Protein Diffusion Report

Protein Diffusion Report

Abstract

This experiment was conducted in order to examine whether protein diffuses through a semi-permeable membrane and if it did, at which rate the diffusion occurred. The molecular movement of materials across the cell membrane is a crucial Biological aspect in any individual. There was a Biuret test that was carried out in which a sample, a beaker with water, was all required before experimenting. The set up was all set in which tubing that contained the sample was inserted into the beaker and the contents before and after were then weighed and recorded. The experiment was carried out three times before the average was recorded. The readings were recorded after a quarter of an hour interval. The findings of the experiment were observed. In a case that there was a color change recorded, then there could be protein testing positive. The bag weight did not decrease, and there was no color change, and therefore the Biuret Test conducted proved to test negative. The Biuret test showing positive means that the molecules diffused across the semi-permeable membrane to the beaker and the contents of the bag would therefore reduce. In this experiment, the test proved negative, meaning that the large protein molecules failed to pass through the semi-permeable membrane. The experiment is essential since it used in finding out the presence of peptide bonds.

Introduction

As a student, there are various instances through which one is required to test the presence of protein in food. It is through the availability of peptide bonds that one is in the position to confirm the presence of proteins.  The statement of the question of this study stands out that: Are proteins molecules able to diffuse through a semi-permeable membrane, and what rate do these molecules diffuse? In a situation that the protein molecules diffuse through, then the test will give positive results, and this is through the reagent in the beaker turning to a purple or dark blue. The hypothesis is obtained after an average of three findings from the same period of time is collected and average obtained. If there is no color change, then that means that there was no diffusing of protein molecules across the membrane.  Diffusion is the net movement of materials like molecules, ions, or atoms from a region where they are highly concentrated to a region of lower concentration (Kotysk, 18). The experiments are essential in real life in that the picture of how materials get transported across the cell membrane in bodies is seen (Harrison, 2018). The findings of the experiment should be able to give a clue on how the protein molecules get to move across the cell membrane in living organisms.

Methods

In collecting the experimental data, there are essential techniques employed. Observation is necessary, measuring should also be done to the exact value for the highest level of accurate results, and lastly, the recording needs to be on time to minimize the extent of experimental error obtained. The scientific techniques are essential in getting the correct figures. There are controls when carrying out these methods. Firstly, ensure that the dialysis bag used is of the right quality and is therefore permeable to molecules of less than 500g / mol. A subsample that is used as a control is also obtained for the control experiment. All over the experiment, the CuSO4 solution, the dialysis tube or bag, and the amount of the protein sample used should be kept the constant and same amount of it used in each experiment. Therefore, they are our constants.

Results

In the carrying out of the experiment, the following data was collected.  The data was collected over a period of fifteen-minute a part in three different experiments. The first reading was the onset of it and thus served as a control experiment.

Table 1

Trends in weight changes

The weight of the dialyzing tubing bag increased with the increasing time of the experiment. The figures were collected precisely after the end of every fifteen minutes. As observed, the rate also of the rising weight is seen to have an increasing trend across the divide wit the first fifteen minutes recording the lowest increase whereas the last a quarter an hour recorded the highest figure.

The water in the beaker was observed to reduce in volume with each experiment. The differences in weight, therefore, of the contents in the beaker are observed in the experiment. All through the experiments, there is no color change that is seen.

Table 2: Showing Colour changes observation across the experiments

The beaker contents remained clear as the bag contents remained in its violet state. There was no color change that was also recorded at any particular moment of the experiment.

Discussion

The Biuret test is also referred to as the Piotrowski test. It is an experiment that is normally conducted while trying to test for the presence of proteins in any food test. The test is a chemical test through which the detection of peptide bonds is carried out. The experiment is dependent on Copper ii ions that get supplied from the Copper (ii) Sulphate, which is dropped to the solution. In an experiment where there is a positive test, the nitrogen that is a present element in proteins binds with the blue Copper ii ions to result in a color change. With this experiment, there was no color change that was observed, and therefore, the experiment tested negative.

As stated, diffusion involves the movement of molecules down the concentration gradient across a cell membrane. In this experiment, the study was to find out if the large protein molecules get to pass easily through membranes. The 6 centimeters dialysis tube acted as the artificial membrane. Since the concentrations of the proteins were much inside the tube than the beaker, the expected results were that the molecules would flow from their region of high concentration to the region of lower concentration, by the experiment proving negative means that the molecules were unable to move across the gradient. The increase of the weight of the bag meant that the water molecules passed from their region of high concentration to their area of lower concentration. The movement of the water across the dialysis tube means that the tube allowed a selective movement of the materials across it.

The dialysis tube acts the same way through which our cell membrane functions (Herbst & Market, 17). The characteristic depicted through this behavior is termed as the selective permeability of the cell membrane. Organisms depend on the movement of materials for their survival. Water molecules get to move across the cell membrane through a process of osmosis to meet the metabolic needs of the organism. The beaker in this scenario is a hypotonic solution, whereas the dialysis bag is hypertonic. Normally the molecules of water actively move from a hypotonic solution to that of a hypertonic solution. The organisms are set in a way that another version through which large molecules like the amino acids get to be transported across the cell membrane. A carrier is introduced and actively moves the large molecules across the cell membrane. Passive transport does not require any energy to move these molecules, but with the active transport, there has to be an ATP producing source. Biological systems depend on these movements for their survival.

Lastly, there needs to be keenness in the material choice to avoid inaccurate results. The 10% protein substance needs also to be used. The concentration of the copper ii sulphate solution Also needs to be used with only two drops dropped. The test comes with fewer limitations too. This particular test cannot be used even in a positive experiment to know the number of available proteins. It is just used to confirm whether there is the availability of the peptide bonds or not. In the future, there should be a known standard sample through which an approximation of the amount can be easily be made.

References

Harrison, E. (2018). Role-Playing Activity to Demonstrate Diffusion Across a Cell Membrane. Journal of microbiology & biology education, 19(2).

Herbst, W. A., & Martin, K. C. (2017). Regulated transport of signaling proteins from synapse to nucleus. Current opinion in neurobiology, 45, 78-84.

Kotyk, A. (2018). Basic Kinetics of Membrane Transport. In Structure and Properties of Cell Membrane Structure and Properties of Cell Membranes (pp. 1-9). CRC Press.