This causes the glucose-rich region to fill up with water. Osmosis makes plant cells swell up if they are surrounded by a weak solution, and they become turgid, the water molecules enter the plant cells. In a strong solution, the plant cells would shrink because the water molecules are leaving the plant cells. Aim: To investigate the effects of different concentrations of sugar solutions on potato cells by measuring the change in weight of potato tubes after placing them in the solutions for a measured amount of time. What I Will Change: The concentration of sugar will be the only controlled variable in this experiment; this will be prepared by making a molar sugar solution and diluting it with variable quantities of distilled water, as follows.
The transport of materials against a concentration gradient requires energy, so it is called active transport. Aim Our aim was to find out how sugar solution strength affects osmosis, we did this by doing an experiment and then got the results. The results are as expected the 2m solution has made the potato pieces in the jar shrink. The experiment has proven that the stronger the solution is the more it affects the rate of osmosis in a semi-permeable membrane. The aim that we had was proved right and sought out to investigate osmosis in a more detailed way for us to find out more information about it.
An Investigation into the Factors which Affect Osmosis Osmosis is defined as the movement of water molecules from a higher concentration to a lower concentration through a partially permable membrane. Osmosis occurs with molecule moving in and out, these molecules move across the plant’s cell membrane. The plant’s cell membrane is partially permable and therefore it has small holes in it which allow for small water molecules to pass through it however larger molecules such as glucose through. However on the out side of the plant cells there is a cell wall of cellulose that has larger holes that let anything pass through it. This cell wall is totally permeable and therefore will allow larger molecules such as glucose through it, but the larger molecules can still not pass the cell membrane.
A solution that has a lower solute concentration than is present in cells is said to be a hypotonic or hypo-osmotic solution. In this case, excess water flows into the cells and the cells swell. These cells may eventually rupture or burst open. This process is called lysis. Although we simplify osmolarity problems by using the % of a solute to
I kept the variables, such as temperature and volume of sugar solution the same each time to make my test fair. I could extend this coursework by experimenting with surface area and size by using different sized borers and lengths. I could also see how the rate of osmosis is different when using a synthetic potato cell, such as visking tubing. I could also use different sugars, such as glucose and fructose and see how the rate of osmosis changes. I could experiment with different types of potatoes and the altered rate of osmosis in them.
However, they both dissolve in different ways. The intermolecular forces holding molecules of sugar together are quite weak so when sugar is placed in water these bonds are broken and individual molecules are released into solution. It takes energy to break bonds between the molecules and it also takes energy to break the hydrogen bonds in water. These hydrogen bonds have to be disrupted in order to insert a sugar molecule into the substance. The energy needed for this is produced by the forming of bonds between slightly polar sucrose molecules and polar water molecules.
But in a low concentration of water the amount of solute (e.g. sugar) is high. These solutions are usually known as concentrated or strong solutions. When a weak solution and a strong solution are separated by a partially permeable membrane, the water will move from the area of high concentration to the area of low until both sides are equal. This is osmosis, and is shown in the diagram below.
In the example below sugar molecules represent the soluble. Cell sap is contained in the vacuole of a cell and is a part glucose, part water solution. The membrane of the cell acts as a semi-permeable membrane across which osmosis occurs (see below). In the case of osmosis into and out of the vacuole, it occurs across two membranes - the plasmalemma and the tonoplast. When osmosis occurs, water may enter or leave the vacuole according to the concentration of the substances inside and outside the potato cell.
This membrane is called a partially permeable membrane. The amount of water inside a cell is called water potential. Turgor is the name given when osmosis takes place between the cytoplasm and the solution outside the cell. This happens when a plant cell is placed in a high concentrated solution of water, water then passes through the cell wall, the cell membrane, and the cytoplasm and into the vacuole. The increased pressure of water inside the vacuole is called Turgor pressure.
Investigating the Concentration of Sucrose in Cells of Carrots and Potatoes Plan Introduction Osmosis is defined as 'the net movement of water molecules from a region of high water concentration to a region of lower water concentration through a partially permeable membrane'. In my experiment the process of osmosis will be due to the concentration of sucrose inside the cell compared to outside. Therefore if there is a higher concentration of sucrose molecules outside the cell then the net movement of water molecules will be out of the cell and similarly if there is a higher concentration of sucrose molecules inside the cell then the net movement of water molecules will be into the cell. This movement of water molecules causes the cells to become either turgid, which is when the cells are filled with water, or flaccid, which is when the cells are 'limp' with little water. Aim To find the concentration of sucrose in cells of carrot and potato.