Plasma Membrane-Gateway to the Cell

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The cell membrane is made of 2 layers of phospholipids called the lipid bilayer

Slide 15

Solubility

Materials that are soluble in lipids can pass through the cell membrane easily

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Semipermeable Membrane

Small molecules and larger hydrophobic molecules move through easily.

e.g. O2, CO2, H2O

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Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own.

Semipermeable Membrane

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Types of Transport Across Cell Membranes

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Simple Diffusion

Requires NO energy

Molecules move from area of HIGH to LOW concentration

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DIFFUSION

Diffusion is a PASSIVE process which means no energy is used to make the molecules move, they have a natural KINETIC ENERGY

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Diffusion of Liquids

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Diffusion through a Membrane

Cell membrane

Solute moves DOWN concentration gradient (HIGH to LOW)

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Osmosis

Diffusion of water across a membrane

Moves from HIGH water potential (low solute) to LOW water potential (high solute)

Diffusion across a membrane

Semipermeable membrane

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Diffusion of H2O Across A Membrane

High H2O potential Low solute concentration

Low H2O potential High solute concentration

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Aquaporins

Water Channels

Protein pores used during OSMOSIS

WATER MOLECULES

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Cell in Isotonic Solution

CELL

10% NaCL 90% H2O

10% NaCL

90% H2O

What is the direction of water movement?

The cell is at _.

equilibrium

ENVIRONMENT

NO NET MOVEMENT

Slide 27

Cell in Hypotonic Solution

CELL

10% NaCL 90% H2O

20% NaCL

80% H2O

What is the direction of water movement?