Investigating the Difference in Isotonic Point in Sweet and White Potato

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  • Topic: Potato, Sweet potato, Starch
  • Pages : 10 (3271 words )
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  • Published : February 28, 2013
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Investigating the Difference in Isotonic Point in Sweet and White Potato Research Aim:
To observe whether equal sized white potato or sweet potato cores reached the isotonic point in the same concentration of sucrose solution. Introduction:
Osmosis is diffusion of water from areas of high water potential to areas of low water potential. It does not require an input of energy. Plants use osmosis to transport minerals from their roots to their leaves, and to take in water in the soil. Because the plant cell is taking in water and minerals, its mass increases. The Maryland Department of Natural Resources states that “plants use water to carry moisture and nutrients from the roots to he leaves and food from the leaves back down to the roots.” (http://www.dnr.state.md.us/forests/education/needs.html) An isotonic point is the moment when the solutions inside the cell and outside the cell have the same water potential since the two have an equal concentration of water molecules. This is when the rate of water leaving the cell is the same as the rate of water entering the cell. Therefore, equilibrium is reached. This means that the plant cell will not increase any more in mass, as there will be no net movement of water. In my experiment, I will be using two different types of potato – the sweet potato and the white potato. I think that it will be interesting to see whether the Sweet Potato is actually sweeter than the White potato (as the name suggests). The sugar content in sweet potatoes is 4.2 grams for every 100 grams you ingest. The sugar content for white potatoes is also 4.2 grams (per 100g). Hypothesis:

The isotonic point of sweet potato will be at a higher sucrose concentration than white potato because I think that it actually does contain more sugar than white potato. Null Hypothesis: There will be no difference in the isotonic points. Method:

Equipment
* Sweet potatoes
* White potatoes
* White tile for cutting on
* 5 Stop Watches, each set for 30 minutes +/- 0.05 seconds + reaction time (215 milliseconds) + time taken for us to start removing the potato cores from the sucrose solution (10 seconds) * Balance +/- 0.005g

* Paper towels
* 10 50ml glass beakers
* Core borer (diameter=1cm)
* Ruler +/- 0.05cm
* Pins for colour coding
* Scalpel
* A flat surface
* 100ml Measuring Cylinder +/- 0.5ml
* 100ml Distilled Water (0.00mol/dm³)
* 100ml 0.25mol/dm³ sucrose solution
* 100ml 0.5mol/dm³ sucrose solution
* 100ml 0.75mol/dm³ sucrose solution
* 100ml 1mol/dm³ sucrose solution
* Thermometer +/- 0.5°C
Method
* Cut out 25 cylinders from each type of potato using the core borer. * Using a scalpel, plate to cut on and a ruler cut each of these down to 2cm each (+/- 0.05cm). * Using the measuring cylinder, put 50ml distilled water in 2 different beakers, and then do the same with each concentration of sucrose solution. * Measure the mass of each potato core using the balance, noting it down and colour coding with a coloured pin. * Put 5 white potato cores into the first beaker (with the distilled water) and do the same with 5 sweet potato cores simultaneously. As you do this, start the stop watch (that should have been set for 30 minutes). * 5 minutes later, add the next 10 potato cores to the next two beakers (the 0.25mol/dm³ sucrose solution) and start the next stop watch. * Repeat this every 5 minutes, until all of the potato cores have been added to their beakers. * When the first stop watch gets to 0 (i.e., when the potato cores have been in for 30 minutes), take out the potato cores from the distilled water. * For each one, dry it using a paper towel with 2 full rolls and a blot on each end. * Measure the mass of the potato cores, noting the change in mass for each one. * Repeat this with every concentration of sucrose solution, when their stop watches go off. * Find the average change in mass for...
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