BIOL 140 Lab—The Chemical Composition of Cells Name ____________________________ I) Introduction All cells contain four major types of macromolecules: carbohydrates, lipids, nucleic acids, and proteins. In today’s lab, we will be studying three of the four-proteins, carbohydrates and lipids. Various chemical tests can be used to detect the presence of each of these molecules. Most of the tests involve a color change visible to the eye. If a color change is observed, the test is considered positive. If the color change is not observed, the test is negative, indicating that a particular molecule is not present. In all the chemical tests we will be performing, we will also be using a control. In most cases, the control will be a sample of …show more content…
d. Add one drop of I2KI solution to each of the wells and record your result in the table below. Table 2. Iodine Test Results Spot water glucose sucrose starch onion slice potato slice Color positive or negative? e. Please answer the following questions about your results: 1. Did you expect water to turn blue-black in the presence of IKI? Why did we test it? 2. What general statement can you make about the differences between carbohydrate storage in onions compared to potatoes? 3. Why didn’t glucose give a positive result? B) Proteins Proteins are made up of chains of amino acids. Each protein folds into a characteristic three dimensional shape that is essential to its function. They perform a variety of functions in cells and are probably the most diverse macromolecule in living systems. The Biuret test detects the presence of proteins and short peptides (short chains of amino acids). Biuret reagent contains a strong solution of sodium hydroxide (NaOH) and a very small amount of dilute copper sulfate solution. The reagent changes color in the presence of a protein because the amino groups in the amino acids react with the copper ions producing a violet color. A negative result is blue. 1. Number four clean test tubes 1-4. 2. Place 1 ml (or 20 drops) of the following solutions into each tube: water, egg albumin, starch, and chicken broth. 3. Add 3 drops of Buiret reagent to each tube and gently shake
The protein molecules in many foods provide the amino acid building blocks required by our own cells to produce new proteins. To determine whether a sample contains protein, a reagent called Biuret solution is used. Biuret solution contains copper ions. However, the chemical state of the copper ions in Biuret solution causes them to form a chemical complex with the peptide bonds between amino acids (when present), changing the color of the solution. Biuret solution is normally blue, but changes to pink when short peptides are present and to violet when long polypeptides are present.
The purpose of this lab was to test different substances using various procedures to see what biomolecules were present and ultimately find out what restaurant Anna Lyza had eaten at before she died. For the first control test, we used vegetable oil to test for lipids. So, if the solution does not contain lipids, it does not become translucent when placed onto a paper bag square and held up to a light. So, it is a negative result. However, in the presence of lipids, the solution will become translucent when placed onto a paper bag square and held up to a light. Therefore in this case, the result is positive. On the other hand, we used albumin egg to test for proteins in another control test. If the solution does not contain proteins, it will not experience any color change and so it is a negative result. When there are proteins existing in the solution, it will turn bluish/purplish and for this reason it is a positive result. Furthermore in the third control test, we used dextrose to test for simple carbohydrates such as glucose. If the solution does not contain simple carbohydrates, it will not undergo any color change and will remain a blue color. So, it is a negative result in this circumstance. If there are simple carbohydrates present in the solution, the solution will turn reddish and so the result is positive. For the last control test, we used starch solution to test
All living things contain some form of organic macromolecules including: Lipids, proteins, carbohydrates and nucleic acids. All of these organic molecules are alike in the sense that is they are made up of bonded elements such as carbon, hydrogen, oxygen, and to smaller quantities nitrogen, phosphorus and sulfur. The macromolecules each contain large long chains of carbon and hydrogen atoms and often consists of repeating smaller molecules bonded together in a repeating pattern (polymers). To test whether a specific solid white substance is a protein is simple due to the unique chains found in the respective type of macromolecule. To test if the substance is a carbohydrate, two tests could be performed on separate samples of the object. First,
In doing the lab, one was able to determine the characteristics of the given solutions, containing different macromolecules, whilst doing the multiple tests. The tests performed were,
Colorimetric assay is a process of determining a concentration of a solution based on absorbance of light. The purpose of this lab is to determine if the Bradford assay is an accurate way to determine an unknown concentration of two samples of protein. The Bradford assay is done by measuring wavelength of light passing through a cuvette filled with Bradford dye and concentrations of PBS and proteins. After the cuvettes are mixed they are placed into a spectrophotometer to measure wavelength. The wavelength given will be used to plot a standard curve based on concentration (x-axis) and wavelength (y-axis). The standard curve is then used to measure an educated guess on the concentrations of unknown protein concentrations. We hypothesized that if we use the Bradford assay and colorimetric spectrophotometry we can determine an accurate concentration of two unknown concentrations of proteins. The results of this lab failed to reject our hypothesis based on accurate measurements of protein concentrations. The standard curves are drawn with a linear increasing slope. The Bradford assay is an accurate way to demine the concentration of an unknown concentration.
A cell, the building block of all living organisms, is composed of four fundamental biomolecules: proteins, carbohydrates, sugars and lipids. Proteins provide a vast amount of functions cells such as they serve as enzymes, provide structural support to cells, and act as antibodies. Reagents are used to spark a chemical reaction. The reagent used to detect protein traces in a substance is Biuret’s. Biuret’s will turn purple if proteins are present and blue if they are none. Biuret’s copper particles, have a charge of +2, are diminished to a charge of +1 when peptide bonds, which are in proteins, are present, creating the color change. Polysaccharides, which are carbohydrates, are most notably known to provide energy to the body, but they also help in breaking down fatty acids. Iodine is the reagent used to determine whether a substance has starch in it. The iodine/starch complex has energy levels that are only for retaining unmistakable light, giving the complex its extraordinarily dark black-blue shade. If there is no starch found, iodine will remain its natural yellowish-brownish color, but if starch is present, iodine will turn blue-black. Monosaccharides, which are sugars, like polysaccharides, provide the body with energy. To detect monosaccharides, the reagent, Benedict’s, is used. Benedict’s reagent is added to a test tube, then it is placed in
4. Describe the test used to detect the presence of each type of biologically important
b) Benedict test the solution color will change from blue to pink/orange red, indicating simple sugars are present. Lugols test the solution color will change from yellowish brown to dark purple, indicating starch and polysaccharides are present. Sudan iV test the lipid content will turn into red, indicating lipids are
4.Measure 35mL of warm water and add them into each of the 4 test tubes at about roughly the same time. It is essential that the water is warm. Do not seal the test tube.
1 ml of water should be added to the first test tube and make a note. In the second test tube, 1 ml of methyl alcohol should be added. In the third test tube, 1 ml of hexane must be added. Lastly, the fourth test tube will be a control.
Proteins are one of the main macromolecules that are important for human function. This study examines the presence of proteins in the given samples. The Biuret reagent created a color transitioned on the various samples. The Biuret reagent is an aqueous solution that is composed of sodium hydroxide and copper (II) sulfate. The copper ions in the Biuret reagent react with the peptide bonds which cause the color change in the test samples. The amount of protein in the various samples determined the color transition. The sample solutions with lower presence of protein did not change color as opposed to the sample solutions with a higher presence of
After the hour has passed, remove the tubes and add 2-3 drops of biuret reagent to each tube and shake.
Step 1 and 2 was repeated by using distilled water by replacing the test solution.
Half of each tube’s contents are poured into a new test tube each respectively after the tubes are incubated for 1 hour. One set of tubes is tested for:
There are multiple methodologies implemented by scientists to determine protein concentration. One of the oldest and most commonly used methods is the Biuret method (Okutucu and others 2007). The Biuret method is a colormetric assay that utilizes a spectrophotometric change accomplished by reactions containing peptide bonds in conjunction with copper (Okutucu and others 2007; Gornall and others 1949) to determine protein concentration based on a standard reference.