Transcript Plasma Membrane

The Plasma (Cell)
Membrane -
Gateway to the Cell
Photograph of a Cell
Membrane
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Key Vocabulary:
• Homeostasis: A Balanced
internal condition of the cell
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Functions of Plasma
Membrane
Regulate transport in & out of cell
And many more jobs: Allow cell
recognition, provides anchoring sites for
filaments of cytoskeleton, binding sites
for enzymes, and binds cells together
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Structure of the Cell
Membrane
Membrane Components
Phospholipids
Proteins
other parts
Can you name the main parts?
Phospholipid bilayer
Cell Membrane
** The heads are hydrophilic (water loving)
** The tails are hydrophobic (water fearing
Cell Membrane
Hydrophobic molecules pass easily;
hydrophilic do not.
This is called selectively permeable.
Selectively permeable
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Semipermeable Membrane
Small molecules and larger hydrophobic
molecules move through easily.
e.g. O2, CO2, H2O
Semipermeable Membrane
Large molecules such as proteins do not move
through the membrane on their own.
FLUID MOSAIC MODEl
Animation
• http://www.susanahalpine.com/anim/Life/m
emb.htm
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Label
Cell Membrane Model
• Phospholipids
– Hydrophobic
– hydrophilic
• Proteins
• Cytoplasm
• Outside cell
Level 4
• Add
– Carbohydrates
– cholesterol
– More proteins
– cytoskeleton
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Stop Here
What do you remember?
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Types of Transport
Across Cell
Membranes
TWO TYPES OF
TRANSPORT
• PASSIVE
– NO ENERGY
REQUIRED
• ACTIVE
– ENERGY
REQUIRED
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PASSIVE TRANSPORT:
Simple Diffusion
• Molecules
move from
area of HIGH
to LOW
concentration
Diffusion of Liquids
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Diffusion through a
Membrane
Cell membrane
PASSIVE TRANSPORT:
Osmosis
• Diffusion of
WATER across a
membrane
Diffusion across a membrane
Semipermeable
membrane
Diffusion of H2O Across A
Membrane
PASSIVE TRANSPORT : Facilitated Diffusion
Molecules will randomly move through
the pores in Channel Proteins.
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http://www.pbslearningmedia.org/resource/tdc02.sci.life.cell.m
embraneweb/cell-membrane-just-passing-through/
Molecule
Through what part of the cell
membrane?
Oxygen
Carbon Dioxide
Water
Glucose
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STOP HERE
TWO TYPES OF
TRANSPORT
• PASSIVE
– NO ENERGY
REQUIRED
• ACTIVE
– ENERGY
REQUIRED
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Active Transport
Requires energy or
ATP
Moves materials from
LOW to HIGH
concentration
AGAINST
concentration gradient
Example:Sodium-Potassium
Pump
3 Na+ pumped in for every 2 K+
pumped out.
Moving the “Big Stuff”
Exocytosis
- moving
things
out.
Molecules are moved out of the cell by vesicles that fuse
with the plasma membrane.
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Endocytosis – Phagocytosis
Used to engulf large particles such as
food, bacteria, etc. into vesicles
Phagocytosis About to Occur
Exocytosis
The opposite of endocytosis is exocytosis. Large
molecules that are manufactured in the cell are
released through the cell membrane.
Inside Cell
Cell environment
Stop Here
Types of Solutions
• Isotonic
• Hypotonic
• Hypertonic
Cell in Isotonic Solution
10% NaCL
90% H2O
ENVIRONMENT
CELL
10% NaCL
90% H2O
NO NET
MOVEMENT
What is the direction of water movement?
equilibrium
The cell is at _______________.
Cell in Hypotonic Solution
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?
Cells in Solutions
Isotonic Solution
NO NET
MOVEMENT OF
H2O (equal amounts
entering & leaving)
Hypotonic
Solution
The cell
expands
Hypertonic
Solution
The cell shrinks
Osmosis in Red Blood Cells
Isotonic
Hypotonic
Hypertonic
What Happens to Blood Cells?
hypotonic
hypertonic
isotonic
hypertonic
isotonic
hypotonic
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