Sample Essay- Exam I

Sample Essay- Exam I - 1 Discuss the differences among...

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1. Discuss the differences among diffusion, facilitated diffusion, active transport, and endocytosis. Provide examples of substances that use each of the above mechanisms to cross the plasma membrane. (50 points) Answer (and grading guideline followed by TAs) Simple diffusion : something that is nonpolar and small can cross the membrane along (with) (down) its concentration gradient (from the side of the membrane where it is in higher concentration to the side where it is in lower concentration). Examples of this would be O 2 , CO 2 (accept other correct examples in all cases) (~ 13 points) . Facilitated diffusion : a substance is also moving across the membrane down its concentration gradient, but it needs to move through a channel or in a transporter because it is polar or a bit larger. Examples: glucose, sucrose. (another example can be water- although this works as an example for simple diffusion also). Both simple and facilitated diffusion are passive transport- they do not require energy to occur
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This note was uploaded on 10/27/2010 for the course BIO 102 taught by Professor Alaie during the Fall '08 term at CUNY Hunter.

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Sample Essay- Exam I - 1 Discuss the differences among...

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