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How Does Osmosis Affect Plant Cells?

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Introduction

Aim: The aim of the experiment is to find out how the concentration of the solution will affect the rate at which osmosis occurs. I will use this as a trial run to find out which concentrations and at what time is best to leave the cuttings for the greatest change in mass to occur. Apparatus: * 2 potatoes * 2 250ml beakers * 25ml of sugar * top pan balance * no. 9 core borer * knife * 375ml of distilled water * tablespoon * stopwatch Method: 1. Collect the equipment. 2. Add 125ml of water and 25ml of sugar in one beaker and 150ml of distilled water in the other. 3. Using the size 7 core borer carefully cut 10 equal 3cm strips out of the potato. 4. Using the scalpel cut the cuttings to 5 grams and 3cm stripes, making them as close to one another as possible. 5. Mix the solution with the tablespoon, then add 5 pieces of potato to each beaker, while timing the length of time they are in for to the set times. 6. At every set time measure the length and mass of all the potato cuttings and put it back into the beaker. 7. Record the results into a coherent table. Fair Test: To make my experiment a fair test I will keep the potato cutting at the same length and mass. I will use the same size borer, no. 7, throughout. My cuttings will be taken from the same type of potato and will contain no peel. The volume of the two liquids must also be kept equal. Table of Results: SUGAR SOLUTION (started at 10:45am) TOTAL MASS (grams) TOTAL LENGTH (cm) TIME TAKEN OUT BEFORE AFTER DIFFERENCE BEFORE AFTER DIFFERENCE 30mins 5 4.82 -0.18 3 3.0 0 1h 30 5 4.37 -0.63 3 2.7 -0.3 4h 45 5 4.02 -0.98 3 2.4 -0.6 24h 30 5 4.15 -0.85 3 2.2 -0.8 28h 45 5 3.96 -1.04 3 2.2 -0.8 WATER SOLUTION (started at 10:45am) ...read more.

Middle

Whatever the set time is they must all stay in the same time. Type of plant cell There are different plant cells within a plant. Some plant cells contain more water than others, they all have different concentrations of cell sap therefore the rate of osmosis varies from cell to cell. Use the same potato, one potato and remember to remove the peel, as it contains different cells to the rest of the storage cells that make up a potato. Prediction: I predict that the more dilute the solution (the higher the concentration of water) is, the greater the mass of the potato cutting will be after the set time. The higher the concentration of sugar in the solution is, the more water loss there will be and therefore the lighter the cutting will become. I believe osmosis will occur at a greater rate within the cutting, when there is a greater amount of water than sugar in the solution. This means the cuttings that are put into a higher concentration of water will end up with a larger mass than those put into a higher concentration of sugar. Osmosis is the movement of water from a weaker solution into a stronger solution through a semi-permeable membrane while the other solutions are blocked and unable to pass through the membrane. The water will move from a higher concentration of water to a lower concentration of water through a semi-permeable membrane. For example if there was one side of a semi-permeable membrane with 70% water and another side with 40% water, the side with the greater percentage of water, the 70% side would flow from its higher concentration to the lower concentration to help even out the concentrations to an isotonic point, were both sides will be of equal strength. The water molecules are far smaller than the sugar molecules are therefore they are able to fit through the membrane to the lower concentration. ...read more.

Conclusion

The rate of osmosis would vary from cell to cell and it would be interesting to compare the results and find any links or connections as t o why there are comparisons. Different types of potato (e.g. grown from different areas of the world, under different environments) - I would do a similar investigation as this one only using potato from different environments and climates. Once I find the isotonic solution of the different potatoes I could compare the rate of osmosis within the different cuttings (e.g. I could compare the potato cuttings from a hot climate and from a cold climate and investigate whether there are any connections or patterns with the rate of which osmosis occurs and the environment in which the potato is grown in). Different plants/vegetables (e.g. apple, carrot, etc.) - I could investigate if there is a difference in the rate of osmosis within the different plant/vegetable cells. There would definitely be varying results with the different plants/vegetables, as some are root vegetables (e.g. carrot, potato), some are ground vegetables (e.g. peas) and some are open vegetables (e.g. apples, pears) and each have a different function, for example the function of a root vegetables is to hold all of the nutrients needed to promote the potato seedling to grow without sunlight. Different dimensions and surface areas of a cutting - In the experiment I have just completed I used cuttings of equal dimensions and surface areas, but instead I could very this slightly and vary the dimensions of the cutting which would therefore very the surface area. It would be interesting to see if there was a difference in the rate of osmosis when several cuttings of the same mass, but different dimensions were investigated. My results were fairly accurate and even when they were plotted into a graph I cannot see any obvious anomalies. GCSE Biology Coursework - How Does Osmosis Affect Plant Cells? (Preliminary Work) 5 GCSE Biology Coursework - How Does Osmosis Affect Plant Cells? (Planning) 16 ...read more.

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