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Biology Coursework - Osmosis - To Investigate concentration of sucrose solution is isotonic to potato cell sap.

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Introduction

Biology Coursework - Osmosis Planning Aim: To investigate what concentration of sucrose solution is isotonic to potato cell sap. Apparatus: 0M sucrose (aq) (distilled water) 2M sucrose (aq) Potato Chip cutter Knife Boiling tubes Measuring cylinder (25cm3) Vernier callipers (to nearest 0.1mm) Balance (to nearest 0.01gram) Safety: I will ensure safety around the lab by: wearing safety goggles, laying paper towels, removing baggage from walking space, push stools under the bench, stand up, walk carefully and slowly - don't rush and handle equipment and apparatus carefully. Preliminary Experiment: I did a small experiment before doing the real one so I could find a suitable range to base my investigation round. I used 3 chips in 3 boiling tubes, each containing 20cm3 of: 0M sucrose, 0.5M sucrose and 1M sucrose. Moles of Sucrose /M Original Mass /g Mass after 3 hours /g Up/Down in mass 0M 8.02 9.94 Up 0.5M 8.18 7.83 Down 1M 8.83 7.20 Down As you can see from my preliminary results, I should investigate between 0M sucrose and 0.5M sucrose as a suitable range.

Middle

In all things, everything moves from high concentration areas to low concentration areas, when in water, this process is called 'Osmosis'. With potato (plant) cells, it swells up as water enters via osmosis, however, it won't burst because the cell wall is tough, and it only stretches out slightly. When it can't stretch anymore, it is called 'Tugor'; this is what makes the plant firm and stand up. The opposite, when the cell membrane shrinks to its limit because of lack of water, is called 'Plasmolysis', which makes the plant wilt. Obtaining Moles of Sucrose /M Original Mass /g Mass after 3 hours /g Up/Down in mass Gain/Loss /g 0.1M 9.09 9.94 Up +0.85 0.2M 9.26 9.97 Up +0.71 0.3M 9.07 9.12 Up +0.05 0.35M 9.13 9.06 Down -0.07 0.4M 9.09 8.00 Down -1.09 0.5M 9.58 7.93 Down -1.65 I have made sure my results are fully accurate and I don't see any unusual results or anomalies.

Conclusion

It could be because I didn't dry it enough when I went to measure them after the 3 hours, which I think, is the most plausible one. A part from that, most or all my results were very accurate. I would probably spent more time getting more results than the few I had, and investigated further into the exact concentration that is isotonic to potato cells, which I figure is now between 0.3M and 0.35M sucrose (aq). If I had repeated each concentration about 3 times, I could average them and get a more reliable graph and table of results to base my conclusion on. The potato has approximately have a 0.325M concentration of sucrose in its cells, if I were to put a potato chip in 0.325M solution of sucrose, its size and mass should not change if my results are correct. If both have the same concentration of sucrose, osmosis won't occur, as nothing is higher or lower in concentration. Robert Guillon B10 Osmosis coursework

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Here's what a teacher thought of this essay

4 star(s)

****
A good summary of the investigation but the concise style means that insufficient detail and explanation are included in places. The author has a mostly sound grasp of background theory.

Marked by teacher Adam Roberts 05/09/2013

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