Chapter 7 Section 2 Outline 3t351u

Name: Hunter Davis

Chapter 7 Section 2 Outline The Plasma Membrane Main Idea: The plasma membrane helps to maintain a cell’s homeostasis. Essential Questions: 

How does a cell’s plasma membrane function?

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What are the roles of proteins, carbohydrates, and cholesterol in the plasma membrane?

I. Function of the Plasma Membrane 

The process of maintaining balance in an organism’s internal environment is called homeostasis

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One of the structures responsible for homeostasis is the plasma membrane

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The plasma membrane forms a thin, flexible boundary between a cell and its environment.

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P l a s m a

m embranes have selective permeability meaning they allow some substances to through while keeping other out.

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Control of how, when, and how much of various substances enter and leave the cell depends on the structure of the plasma membrane.

II. Structure of the Plasma Membrane 

The plasma membrane is composed of the phospholipid bilayer.  two layers of phospholipids are arranged tail-to-tail  phospholipids arrange themselves in a way that allows the plasma membrane to exist in the watery environment  the phospholipid heads are water-loving (hydrophilic) and the tails are w a t e r h a ti ng (hydrophobic)

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The plasma membrane also contains cholesterol, proteins and carbohydrates.  Proteins 

Some proteins called receptors transmit signals to the inside of the cell.

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Some proteins serve as structures for the membrane.

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Transport Proteins move needed substances and wastes through the membrane.

 Cholesterol 

Cholesterol prevents the fatty acid tails of the phospholipid bilayer from sticking together.

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Cholesterol contributes to the fluidity of the membrane.

 Carbohydrates

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Carbohydrates define the cell’s characteristics

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Help cells identify chemical signals.

The fluid mosaic model describes the phospholipids in the bilayer as a “sea” in which other components can float and move around.

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The different substances in the plasma membrane create a pattern or mosaic on the surface of the cell.

USE YOUR NOTES AND/OR YOUR TEXTBOOK TO ANSWER THE FOLLOWING QUESTIONS

1. What would happen if the cell membrane were not selectively permeable? your

Then they would not be able to keep out waste and other harmful materials.

response.

2. In the box below, draw the plasma membrane. Include the phospholipid bilayer, cholesterol, proteins, and carbohydrates. Label each part.

3. Describe how the plasma membrane helps maintain homeostasis in a cell. It helps by keeping the inside clean so everybody (the parts of the cell) remains happy and therefore homeostatic.

4. Identify the molecules in the plasma membrane that provide basic membrane structure, cell

Basic membrane structure: Proteins, Carbohydrates, and Cholesterol maintain the structure. Also the phospholipid bilayer.

Cell identity: The cell’s identity is composed of the inner and outer parts, such as the hydrophilic heads, and the hydrophobic tails.

Fluidity: Cholesterol contributes to the fluidity.

identity, and membrane fluidity.