Diffusion Water Lab

Certain substances are able to diffuse across plasma membranes under the right conditions through selective permeability. The selection of these certain substances allows for cells to maintain homeostasis, as these substances move from higher concentration to lower concentration. The purpose of this experiment is to see whether or not Lugol’s will be able to diffuse across dialysis tubing, which acts as a membrane. Lugol’s turns black when it interacts with starch, which will make the diffusion easy to see. This is all based off of a caterpillar eating a plant. The starch present in the leaves causes the caterpillar to produce amylase, which breaks down starch. In one experiment, the tubing will contain starch and amylase, while the other tubing

6. What results would you expect if the experiment started with glucose and Lugol’s Solution

In the rubber egg lab also known as the osmosis lab, I first measured the circumference of the egg which was 6 inches. The egg had no cracks and was hard. I placed the egg in the vinegar and within seconds the egg started to bubble. These bubbles were carbon dioxide. After 72 hours the shell of the egg had started to dissolve or flake. This would be considered passive transport as the vinegar diffused across the egg shell without any force. Seventy-two hours into the experiment the membrane was exposed, and had a circumference of 8 inches. Before the egg had a shell and you couldn’t see through it but once the vinegar acted as an acetic acid it broke down the shell and left a yellow membrane that felt like rubber this is an example of diffusion. I then placed the egg in another container and put corn syrup over the egg for 24 hours. The egg had shriveled and shrunk, the water had left the egg and went into the syrup and that is what caused the egg to shrink. The corn syrup is essentially pure sugar with very little water so the osmotic pressure is very low. I then placed the shriveled egg in water and waited for another 24 hours. After observation the egg had no

If the solution in the left beaker contained both urea and albumin, which membrane(s) could you choose to selectively remove the urea from the solution in the left beaker? How would you carry out this experiment?

In this lab experiment, half our group observed and measured osmosis using dialysis tubes that were represented as the semipermeable membrane. It is permeable to water and other small molecules but is impermeable to larger molecules such as the sucrose solution used in each of the four beakers and tubing. The other half of our group observed the tonicity of sheep blood to determine whether the blood was isotonic, hypotonic, or hypertonic. The 85 g/dL of NaCl solution was the ideal isotonic number in relation to the sheep blood cells as well as a reference to the other observations of the solutions.

The purpose of these experiments is to examine the driving force behind the movement of substances across a selective or semiperpeable plasma membrane. Experiment simulations examine substances that move passively through a semipermeable membrane, and those that require active transport. Those that move passively through the membrane will do so in these simulations by facilitated diffusion and filtration. The plasma membrane’s structure is composed in such a way that it can discriminate as to which substances can pass into the cell. This enables nutrients to enter the cell, while keeping unwanted substances out. Active

The independent variable was the concentration of sucrose in the dialysis tubing we used as a simulated membrane.

Dialysis tubing is a membrane made of regenerated cellulose fibers formed into a flat tube. If two solutions containing dissolved substances of different molecular weights are separated by this membrane, some substances may readily pass through the pores of the membrane, but others may be excluded.

Table 1 shows the contents of the bags and the content of the concentration it was submersed in. Bags 2-4 each contain a solution of both sucrose and water. These bags were each put into beakers containing hypertonic solution. These bags gained weight over time because the water moved from its high concentration inside the beaker to the low concentration inside the membrane of the artificial cell, the membrane being the bags that consisted of dialysis tubing. The

In this experiment, we will investigate the effect of solute concentration on osmosis. A semi‐permeable membrane (dialysis tubing) and sucrose will create an osmotic environment similar to that of a cell. Using different concentrations of sucrose (which is unable to cross the membrane) will allow us to examine the net movement of water across the membrane.

The difference is that along with large molecules, living cells prevent molecules with positive charges and solubility. This is not representing in dialysis tubing, and is only found in living cells because the tubing is only based on molecular size (98). When referring the rate of diffusion, the concentration gradient influences the diffusion rate, based on the factors of temperature. The ability for molecules diffuse from high to low concentrations primarily depends on the concentration gradient between the two areas.(96-99). My hypothesis for the study is that in the hypotonic, hypertonic, and isotonic solutions, the direction and rate of osmosis will determine based on the concentration inside the dialysis tubing. My prediction is that if the solution is hypotonic the results will decrease, if the solution is hypertonic the results will increase and if the solution is isotonic the solution will vary and or remain constant.

The objective of this lab was to build a selectively permeable membrane and observe osmosis and diffusion through this membrane. There were four cells created; starch, starch and amylase, salt and glucose. For testing if starch was apparent a few drops of iodine where placed in each cell. For all of the cells starch was not apparent this is because starch molecules are too large to pass through the cell

Lab Conclusion So was the data right, or wrong? Our class did two labs. One of the labs was a diffusion lab to prove the concept in its entirety, and the second lab was over a “naked” egg and how it changed in shape. We can say that all of the changes present in each lab was due to diffusion.

The question that is being asked in this lab is what happens when the egg is put in an acid bath, water bath, then a corn syrup bath. In the acid bath the egg will do something to the shell. The hypothesis that was created for the acid bath is that if the egg is put in the acid bath then the acid will destroy the cell because the acid will eat away at the calcium of the shell. The hypothesis that was created for the water bath then the egg will increase in mass because the water starts to fill the egg. The hypothesis that was created for the cron syp bath is that if the egg is placed in the corn syrup bath the egg will weigh less because the water will leave the egg and corn syrup eats away ah the egg. The

In the final experiment we filled a dialysis bag with starch solution and tied off both ends of the bag so that it is water tight. We then filled a separate bag with sodium chloride and submerge both dialysis bags in two beakers of distilled water. We allowed the bags to sit in the water for 10 minutes. We then put silver nitrate into the water that held the dialysis bag filled with sodium chloride and recorded any changes in the water. We then added iodine to the water that held the dialysis bag of starch and observed any changes in the water.