Aim: How cell membrane organized?

HW #101. Complete the handout on the cell

Do now: You have 5 min.1.Explain how the following structures:

a. Nucleolusb. Ribosomesc. Endoplasmic reticulumd. cytoplasm

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The Plasma Membrane

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Photograph of a Cell Membrane

I. Cell Membrane A. General

1. Flexible and allows a unicellular organism to move

1. Maintain a high concentration of materials in the cell.

2. Keep harmful materials out.

3. Control the movement of materials into and out of the cell.

4. Let the cell sense its environment.

B. Function

5. Protective barrier

6. Regulate transport in & out of cell (selectively permeable)

7. Allow cell recognition

8. Provide anchoring sites for filaments of cytoskeleton

Membrane Components

Proteins Are Critical to Membrane Function

9. Provide a binding site for enzymes

10. Interlocking surfaces bind cells together

11. Contains the cytoplasm (fluid in cell)

C. Maintains homeostasis

1. Balanced internal condition of cells.

Also called equilibrium

2. Maintained by plasma membrane controlling what enters & leaves the cell.

Review1.Explain what would happen to a cell if the cell membrane did not do its job properly.

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D. Structure of the Cell Membrane

Phospholipids

Cholesterol

Proteins (peripheral & integral)

Carbohydrates (glucose)

1. Membrane Components

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a. Phospholipids

1. Make up the cell membrane

a. Contains 2 fatty acid chains that are nonpolar

b. Head is polar & contains a –PO4 group

1. FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid.

2. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.

FLUID MOSAIC MODEL

Polar heads are hydrophilic “water loving”

Nonpolar tails are hydrophobic “water fearing”

Cell Membrane

Makes membrane “Selective” in what crosses

Cell Membrane

Hydrophobic molecules pass easily; hydrophillic DO NOT

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

Solubility

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

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Small molecules and larger hydrophobic molecules move through easily.e.g. O2, CO2, H2O

Semipermeable Membrane

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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