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To find out the effect of sucrose concentration on the mass of a potato cell. To find the concentration of the cell sap in a potato.

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Introduction

Osmosis in a Plant Cell Aim: To find out the effect of sucrose concentration on the mass of a potato cell. To find the concentration of the cell sap in a potato. Introduction: Osmosis is when water passes from a weaker to a stronger solution through a semi-permeable membrane. This happens to decrease the concentration in the stronger solution, and increase it in the weaker solution, creating an equal balance in the two solutions. Water moves in to plant cells in the root hair cells by osmosis. A root hair cell's membrane is semi-permeable, like all plant and animal cell membrane. This allows water to move through into the vacuole of the root hair cell. The water moves from the high water concentration in the soil, to the low water concentration in the cell's vacuole. The root hair cell has a large surface area to make this process more efficient. This experiment looks at the mass change of a potato chip after being immersed in different concentrations of sucrose for a set time. The mass of the potato can decrease or increase in different concentrations depending on the concentration of sucrose in the potato's cell sap. ...read more.

Middle

Cut potato chip to correct size and weight, record these in table. Measure out 25cm� of the sucrose solution (whichever concentration using). 2. Drop potato in solution and start timer. 3. At whatever time period you chose, take out potato and weigh, record new weight. Always dry potato before weighing it. Experiment 1: To find a good immersion time. I will look at the time taken to get a noticeable difference in the mass change of identical potato chips in 25cm� of pure water and 80% sucrose solution. I chose these two as the two extremes here I should see the most mass change for each time bracket. I will chose the immersion times where I get definite masses. Results. Time Mass change pure water Mass change 80% Sucrose 5 10 15 20 25 30 +0.03g +0.05g +0.07g +0.09g +0.11g +0.11g -0.02g -0.07g -0.13g -0.17g -0.19g -0.20g I will use 20 minutes for my immersion time because it is where both extremes have changed a lot, but are changing at a slower rate. Between 20 and 25 minutes there is little change. Experiment 2: To work a suitable range of concentrations. To work out a suitable range of concentrations to give results above and below the concentration of the cell sap. ...read more.

Conclusion

* Not being sufficiently dried. * Not fully immersed I think I did do enough repeats because my mean average did eliminate most odd results. I could have done more data points within my experiment had I been given more time, maybe adding half way marks between percentages. I think the immersion was adequate, but maybe more time would have lead to more accurate results, as long as they weren't too long to be pointless. To make the conclusion more accurate I could use more results, with a closer range or more repeats. Another experiment to investigate osmosis is experiment 2.4 in 'Biology for You' by Gareth Williams. This experiment shows the action of osmosis not by mass change but by the water level rising up a thin tube. Setting up the apparatus as below causes the action of osmosis. The water moves across the visking tubing (which is a semi-permeable membrane) and into the strong solution inside that. The increase in water in this small space causes the water to rise up the glass tube. You could conduct an investigation to find the different rates of osmosis in different concentrations. By measuring how many cms the water travels in a set period of time you could calculate the rate for each concentration to see if there is a difference. ...read more.

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