Aim How is cell membrane organized HW 10

Aim: How is cell membrane organized? HW #10 1. Complete the handout on the cell Do now: You have 5 min. 1. Explain how the following structures: a. Nucleolus b. Ribosomes c. Endoplasmic reticulum d. cytoplasm

Aim: What is the anatomy and function of the cell membrane? Objectives: -Identify the parts of the cell membrane. -Explain the main function of the cell membrane. -Explain and describe the possible part’s function of cell membrane.

Vocabulary development: -Membrane means a cover. - Hydrophilic is"water-loving. " - Hydrophobic is "water-fearing". - Bilayer is a double layer. - Glycoproteins is a carbohydrate attached to a protein. • - Permeable is the ability of something to pass through a barrier. • - Anatomy is the parts of something. • Semi-Permeable _____________ • • •

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The Plasma Membrane *

I. Cell Membrane A. General 1. Flexible and allows a unicellular organism to move

• Identify and list the different parts or properties of the cell membrane by analyze, looking and using the above two diagram.

• Plasma Membrane • All living cells, prokaryotic and eukaryotic, have a plasma membrane that encloses their contents and serves as a semi-porous barrier to the outside environment. The membrane acts as a boundary, holding the cell constituents together and keeping other substances from entering. • Write and explain the main function of

• The plasma membrane is permeable to specific molecules, however, and allows nutrients and other essential elements to enter the cell and waste materials to leave the cell. Small molecules, such as oxygen, carbon dioxide, and water, are able to pass freely across the membrane, but the passage of larger molecules, such as amino acids and sugars, is carefully regulated by transport proteins embedded in the membrane.

• Write and explain the differences in passage through the cell membrane according to size. • Verbally brainstorm with your partner.

All living cells and many of the tiny organelles internal to cells are bounded by thin membranes. These membranes are composed primarily of phospholipids and proteins and are typically described as phospholipid bi-layers.

In this sketch, the spheres represent the phosphate end, which is polar and water soluble (hydrophilic). The twin extensions represent the fatty acid components which are not water soluble (hydrophobic).

• The plasma membrane is composed of a double layer (bilayer) of lipids, oily substances found in all cells. Most of the lipids in the bilayer can be more precisely described as phospholipids, that is, lipids that feature a phosphate group at one end of each molecule.

• Phospholipids are characteristically hydrophilic ("water-loving") at their phosphate ends and hydrophobic ("water-fearing") along their lipid tail regions. In each layer of a plasma membrane, the hydrophobic lipid tails are oriented inwards and the hydrophilic phosphate groups are aligned so they face outwards, either toward the aqueous cytosol of the cell or the outside environment.

• Write and explain how many layers of lipid are used to make a cell membrane? Also, explain the differences between hydrophilic and hydrophobic. • Brainstorm with your partner.

• Within the phospholipid bilayer of the plasma membrane, many diverse proteins are embedded, while other proteins simply adhere to the surfaces of the bilayer. Some of these proteins, primarily those that are at least partially exposed on the external side of the membrane, have carbohydrates attached to their outer surfaces and are, therefore, referred to as glycoproteins.

• The arrangement of proteins also involves the hydrophobic and hydrophilic regions found on the surfaces of the proteins: hydrophobic regions associate with the hydrophobic interior of the plasma membrane and hydrophilic regions extend past the surface of the membrane into either the inside of the cell or the outer environment.

• Where are the proteins located in the cell membrane? • Write your answer and brainstorm with partner.

• Plasma membrane proteins function in several different ways. Many of the proteins play a role in the selective transport of certain substances across the phospholipid bilayer, either acting as channels or active transport molecules.

• Others function as receptors, which bind information-providing molecules, such as hormones, and transmit corresponding signals based on the obtained information to the interior of the cell. Membrane proteins may also exhibit enzymatic activity, catalyzing various reactions related to the plasma membrane.

• Write and list the possible function of the different proteins embedded in the cell membrane.

B. Function 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.

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.

Review 1. Explain what would happen to a cell if the cell membrane did not do its job properly.

D. Structure of the Cell Membrane *

1. Membrane Components Phospholipids Cholesterol Proteins (peripheral & integral) Carbohydrates (glucose)

B. Function 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.

a. Phospholipids 1. Make up the cell membrane a. Contains 2 fatty acid chains that are nonpolar b. Head is polar & contains a –PO 4 group *

FLUID MOSAIC MODEL 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.

Cell Membrane Polar heads are hydrophilic “water loving” Nonpolar tails are hydrophobic “water fearing” Makes membrane “Selective” in what crosses

Cell Membrane The cell membrane is made of 2 layers of phospholipids called the lipid bilayer Hydrophobic molecules pass easily; hydrophillic DO NOT

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

Semipermeable Membrane Small molecules and larger hydrophobic molecules move through easily. e. g. O 2, CO 2, H 2 O *

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

Photograph of a Cell Membrane *