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Water Potential Of Potato Cells

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Water Potential & Osmosis - Investigative Coursework Background Research: Diffusion is the net movement of molecules from a region of higher concentration to a region of lower concentration. This occurs until the molecules are evenly spread out and no more collisions can take place. Fick's Law Of Diffusion Fick's law of diffusion is used to measure the rate of diffusion. It states that: The rate of diffusion = surface area x concentration difference thickness of membrane This suggest that the rate of reaction will be faster when the surface area and concentration difference is larger and the membrane is thinner. When carrying out my experiment, I must bear in mind Fick's law and use the equation to maximise the surface area of my potato chips so that the rate of reaction is faster. The Collision Theory (Temperature (�C), Concentration & Kinetic Energy) Increasing the temperature of a reaction, increases the rate of reaction. As does increasing the concentration of a particular solution within a reaction When potato cells are placed in a water solution and the temperature is increased, this increases the rate that osmosis occurs through the partially permeable membrane. Explanation -Particles can only react when they collide. -Heating a substance causes the particles to gain more kinetic energy. -This causes the substrates to bind and collide more frequently with the active site of the enzyme (phospholipids in potato cells), resulting in more successful enzyme-substrate complexes and therefore a faster reaction. -However the rate of reaction only increases up to the optimum temperature (around 43 degrees for potato cells) -The optimum temperature is the temperature at which the rate of reaction is fastest. -Above the optimum temperature the enzyme begins to denature, which results in the hydrogen and ionic bonds breaking thus causing the tertiary structure of the enzyme to change. -This causes the enzyme (phospholipd proteins) to change shape and osmosis can no longer occur. ...read more.


Hair should be tied back in any scientific experiment. Equipment Equipment must be used for its purpose and also safely. This helps to avoid any unnecessary injuries and accidents. Apparatus Quantity Apparatus Reason For Use/Information 1 6mm Cork Borer For cutting the potatoes into cylinder type shapes, as close to all of them being even. 2 Potato Key resource for entire investigation. 6 Boling Tubes Needed to accommodate the varying salt concentrated solutions 6 250ml Measuring Beakers For accurately measuring the amount of distilled water and salt solution needed to establish the correct concentration. - 300 ml Distilled Water Needed to create the different concentrations of salt solution (0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 molar). - 300 ml Salt Solution Needed to create the different concentrations of salt solution (0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 molar). 6 Potties The solutions must be left for 20 hours to allow osmosis to occur. Potties will be used to avoid evaporation of the solution. 12 Pins These are needed for the divided potato cylinders. 1 Balance A balance is needed to accurately measure the mass of the potato chips before and after the experiment 1 White Tile Used as a flat, clean surface area. A white tile prevents the potato cell from colliding with other substances on table surfaces. 1 Pair Goggles Health and safety requirement. These help avoid damage to the eyes in particular. The salt solution could be an issue which could be easily prevented by using goggles. 1 Calliper An accurate measuring device which will measure the length and width of the potato chips. This device helps to avoid human error since the human eye is not very precise. 1 Scalpel For cutting the potato pieces. This device can allow very accurately cuts. 1 Boiling Tube Holder Used to hold and arrange the six boiling tubes needed for the investigation. 1 Stopwatch Needed to time the investigation and keep the test as fair as possible. ...read more.


10 1 Finishing Mass (g) 11 2 Total Mass Change (g) +1 +1 Total Mass Change (g)/Starting Mass (g) = Percentage Change In Mass (%) 1/10 x 100 = 10% 1/1 x 100 = 100% Overall Percentage Change In Mass (%) 10% Increase 100% Increase The table shows that each potato started of at different masses (g) and finished at different masses (g). However the total mass change (g) is the same for both potatoes. This figure does not take into account the proportion/percentage of actually how much each potato has increased by. As the table suggests finding the total mass change (g) only shows how much that particular potato has increased or decreased by. In contrast, the total mass does not show the percentage change when compared to another potato of different mass. Obviously it will be very difficult to make each potato cylinder exactly the same length & mass so I will have to use the total mass change (g) and the starting mass (g) (working formula showed below) to calculate the percentage change (%). Percentage Change In Mass = Change in mass Initial mass x 100 What will I do with my collected data? I will use my data in various ways to help generate conclusions. First of all I will plot my data within a graph to establish any hidden patterns within the data itself. An example of the type of graph I will use to plot my results is shown below. Once my results are plotted on this graph. I will be able to establish how the water potential of a potato cell changes in mass at different concentrations of salt solution. I will use a graph similar to the one above. This graph will help me to determine water potential (?)of potato cells and draw conclusions. I will use my results to plot a graph similar to the one above. I am to establish where the line of best intercepts the x-axis (example shown above) since this will signify the where the concentration solution is isotonic (neither increased or decreased in mass (g)). ?? ?? ?? ?? ...read more.

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