BB lecture 10-06-08 mem. transport, potential

BB lecture 10-06-08 mem. transport, potential - Chapter 7...

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Chapter 7 (pp. 135-140) – Cell membrane functions (continued) Learning objectives: Explain how cells respond to solutions of different tonicity Describe how an electrochemical gradient (voltage) is established Describe the process of co-transport Explain the modes of bulk transport across a cell membrane Terms to know include… electrogenic pump, cotransport/coupled transport, phago-, pino-, endo-cytosis, recptor mediated endocytosis… ---------------------------------------------------------------------------------------------------------------- Chapter 48 (pp.1050-1061) Cell communication Learning objectives: Define membrane potential ; resting potential . Explain how the sodium-potassium pump helps maintain resting potential. Know the difference between the types of ion channels: ungated and gated, Types of Gated: stretch-gated, ligand-gated, and voltage-gated.
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Tonicity Is the ability of a solution to cause a cell to gain or lose water Has a great impact on cells without walls (i.e., animal cells, protists. .) What does “tonicity” mean…?
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If a solution is isotonic The concentration of solutes is the same as it is inside the cell There will be no net movement of water If a solution is hypertonic The concentration of solutes is greater than it is inside the cell The cell will lose water If a solution is hypotonic The concentration of solutes is less than it is inside the cell The cell will gain water Figure 7.13 Hypotonic solution Isotonic solution Hypertonic solution Animal cell. An animal cell fares best in an isotonic environ- ment unless it has special adaptations to offset the osmotic uptake or loss of water. (a) H 2 O H 2 O H 2 O Lysed Normal Shriveled
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Having a rigid cell wall makes a big difference: Healthy non-woody plants are turgid (erect) Plants that are stressed are flaccid (limp) So, which is best for keeping a plant turgid? a. hypotonic solution b. hypertonic solution c. isotonic solution Remember: If a plant cell is flaccid it is in an isotonic OR hypertonic environment.
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Active transport – 2 important points: 1. Moves substances against their concentration gradient… 2. Requires energy , usually in the form of ATP
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How ATP Performs Work ATP provides the energy to do work By phosphorylation , transferring a phosphate group to another molecule ATP hydrolysis ADP + molecule- P Molecule- P has become phosphorylated
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The Structure and Hydrolysis of ATP ATP (adenosine triphosphate) Is the cell’s energy ‘currency’ ( like $ ) Energy ‘transfers’ w/ this phosphate group Figure 8.8, p.149 O O O O CH 2 H OH OH H N H H O N C HC N C C N NH 2 Adenine Ribose Phosphate groups O O O O O O - - - - CH P P P
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Energy is released from ATP When the terminal phosphate bond is broken
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BB lecture 10-06-08 mem. transport, potential - Chapter 7...

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