CHAPTER5 - Chapter 5: The Working Cell I. Structure A....

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Chapter 5: The Working Cell I. Structure A. Phospholipid bilayer 1. Hydrophilic heads 2. Hydrophobic tails B. Transport proteins - allow water-soluble substances to move through their interior, which opens on both sides of the bilayer C. Receptor proteins - have binding sites for hormones that can trigger changes in cell action (ex: growth processes) D. Recognition proteins - identify the cell as a certain type and function in cell-to-cell recognition (ex: white-blood cells recognizing bacteria) E. Adhesion proteins - help cells stay connected to one another in a tissue II. Types of membrane transport A. Passive transport 1. Movement of any substance across a membrane without the use of chemical energy 2. Examples: a. Diffusion 1. Movement of molecules from an area of greater/higher concentration to an area of lesser/lower concentration 2. This difference in concentrations is known as the concentration gradient 3. Molecules will continue to diffuse until their concentration is equally distributed = equilibrium 4. Examples: oxygen, carbon dioxide, perfume b. Osmosis 1. Movement of water molecules from an area of greater/higher concentration to an area of lesser/lower concentration 2. Direction of osmosis a. Solutions are composed of two parts: 1. Solute - substance that dissolves 2. Solvent - liquid that dissolves the solutes, usually water 3. Tonicity - refers to the relative concentration of solutes and solvents in two environments/solutions a. Hypotonic environment/solution 1. In the environment, the concentration of solutes is low and the concentration of solvents is high 2. In the cell, the concentration of solutes is high and the concentration of solvents is low 3. The solvents (water) will move into the cell 4. In plants, this causes turgor pressure 5. In animals, it causes cytolysis or cell bursting
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Chapter 5 page 2 b. Hypertonic environment/solution 1. In the environment, the concentration of solutes is high and the concentration of solvents is low 2. In the cell, the concentration of solutes is low and the concentration of solvents is high 3. The solvents (water) will move out of the cell 4. In plants, this causes plasmolysis or cell wilting 5. In animals, this causes crenation c. Isotonic environment/solution 1. The concentrations of solutes and solvents are equal between the environment and the cell 2. There should be an equal movement of water in both directions c. Facilitated diffusion 1. Uses one of the types of transport proteins, channel protein , to move solutes through the membrane
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This note was uploaded on 04/17/2008 for the course BIO 1408 taught by Professor Beechinor during the Spring '08 term at Alamo Colleges.

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CHAPTER5 - Chapter 5: The Working Cell I. Structure A....

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