230-3-SciInvestOsm - Bio 230 Scientific Investigation:...

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Bio 230 Scientific Investigation: Osmosis INTRODUCTION Humans have always sought explanations of things and processes. In Cell Biology we study the molecular basis of cellular and organismal function. Careful observation, the key to science, requires collection of data about the real world. Many discoveries in cell biology have come about because of advances in the technology of observation; examples include microscopes, spectrophotometers, fluorescent-tagged antibodies, and automated DNA sequencers. After making observations (collecting data) you propose an hypothesis, a general principle that tells "why" or "how" and explains and unifies all the observations. A scientific hypothesis must be testable. If the hypothesis is valid, certain events or results of experiments are expected to occur. A good hypothesis lends itself to experiments designed to disprove it. In today's lab the class will do some simple science related to an important physical phenomenon all cells must deal with: osmosis. PROCEDURES Complete your assignment on a separate sheet (81/2 x 11") using the format given (parts numbered and lettered correctly, and in correct numerical order, but please do not write out the assignment questions! ). If you work carefully you can do most of the assignment in its final form while in lab. If you prefer to type your assignment, be sure that all original work from lab is attached in the correct numerical place on your assignment. This may require that it be cut out and taped in place. Due to the time required for cells to fully respond to their environment, the class will prepare solutions and set up a series of treatments of Elodea leaves before discussing the principles involved, developing hypotheses and "planning" experiments! Step 1. One group will prepare beakers 1-3; remaining groups will each prepare one beaker, using 2% NaCl or 20% sucrose stocks for a total volume of 30 ml. Write your dilution protocol on the board . BEAKER SOLUTION BEAKER SOLUTION 1 water 8 10% sucrose 2 2% NaCl 9 8% sucrose 3 20% sucrose *10 1% NaCl, 12% sucrose 4 1% NaCl *11 0.8% NaCl, 10% sucrose 5 0.8% NaCl *12 0.6% NaCl, 8% sucrose 6 0.6% NaCl (*note each concentration is the 7 12% sucrose final concentration)
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This note was uploaded on 10/23/2010 for the course PHYS 220 taught by Professor Koskelo during the Spring '08 term at Skyline College.

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230-3-SciInvestOsm - Bio 230 Scientific Investigation:...

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