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Plasma Membrane
Movement in and out of a cell
Plasma Membrane
A flexible boundary between the cell and
it’s environment
JOB: allow steady supply of nutrients to
come into the cell no matter what the
external conditions are

Too much of any nutrient or other substance
can be harmful
Plasma Membrane (PM)
Process of maintaining balance in a cell’s
environment is homeostasis

Selective permeability allows some
molecules to pass through while keeping
other out
Ex: screen on a window
PM: Structure
Lipids are large
biomolecules
composed of glycerol
and 3 fatty acids


If a phosphate
replaces one of the
fatty acids, a
phospholipid is
formed
PM is made up of a
phospholipid bilayer
(2 layers of
phospholipids back-toback
PM: Structure
2 fatty acid chains are non-polar and
form the tail of the phospholipid
The head contains the phosphate group
and is polar
Continued
Water is a key component of life
Polar head allows PM to interact with
watery environment (H2O is a polar
molecule) (Hydrophyllic) water loving
Non-polar tails avoid water (Hydrophobic)
water fearing
Phospholipid molecules make a sandwich
with tails in, heads out.
PM: Fluid Mosaic Model
PM is not static (it
doesn’t stay still)
Phospholipids move
within the membrane
like water molecules
move with currents in a
lake
Proteins also move
through phospholipids
like boats

Proteins create “mosaic”
or pattern on membrane
surface
PM: Other Components
Cholesterol: helps stabilize phospholipids
by preventing tails from sticking together
Transport proteins: Span entire
membrane

Regulate which molecules enter and leave
cell
Proteins on OUTER surface help cells identify
chemical signals and each other
Proteins on INNER surface help attach PM to cells
internal support structure  flexibility
PM: Other Components
Show me What You Know
The structure most responsible for
maintaining cell homeostasis is the ___.
A. Cytoplasm
B. Mitochondrion
C. Cell Wall
D. Plasma Membrane
Show me What You Know
The structure most responsible for
maintaining cell homeostasis is the ___.
A. Cytoplasm
B. Mitochondrion
C. Cell Wall
D. Plasma Membrane
Show Me What You Know
Movement of particles from an area of
higher concentration to one of lower
concentration is ______________?
Show Me What You Know
Movement of particles from an area of
higher concentration to one of lower
concentration is ______________?
Diffusion
Show Me What You Know
Which of the following structures is the most
complex?
A. Cell
B. Organ System
C. Organ
D. Tissue
Show Me What You Know
Which of the following structures is the most
complex?
A. Cell
B. Organ System
C. Organ
D. Tissue
Activity
Write your summary of notes
On the left hand side of your notebook,
draw and label a phospholipid bilayer.
Use p. 177-178 of your text. Don’t forget
to add color.
Plasma Membrane
Day Two
Cell Transport
2 types of cell transport:

Passive Transport: Movement of particles
across a membrane requiring NO energy
High concentration  Low concentration

Active Transport:
Passive Transport: Osmosis
Osmosis: diffusion of H2O across a
selectively permeable membrane.

Ex. If membrane that only allows water to
pass through, water will diffuse to side where
H2O concentration is lower and will continue
until equal concentration is reached on both
sides
Passive Transport: Osmosis
Isotonic Solution: Concentration is the
same both inside and outside the cell
Hypotonic Solution: concentration is
lower outside than inside the cell
Hypertonic Solution: concentration is
higher outside than inside the cell
Passive Transport: Osmosis
Passive Transport: Diffusion
Diffusion: net movement of particles from
higher concentration to lower.


Results from random movement of particles
running into one another
Very slow process because it relies on
random motion
Continued

3 key factors:
Concentration: Increase in concentration will
increase the rate of diffusion
Temperature: Increase in temperature will increase
rate of diffusion
Pressure: Increase in pressure will increase rate of
diffusion

Dynamic Equilibrium: continuous
movement with no overall concentration
change
Passive Transport: Diffusion
Active Transport
Active Transport: Movement of materials
through a membrane against a
concentration gradient (requires energy)
Active Transport: Carrier Transport
Proteins
Carrier Proteins:



Bind with particle of the
substance to be
transported
Lock and Key!!
With the right fit, chemical
energy allows shape of
carrier protein to change
releasing particle on other
side
Much like the action of a
door
Active Transport: Carrier
Proteins
Active Transport: Endocytosis
Endocytosis occurs when the cell
surrounds and takes in large material from
it’s environment
Does not pass through membrane
Engulfed and enclosed by part of the PM
Membrane breaks away creating a vacuole with
the material inside


Phagocytosis: cell brings in a solid
Pinocytosis: cell brings in liquid
Active Transport: Exocytosis
Exocytosis occurs when the cell expels or
secretes large particles from the cell

Ex. wastes, hormones
Show Me What You Know
Water moves into a cell placed in a(n)
__________ solution.
A. Osmotic
B. Hypertonic
C. Hypotonic
D. Isotonic
Show Me What You Know
Water moves into a cell placed in a(n)
__________ solution.
A. Osmotic
B. Hypertonic
C. Hypotonic
D. Isotonic
Show Me What You Know
Water moves out of a cell if the cell is placed
in a(n) ___________ solution.
A. Hypertonic
B. Isotonic
C. Hyptonic
D. passive
Show Me What You Know
Water moves out of a cell if the cell is placed
in a(n) ___________ solution.
A. Hypertonic
B. Isotonic
C. Hyptonic
D. passive
Show Me What You Know
A cell moves particles from a region of
lesser concentration to a region of
greater concentration by ____________.
A. Facilitated diffusion
B. Passive transport
C. Osmosis
D. Active Transport
Show Me What You Know
A cell moves particles from a region of
lesser concentration to a region of
greater concentration by ____________.
A. Facilitated diffusion
B. Passive transport
C. Osmosis
D. Active Transport
Activity
Write a summary for your notes
Create a foldable to be glued into the
activity page of your notebook. Use p. 195
of your text to create the foldable. Don’t
forget to use at least 4 colors

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