Transcript Plasma Membrane - Phoenix Union High School District

The Plasma Membrane -
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Photograph of a Cell
Membrane
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Cell Membrane
The cell
membrane
controls what
comes into
and goes out
of a cell.
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Structure of the Cell
Membrane
Phosphate Heads
Surface Protein
Surface Protein
Lipid Tails
Transport (Channel)
Protein
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Phospholipid Bilayer
Phospholipids are arranged in a bilayer,
with the tails facing inward and the
heads facing outward.
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
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Phospholipids
Phosphate Head
Hydrophilic or
“Water-Loving”
Polar
Lipid Tail (fatty acid)
Hydrophobic or
“Water-fearing”
Non-polar
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Cell Membrane
Heads are hydrophilic “water loving”
Tails are hydrophobic “water fearing”
Makes membrane “Selective”
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Selective Permeability
These molecules pass easily;
EX.
O2, CO2, H2O
they pass through the lipids
These DO NOT
EX. Ions, proteins
they can’t pass through the lipids
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The Cell Membrane is Fluid
Molecules in cell membranes are
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constantly moving
and changing.
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The Membrane is called the
Fluid Mosaic Model
– Parts of the membrane “float” around
and are NOT fixed in place
– It has proteins on the surface and
through it
http://www.bio.davidson.edu/people/macampbell/111/memb-swf/membranes.swf
Membrane Proteins
• Peripheral proteins
are attached on the
surface
• Integral proteins
span the entire
membrane.
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Membrane Protein Functions
• Peripheral proteins
–
–
–
–
Hormone binding sites
Enzymes
Cell adhesion
Cell to cell communication
• Integral proteins
– Channels for passive
transport
– Pumps for active
transport
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GLYCOPROTEINS
Recognize
“self”
Glycoproteins have carbohydrate tails to act as
markers for cell recognition & cell signaling. 13
CHOLESTEROL
Cholesterol helps maintain structural stability.
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Cell Membrane
The cell
membrane
controls what
comes into
and goes out
of a cell.
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Homeostasis
• Balanced internal environment
of cells
• Also called equilibrium
• Maintained by plasma membrane
controlling what enters & leaves
the cell
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How does the plasma
membrane maintain
homeostasis?
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Three Forms of Transport Across the Membrane
Materials move across
the bilayer from a HIGH
concentration to a LOW
concentration.
Materials move through a
Transport Protein from a
HIGH concentration to a
LOW concentration.
Materials move through a
Transport Protein from a
LOW concentration to a
HIGH concentration.
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(REQUIRES ENERGY)
Substances crossing the
membrane WITHOUT the use
of energy.
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First, some REVIEW words.

DIFFUSION
The passive movement of particles
from an area of high concentration to
an area of low concentration
OSMOSIS
The passive movement of water from
an area of lower solute concentration to
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an area of higher solute concentration
Let’s review a couple of
words. 
Solution: A mixture of 2 or more
substances
Solute: the substance that is
dissolved
Solvent: the substance in which the
solute is dissolved
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Examples
salt and
In saltwater, the solute is ______
water
the solvent is _________.
In Kool-Aid, the solutes are the
powder
sugar
______________
and _____________.
water
The solvent is ___________
.
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Diffusion
• Requires NO
energy
(passive)
• Molecules
move from
area of HIGH
to LOW
concentration
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Diffusion of Liquids
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Diffusion through a
Membrane
Cell membrane
Solute moves from HIGH concentration to LOW concentration
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Passive Transport
Simple Diffusion
Examples:
Oxygen diffusing into
a cell
carbon dioxide
diffusing out.
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Osmosis
Diffusion across a membrane
• Diffusion of water
across a
membrane
• Moves from HIGH
water
concentration
(low solute) to
LOW water
concentration
(high solute) copyright cmassengale
Semipermeable
membrane
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Diffusion of H2O Across A
Membrane
High H2O concentration
Low H2O concentration
Low solute concentration
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High solute concentration
3 types of solutions
Hypertonic
Hypotonic
Isotonic
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“hyper” = above
Hypertonic solution= has a higher
concentration
Hypertonic Solution
4% sugar
solution
cell
2% sugar
“hypo” = below
Hypotonic solution= has a lower
concentration
Hypotonic Solution
cell
2% sugar
1% sugar solution
“iso” = equal
Isotonic solution= has the same
concentration
Isotonic Solution
cell
2% sugar
2% sugar solution
Ok, let’s practice what we’ve just
learned . . .
Number 1 - 8 on your paper.
Hypotonic
1. _________?
Solution
Practice
cell
2% sugar
1% sugar solution
Isotonic
2. _________?
Solution
Practice
cell
2% sugar
2% sugar solution
Hypotonic
3. _________?
Solution
Practice
cell
7% sugar
5% sugar solution
Practice
Jose dissolves 1 gram of
gelatin powder into 100 mL
of water and pours it into
the beaker below.
1.0%
gelatin
solution
4. What is the
solvent in this
solution?
______
Water
5. What is the solute
in Jose’s solution?
Gelatin Powder
______
1.0%
gelatin
solution
Practice
Hypertonic
6. _________?
Solution
1.5% sugar
solution
Practice
cell
1.0% sugar
7. Which solution is
hypertonic?
Practice
The outside one
3.8% sugar
solution
cell
3.2% sugar
Practice
8. Which solution is hypotonic?
Inside the cell
1.5% sugar
solution
cell
0.5% sugar
End Practice
3 types of solutions
Hypertonic
Hypotonic
Isotonic
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Diffusion of H2O Across A
Membrane
High H2O concentration
Low H2O concentration
Low solute concentration
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High solute concentration
So, how does this affect
CELLS?
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Osmosis in Red Blood Cells
Isotonic
Hypotonic
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Hypertonic
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Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
Shrivels!
CELL
5% NaCL
95% H2O
What is the direction of water movement?
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Cell in Hypotonic Solution
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
Explodes!
What is the direction of water movement?
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Cell in Isotonic Solution
10% NaCL
90% H2O
ENVIRONMENT
CELL
10% NaCL
90% H2O
Stays the
same!
What is the direction of water movement?
equilibrium
The cell is at _______________.
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Isotonic Solution
Hypotonic
Solution
NO NET
MOVEMENT OF
H2O (equal amounts
entering & leaving)
Water IN
Cell explodes!
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Hypertonic
Solution
Water OUT
Cell shrivels!
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Tonicity and Osmosis
Worksheet
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Passive Transport
Facilitated diffusion
Doesn’t require energy
Uses transport
proteins to move high to
low concentration
Examples: Glucose or
amino acids moving from
blood into a cell.
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Facilitated Diffusion
Molecules will diffuse through the
Integral Proteins.
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Substances crossing the
membrane WITH the use of
energy.
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Active Transport
Requires energy or
ATP
Moves materials from
LOW to HIGH
concentration
AGAINST
concentration gradient
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Active transport
Examples: Pumping
Na+ (sodium ions)
out and K+
(potassium ions) in
against the
concentration
gradient.
Called SodiumPotassium Pump
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Sodium-Potassium Pump
ActiveTransportDemo
3 Na+ pumped in for every 2 K+ pumped out
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Three Forms of Transport Across the Membrane
Materials move across
the bilayer from a HIGH
concentration to a LOW
concentration.
Materials move through a
Transport Protein from a
HIGH concentration to a
LOW concentration.
Materials move through a
Transport Protein from a
LOW concentration to a
HIGH concentration.
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(REQUIRES ENERGY)
What about the big
stuff?
Endocytosis
–
Exocytosis
– large substances
large substances
coming in; infolding of the
membrane.
going out; vesicles fuse with the
membrane
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Endocytosis
Cells taking in materials, forming
vesicles.
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Endocytosis
1. Pinocytosis – taking in liquids
“Cell Drinking”
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Example of Pinocytosis
mature transport vesicle
pinocytic vesicles forming
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Also called “Cell Drinking”
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Endocytosis
2. Phagocytosis – taking in solids
“Cell Eating”
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Endocytosis – Phagocytosis
Used to engulf large particles such as
food, bacteria, etc. into vesicles
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Phagocytosis About to Occur
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Phagocytosis
- Capture
of a Yeast
Cell (yellow)
by
Membrane
of an
Immune
System Cell
(blue)
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Exocytosis
Molecules are moved out of the cell by
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vesicles that fuse with the cell membrane.
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Exocytosis
Exocytic
vesicle
immediately
after fusion
with plasma
membrane.
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What about the big
stuff?
In each of these cases, the
membranes are able to form
and break without the loss of
continuity of the plasma
membrane.
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Li Yang & Huey Huang Model
a) Membranes
approach
b) Membranes touch
c) At point of contact,
there is one bilayer.
d) Membranes become
continuous.
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Let’s Review!
•Passive Transport
•Simple Diffusion
•Osmosis
•Facilitated Diffusion
REQUIRES NO ENERGY!
HIGH conc. to LOW conc.
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Let’s Review!
•Active Transport
•Pump
•Endocytosis
•Phagocytosis
•Pinocytosis
•Exocytosis
REQUIRES ENERGY
LOW conc. to HIGH conc.
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