• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Water Potential Of Potato Cells

Extracts from this document...


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.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Molecules & Cells section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Molecules & Cells essays

  1. Marked by a teacher

    An investigation to examine the effects of temperature on membrane stability in beetroot, by ...

    3 star(s)

    pigment within those samples will have had more time in which to leak out of the cells and so the percentage of light that is able to pass through these samples will be less than it should be. However, if some have been left in for a shorter period of


    Water absorption causes the symplast to push against the cell wall so as to create a positive hydrostatic pressure, or turgor pressure that is necessary for cell growth and the support of young, non-lignified tissues. Water potential is always measured as a negative number; this is because the water potential

  1. An experiment to find of the isotonic point of root vegetables cells in contents ...

    % difference Mass before (g) Mass after (g) % difference 0.4 30 29 -3.33 1.3 1.5 0 0.45 30 30 0 1.3 1.3 0 0.5 30 27 -10 1.3 1.3 0 0.55 30 29 -3.33 1.3 1.2 -7.69 0.6 30 28 -6.67 1.3 1.3 0 From my results I can make a prediction that the isotonic point value

  2. Investigation of the effect of adding different concentrations of NaCl to an enzyme-substrate (amylase-starch) ...

    They usually act as carriers, carrying chemical groups of atoms from one active site of one particular enzyme to the active site of another enzyme. Coenzymes that are tightly bound to enzymes are called prosthetic groups. They carry out the same function as coenzymes and can be thought of as 'built in' coenzymes.

  1. Experiment to investigate the water potential of potato tissues when immersed in various sucrose ...

    In the case of the potato tissue being immersed in a solution of lower water potential (i.e. 1M sucrose solution), water molecules will leave the cell by osmosis as the tissue will now have a higher water potential relative to its external solution.

  2. Investigating Osmosis.

    solutions - here different results for each cylinder pulled the average upwards by a noticeable amount, a problem that possibly would not occur if more measurements were taken. For future experimentation we could repeat this experiment using a range of solution strengths very close to the value discovered here of sap osmolarity, to define more exactly its true value.

  1. prove Boyles Law

    For a school experiment, only 10 - 15 results are needed but for a professional experiment 1000s of results would be needed. This is to make sure that no mistakes were made but for a school experiment, we can check our results with past years of the experiment and with results from a textbook.

  2. Catalyse Investigation

    As the temperature continues to rise, however, the hydrogen and ionic bonds, which hold the enzyme molecules in shape, are broken. If the molecular structure is disrupted, the enzyme ceases to function as the active site no longer accommodates the substrate.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work