Friday, September 5, 2008

Introduction to Unit 1 Lab 1 Osmosis & Diffusion

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Osmosis & Diffusion
Molecules are in constant motion and tend to move from regions where they are in higher concentration to regions where they are less concentrated. Diffusion is the net movement of molecules down their concentration gradient. Diffusion can occur in gases, in liquids, or through solids.

Osmosis is a specialized case of diffusion that involves the passive transport of water. In osmosis water moves through a selectively permeable membrane from a region of its higher concentration to a region of its lower concentration. The membrane selectively allows passage of certain types of molecules while restricting the movement of others.

Here is a link to demonstration of osmosis:

A few questions to prepare you for the unit:

Which one of the following statements about diffusion is true?

A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition?

Cells A and B are the same size, shape, and temperature, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____.

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