Ap Bio Lab Report Osmosis
AP Bio Lab Report
Osmosis and Diffusion
Introduction
When a substance is released into an area, the random movement of its molecules results in a multitude of collisions. These collisions, in turn, lead to a dispersion of the molecules. The overall movement of the molecules will be from an area of high concentration, where there will be more collisions, to areas of low concentration, where the number of collisions will be much less. This process of dispersion will continue until there is no net gain or loss of molecules in an area. The process by which this equilibrium occurs is called diffusion. Diffusion is vitally important to biology on many levels; individual cells, organelles, and even whole organisms rely on diffusion to carry out the processes essential to life. One especially important aspect of diffusion is osmosis, or the diffusion of water. This often occurs across a semi-permeable membrane …show more content…
within the cell. Osmosis is special in that its movement is determined by the relative solute concentrations inside and outside of the cell. Because biological systems will move toward equilibrium, the water will move through the membrane, from areas of low solute concentration to areas of high solute concentration, resulting in an equal balance of solute and solvent on either side of the membrane. This lab is helpful in conceptualizing the ideas, applications, and effects of osmosis and diffusion.
Methods A. Diffusion
For this part of the lab, we used a one foot piece of dialysis tubing, 15 mL of glucose-starch solution, 4 mL of iodine potassium iodide (IKI) solution, 4 glucose indicator strips, a graduated cylinder, and a beaker. We began by putting the glucose starch solution into the tied-off dialysis bag. We added 250 mL of distilled water as well as the IKI to the beaker. Before placing the dialysis tubing in the beaker, we determined the glucose content of the glucose-starch solution and the beaker, and also noted the color of both solutions. After thirty minutes, we removed the tubing, and determined the final glucose content of the beaker and bag, and also noted the color of each. Because the glucose is in low concentration outside of the bag, and it is small enough to pass through the membrane, we expected the glucose to diffuse through the bag into the beaker. Similarly, we expected the IKI to also diffuse through the bag. The IKI is an indicator for glucose, and turns dark in its presence. Thus we expected that the tube would darken. B. Osmosis
For the second part of the lab, we used 6ft.
of dialysis tubing, 25 mL of sucrose solutions with concentrations of 0.02 Molar, 0.04M, 0.06M, 0.08M, 1.0M, as well as 25mL of distilled water, six 250 mL beakers, a balance, and paper towels. We first cut the dialysis tubing into 6 pieces, each 1ft. long, and placed them into a beaker of water. We then tied off the dialysis tubing and poured 25 mL of distilled water in. We repeated this with the rest of the five pieces dialysis tubing, pouring a different molarity of sucrose solution in different dialysis tubes. After all the tubes were filled and tied, we then dried the bags and weigh each one on the scale. After all the data was recorded, we filled all the beakers about ¾ full of distilled water, placed the bags into each beaker in unison, and waited 30 minutes. Next, the bags were removed from the beakers, dried, and weighed separately. We expected the mass to increase with increasing molarity because with the higher the concentrations, more water would need to be diffused into the bag to reach
equilibrium. C. Water Potential
The third part of this lab required that we use five 150 mL beakers of different sucrose concentrations; one of 0.2M, one of 0.4M, one of 0.6M, one of 0.8M, and one of 1.0M, as well as 1 beaker of 150mL distilled water. In each beaker we placed four 3cm potato cylinders. The 3cm potato cylinders were bored from a potato and cut into the appropriate length, separating them into 6 groups of 4. However, before placing the cylinders into the beaker, we weighed each group and wrote the data into a table. Each beaker required only 100mL out of the 150mL and so we used a graduated cylinder to measure the 50mL we did not need and dump it out. After acquiring the right amount of solutions in each beaker we placed one group of 4 potato cylinders in each one. After placing the cylinders we proceeded to cover up each beaker with plastic wrap in order to prevent any substance from changing the outcome of the experiment. The beakers were then left over night in order to observe if any changes were made in the mass of the potato cylinders. The next step of the lab was to weigh the cylinders to observe any changes in mass. We had expected the total mass of the group of 4 cylinders to increase because the water would go into the potato to lower the concentration of sucrose and reach equilibrium.
Osmosis and Diffusion
Introduction
When a substance is released into an area, the random movement of its molecules results in a multitude of collisions. These collisions, in turn, lead to a dispersion of the molecules. The overall movement of the molecules will be from an area of high concentration, where there will be more collisions, to areas of low concentration, where the number of collisions will be much less. This process of dispersion will continue until there is no net gain or loss of molecules in an area. The process by which this equilibrium occurs is called diffusion. Diffusion is vitally important to biology on many levels; individual cells, organelles, and even whole organisms rely on diffusion to carry out the processes essential to life. One especially important aspect of diffusion is osmosis, or the diffusion of water. This often occurs across a semi-permeable membrane …show more content…
within the cell. Osmosis is special in that its movement is determined by the relative solute concentrations inside and outside of the cell. Because biological systems will move toward equilibrium, the water will move through the membrane, from areas of low solute concentration to areas of high solute concentration, resulting in an equal balance of solute and solvent on either side of the membrane. This lab is helpful in conceptualizing the ideas, applications, and effects of osmosis and diffusion.
Methods A. Diffusion
For this part of the lab, we used a one foot piece of dialysis tubing, 15 mL of glucose-starch solution, 4 mL of iodine potassium iodide (IKI) solution, 4 glucose indicator strips, a graduated cylinder, and a beaker. We began by putting the glucose starch solution into the tied-off dialysis bag. We added 250 mL of distilled water as well as the IKI to the beaker. Before placing the dialysis tubing in the beaker, we determined the glucose content of the glucose-starch solution and the beaker, and also noted the color of both solutions. After thirty minutes, we removed the tubing, and determined the final glucose content of the beaker and bag, and also noted the color of each. Because the glucose is in low concentration outside of the bag, and it is small enough to pass through the membrane, we expected the glucose to diffuse through the bag into the beaker. Similarly, we expected the IKI to also diffuse through the bag. The IKI is an indicator for glucose, and turns dark in its presence. Thus we expected that the tube would darken. B. Osmosis
For the second part of the lab, we used 6ft.
of dialysis tubing, 25 mL of sucrose solutions with concentrations of 0.02 Molar, 0.04M, 0.06M, 0.08M, 1.0M, as well as 25mL of distilled water, six 250 mL beakers, a balance, and paper towels. We first cut the dialysis tubing into 6 pieces, each 1ft. long, and placed them into a beaker of water. We then tied off the dialysis tubing and poured 25 mL of distilled water in. We repeated this with the rest of the five pieces dialysis tubing, pouring a different molarity of sucrose solution in different dialysis tubes. After all the tubes were filled and tied, we then dried the bags and weigh each one on the scale. After all the data was recorded, we filled all the beakers about ¾ full of distilled water, placed the bags into each beaker in unison, and waited 30 minutes. Next, the bags were removed from the beakers, dried, and weighed separately. We expected the mass to increase with increasing molarity because with the higher the concentrations, more water would need to be diffused into the bag to reach
equilibrium. C. Water Potential
The third part of this lab required that we use five 150 mL beakers of different sucrose concentrations; one of 0.2M, one of 0.4M, one of 0.6M, one of 0.8M, and one of 1.0M, as well as 1 beaker of 150mL distilled water. In each beaker we placed four 3cm potato cylinders. The 3cm potato cylinders were bored from a potato and cut into the appropriate length, separating them into 6 groups of 4. However, before placing the cylinders into the beaker, we weighed each group and wrote the data into a table. Each beaker required only 100mL out of the 150mL and so we used a graduated cylinder to measure the 50mL we did not need and dump it out. After acquiring the right amount of solutions in each beaker we placed one group of 4 potato cylinders in each one. After placing the cylinders we proceeded to cover up each beaker with plastic wrap in order to prevent any substance from changing the outcome of the experiment. The beakers were then left over night in order to observe if any changes were made in the mass of the potato cylinders. The next step of the lab was to weigh the cylinders to observe any changes in mass. We had expected the total mass of the group of 4 cylinders to increase because the water would go into the potato to lower the concentration of sucrose and reach equilibrium.