Osmosis and it’s Function
Observation of Eggs Reaction to Glucose Solutions and Distilled Water
Osmosis in Action
Osmosis is a process of passive transport that causes randomly moving H20 (water) molecules to travel across a semi-permeable membrane against the concentration gradient. Osmosis depends on the concentration of the solutes in a solution. The direction of water movement is from the hypotonic to hypertonic in order to maintain equilibrium: a homeostasis inside and out. The act of going over a selectively permeable membrane takes up little to no effort and this is called passive transport. Contained in eggs are clusters of sugars, proteins, and other polar molecules trapped inside of the membrane. Outside the eggs are solutions made up of a solvent varying in concentrations of dissolved glucose. It is important that the driving force of the solutions inside and the outside the egg remain equal in the isotonic state. In this state water is constantly moving in and out of the egg at an equal rate.
The eggs were prepared by soaking them in vinegar for 48-72 hours. The acid will decalcify the shell while keeping the soft semi-permeable membrane that incases the egg white and yolk intact.
The materials and methods used in preforming the osmosis lab are contained in the CCBC-Biology 108 Lab Manual (Kilbourne, & Montgomery, 2007). There were no modifications or exceptions to the lab procedures.
Graph 1-Mass of eggs soaked in various solutions over time
The mass of the eggs in DW (distilled water) was observed to fluctuate over time.
The mass of the eggs soaked in 0.5 M, 1.0 M, 1.5 M, and 2.0 M glucose solutions were observed to decline in mass, with the 1.5 M solution decreasing the most at 90 mins with an ending mass of 79.2. The most isotonic of all of the solutions was the 0.5 M glucose solution.
Graph 2- percent change in mass of eggs in various solutions over time
The percent of change in the mass of the egg soaked in distilled water was observed to increase at a steady rate.
The percentage rate in the 0.5 M, 1.0 M, 1.5 M, and 2.0 M glucose solutions were observed to decrease more rapidly the higher the solution concentration. The 0.5 is shown to be isotonic.
If a concentration is isotonic then fluids inside and outside of the egg are equal it provides an equilibrium and provides for proper functionality for many living organisms. Distilled water serves as a control in this osmosis experiment. Water moves steadily in and out of the egg to maintain balance, which is reflected in the lab results.
Question 1: Distilled water (isotonic), was the control solvent and because there was an equilibrium of the solutes (glucose) inside and out, there was constant water movement. You would expect water to try to dilute the egg, as inside all the proteins are contained.
Question 1: 0.5 M glucose (decreased slowly – hypertonic) The concentration of solutes (glucose) was greater on the outside than the inside of the egg, so water had to exit the egg in order to obtain equilibrium. This concentration of solutes was the closest to being isotonic.
Question 1: 1.0 M glucose (decreased more quickly – hypertonic). This concentration of solutes (glucose) was greater on the outside than the inside of the egg, compared to the 0.5 M glucose, so water had to exit the egg in order to obtain equilibrium.
Question 1: 1.5 M glucose (decreased faster – hypertonic). This concentration of solutes (glucose) was greater on the outside than the inside of the egg, compared to the 0.5 M and the
1.0 M glucose, so water had to exit the egg in order to obtain equilibrium.
Question 1: 2.0 M glucose (decreased fastest – hypertonic). This concentration of solutes (glucose) was greater on the outside than the inside of the egg, compared to the 0.5 M, the 1.0 M and the 1.5 M glucose, so water had to exit the egg in order to obtain equilibrium. As the concentration of solutes (glucose in the surrounding solution) increased, it was necessary for the water to exit at a quicker rate in order to obtain equilibrium.
Question 2: The distilled water contained no glucose and was isotonic. All the glucose solutions were hypertonic.
Isotonic means that the osmotic concentration on the inside and outside of the egg are equal, but water is constantly moving in and out at a steady rate.
Hypertonic means that the osmotic concentration outside the egg is greater than that inside of the egg. Water must diffuse from the egg to the outside solution for equilibrium to occur, thus causing the egg to lose weight.
Hypotonic means that the osmotic concentration outside the egg is less than that inside of the egg. Water must diffuse into the egg for equilibrium to be reached, thus causing the egg to increase in weigh.
Question 3: A situation in everyday life that illustrates the concept of osmosis is kidney dialysis. The dialysis tubing (cartridge) provides a semi-permeable membrane between the blood and the dialysis solution. Dialysis serves as the filtering function of the kidneys by removing toxins such as metabolites and extra electrolytes from the blood.
Question 4: Oral Rehydration Therapy is used to rehydrate a person who has become dehydrated due to diarrhea, which is extremely common in third world countries. In this situation an increased amount of water needs to be ingested, but in this state the body cannot actively absorb the water quickly. Osmosis comes into play with the use of a solution composed of water, sodium, and glucose (electrolytes). The sodium is quickly absorbed by the cells due to the lower concentration caused by dehydration; and the sodium attracts the glucose which is also absorbed by the cells, called co-transport. The glucose concentration is hypotonic causing more water to enter into the cells which promotes quick rehydration. This is both a cheap and highly effective method of rehydrating individuals.
Question 5: In terms of osmosis, this explains what happens to a patient’s blood when they are mistakenly hooked up to an IV bag of strictly distilled water as opposed to a salt-buffered IV solution. The use of only distilled water would cause the interior of the blood cell to have a higher solute concentration, placing them in a hypotonic situation. This larger concentration gradient creates osmotic pressure which causes the red blood cells to swell and eventually burst.
Question 6: There are many areas of the world that use reverse osmosis to desalinate water to make it potable, but the two largest areas include the Middle East and the United States. In particular, Israel and California produce the most water using this process. These areas get much of their water from the ground, rain water, and imports. Due to the high demand, shortages, and drought, reverse osmosis desalination plants have become prominent in the production of high-quality drinking water using ocean water. The refinement of the polymer membrane used to filter out the salt ions from the ocean water in the reverse osmosis desalination process has promoted a better and more efficient system. This has aided in stabilizing water prices and in some cases, price reductions. Based on research performed to date, there has been no findings of any type of long-term impact to the environment.
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