME 3 substances that move among the
phospholipids of the PM
-proteins/carbohydrates/cholesterol
• http://www.dnatube.com/video/360/FluidMosaic-Model
• http://www.susanahalpine.com/anim/Life/me
mb.htm
7.2 THE PLASMA MEMBRANE
REVIEW -homeostasis:
-maintain balance / internal environment
http://www.dnatube.com/video/360/Fluid-Mosaic-Model
FUNCTION of the PLASMA MEMBRANE
selective permeability--CONTROLS substances ENTER / LEAVE (homeostasis)
WHAT WHEN HOW
*cells must keep proper concentration of nutrients / water / expel waste
-some molecules can cross the plasma membrane --(water)
-others must go through channels --(Na, Ca, etc)
This is like a FISH NET--HOW?
T/P/S: analogy for a cell’s selective permeability
FUNCTION of the PLASMA MEMBRANE
FUNCTION of PLASMA MEMBRANE
-boundary separates cell & environment
-allows water, nutrients & oxygen into cell
-allows waste & CO2 out of cell
OUTSIDE CELL
NUTRIENTS
WATER
OXYGEN
CARBON
DIOXIDE
INSIDE CELL
WASTE
STRUCTURE of PLASMA MEMBRANE
polar
head—
hydrophilic
…likes water
non-polar tail—
hydrophobic
…repels water
STRUCTURE of PLASMA MEMBRANE
STRUCTURE of PLASMA MEMBRANE
A- carbohydrate
chain
C- polar
heads
B- transport 
protein
D- non-polar
tails
E-cholesterol 
STRUCTURE of PLASMA MEMBRANE
B- lipids
C- phospholipid
A- transport protein
F- phospholipid bilayer
D- fluid mosaic model
E- selective permeability
FUNCTION of the PLASMA MEMBRANE
DESCRIPTION
1-The process of maintaining balance inside a
cell.
2-A boundary between a cell & its
environment.
3-Feature of plasma membrane that keeps
some substances out.
4-Separates prokaryotic & eukaryotic cells
from the watery environment in which they
exist
5-The quality of a plasma membrane that
allows oxygen & glucose to move in
6-Maintained by the plasma membrane
SELECTIVE
HOMEOSTATSIS PLASMA
PERMEABILITY
MEMBRANE
STRUCTURE of PLASMA MEMBRANE
-polar heads
barrier to water environment in/out of cell
-non-polar tails
prevent substances dissolve in water from passing thru PM
-carbohydrate chain
identify chemical signals from environment
-cholesterol
prevent tails from sticking together, keep membrane fluid
-transport protein
like tunnels--move materials thru plasma membrane
-membrane protein
receptors—on outside, send signals to inside of cell
anchors—on inside, hold membrane to cell’s internal shape
STRUCTURE
of PLASMA MEMBRANE
EXPLAIN/DRAW
1-MEMBRANE PROTEIN
-create tunnels
-PASSIVE
2-TRANSPORT PROTEIN
-create tunnels
-”pump” substances / ACTIVE
STRUCTURE
of PLASMA MEMBRANE
EXPLAIN/DRAW
CHOLESTEROL
-non polar
-keeps PM fluid--prevents fatty acid tails from sticking
-maintains homeostasis in cell
CARBOHYDRATE CHAIN
-help cell identify chemical signals from environment
FLUID MOSAIC MODEL
This “MODEL” for the structure of the membrane is called the:
FLUID MOSAIC MODEL
FLUIDindividual phospholipids / proteins move freely within the layer-- like a
liquid
MOSAIC“pattern” produced by the scattered protein molecules
21
Cell Membranes from Opposing Neurons
(TEM x436,740).
Nerve cell
Cell membrane {
Gap between cells
}
cell membrane
7nm wide
Nerve cell
AS Biology. Foundation. Cell membranes
and Transport
22