- Information
- AI Chat
Osmosis Full Lab Report
Foundations of Biological Sciences I (BIO SCI 150)
University of Wisconsin-Milwaukee
Preview text
CING KIIM
Lab-3: Osmosis
INTRODUCTION: Small molecules, such as water, can enter and exit the cell through spaces between membrane molecules by diffusion. Diffusion is the process of random movement toward a state of equilibrium. However, the cell membrane represents a barrier to substances which are either charged or larger in size. Membranes that block or otherwise slow passage of certain substances are said to be selectively permeable. Osmosis is the diffusion of water across the membranes. The process depends on the relative concentration of water molecules on both sides of the membrane.
Tonicity describes one solution’s solute concentration to that of another solution. A hypotonic solution has a lower solute concentration than the other solution. Isotonic solutions have equal solute concentrations. A hypertonic solution has a higher solute concentration than the other solution. Plant cells will shrink and pulls away from the cell wall if they are placed in hypertonic solution on the outside. The process is known as plasmolysis. In animal cells, the cells will lose water, shrivel and have spiny appearance when they are placed in hypertonic on the outside. Plant cells will stiffen if they are placed in hypotonic solution on the outside. They generally retain their shape due to the presence of cell walls. However, animal cells will swell and burst if they are placed in solution hypotonic on the outside.
Hypothesis: Water molecules will move from lower solute concentration to higher solute concentration.
Prediction: If water molecules move from lower solute concentration, then water will move into the dialysis tubing in bag 2 and 3 which have higher solute concentration inside the bag. Water will move out of bag 3 since it has higher solute concentration outside the bag. The weight of bag1 will remain the same since the bag is placed in isotonic solution.
In this experiment, the dependent variable is the change in the weight of the dialysis tubing bags. Contents of dialysis tubing bags and contents of beakers are the independent variables.
METHODS: For the experiment, we needed four 15-cm sections of dialysis tubing presoaked in reverse osmosis water (RO H 2 O), 8 pieces of rubber bands, 4 labels, a funnel, four 400-mL beakers, graduated cylinder to measure 10mL, paper towels, balance with weight boats, RO H 2 O, 15% sucrose solution, 30% sucrose solution, and scissors.
We obtained four 15-cm long sections of dialysis tubing that had been presoaked water and created bags by folding over one end of each dialysis tube and tied the end with a rubber band. We also obtained four beakers, labeled the beakers, and added 200mL RO H 2 O to beaker 1, 2, 3 respectively. We also added 200mL 30% sucrose solution to beaker 4. With the help of a funnel and a graduated cylinder, we filled 10mL of RO H 2 O,10mL of 15% sucrose solution,10 mL 30% sucrose solution, 10mL of RO H 2 O to bag 1,2,3, and 4 respectively. After filling the bags with the solutions, we smoothed out the top of the bags to remove excess air and then we folded and
tied the other end of the bags. We then rinsed each bag with RO H 2 O and dried the bags using paper towels. With the help of a weight boat, we recorded the weight of each bag at time=0 min. Then we placed bag1,2,3, and 4 into beaker 1,2,3, and 4 respectively. After 15 mins, we took out each bag from its beaker, dried the bag, weighed and recorded the weight in Table1. The step was repeated after 30, 45, and 60 minutes.
RESULTS: Bag# Contents of bag
Contents of beaker
Bag weight at 0 min(g)
Bag weight at 15mins(g)
Bag weight at 30mins(g)
Bag weight at 45mins(g )
Bag weight at 60mins(g ) 1 RO H 2 O RO H 2 O 7 7 7 7 7. 2 15% sucrose
RO H 2 O 10 11 11 12 12.
3 30%
sucrose
RO H 2 O 7 8 8 9 9.
4 RO H 2 O 30%
sucrose
10 9 8 8 7.
Table1: Change in weight of Dialysis Tubing Bags due to Osmosis From Table1, it is observed that the weight of bag 1 and 4 decrease by 0 g and 2 respectively whereas the weight of bag 2 and bag 3 increase by 1 g and 2 respectively after 60 minutes.
DISCUSSIONS: The data collected in the experiment supported our hypothesis for bag2,3, and 4. The weight of bag 2 and 3 increase after 60 minutes as we expected. It implies that water molecules diffuse into the bag through the dialysis tubing bag since the solute concentration is higher in the inside. In bag 4, the water molecules diffuse into the solution through the dialysis tubing bag since the solute concentration is higher on the outside. However, the data collected did not support our hypothesis for bag 1. Since the contents inside and outside the dialysis tubing bag are the same in bag 1, the net movement of water should have been zero. However, from our experiment, there was a slight decrease in the weight by 0. I assume that there was an error in handling the tubes while filling the bag with RO H 2 O.
CONCLUSION: The overall purpose of this experiment was to study the osmosis and observe the osmosis in isotonic, hypotonic, and hypertonic solutions using dialysis membrane (a selectively permeable membrane) which is a thin sheet of cellulose and mimic the properties of plasma membrane in living cells. From the above experiment, I learned that osmosis is required for the cells to remain hydrated and to keep optimum concentration of the cells inside living organisms.
REFERENCES: Biology Lab Manual
Osmosis Full Lab Report
Course: Foundations of Biological Sciences I (BIO SCI 150)
University: University of Wisconsin-Milwaukee
