Name: Hour: Biology Biology Unit 2-Biomolecule Identification Lab

Transcription

1 Name: Hour: Biology Biology Unit 2-Biomolecule Identification Lab Objectives: - Apply knowledge of biomolecule reagents to identify types of biomolecules. - Identify the type of biomolecule present per unknown sample. - Identify the chemical function of each biomolecule per unknown sample. Background: Reagents are chemicals that we will be using in this lab to identify different types of biomolecules. Recall that there are 4 types of biomolecules: carbohydrates, lipids, proteins and nucleic acids. In this lab we will be conducting two different tests for carbohydrates, a test for lipids and a test for proteins. You will be provided 5 unknown samples, each containing one type of biomolecule. You will be reacting the chemicals with each unknown sample to thereby identify the biomolecule present, and the given cellular function of each sample. To test carbohydrates we will be using Benedict s Solution and Iodine. Benedict s solution is used to test for the presence of monosaccharides. Benedict s solution is naturally a light, clear blue colored solution. If the Benedict s Solution turns the sample an opaque yellow/orange color, this shows the positive presence of monosaccharides. Iodine is used to test for the presence of polysaccharides. Iodine is naturally a dark amber (or yellow-brown) color. However, if the iodine turns the sample a very dark black-purple color, this shows the positive presence of polysaccharides. When testing for lipids, we will combine samples with Sudan IV powder. Sudan IV powder only binds with lipid molecules. If Sudan IV powder is mixed with a solution not containing lipids, it will simply separate out and float on the surface like dust or debri. If the powder is mixed with a solution containing lipids, you can expect to see it stain the entire solution a deep red color. Lastly we will test for the presence of proteins using Biuret Solution. Biuret in its natural state is a light pink/red color. However, when mixed with a solution containing protein, it will change the color to a light violet or lilac color. Your job is to conduct an experiment per unknown sample, in order to identify the present biomolecule. You and your group will then collect your observed data, and report out to the class with your findings.

2 Hypotheses: All hypotheses should be in the If, then. -format. A hypothesis is not a random guess you pull out of thin air, but should be a logical and educated prediction, using known scientific concepts. For the following write out a hypothesis for each reagent test: (1) For the Benedict s Test: If, then. (2) For the Iodine Test: If, then. (3) For the Sudan IV Test: If, then. (4) For the Biuret Test: If, then. Reagent Results (Quick Review) Reagent Positive Test Negative Test Benedict s Iodine Sudan IV Biuret

3 Experiment Directions: - You will be working in groups of 3. - Each group will be assigned only one type of reagent test. - Once your assigned test is completed, record your data and sit down. - The class as a whole then will compile their collected data. Benedict s Test Directions: 1- Place ½ pipette of each unknown sample into its own individual test tube. (Make sure the labels correspond correctly. *Use test tube rack.) 2- Mix ½ a pipette of Benedict s Solution into each unknown sample test tube. (*Use test tube rack.) 3- Carefully place each test tube into the hot water bath. 4- Allow test tubes to sit in the water for 5-10minutes (until a color change is observed). 5- Carefully take the test tubes out of the hot water bath using test tube tongs, and place back in test tube rack. 6- Record observations in Benedict s Test Data Collection. 7- Sit and begin working on your section s analysis and conclusion until the class is ready to progress. Iodine Test Directions: 1- Place ½ pipette of each unknown sample into its own individual test tube. (Make sure the labels correspond correctly. *Use test tube rack.) 2- Mix ½ a pipette of Iodine Solution into each unknown sample test tube. (*Use test tube rack.) 3- Carefully mix each solution by flicking the base of the test tube. 4- Record observations in Iodine Test Data Collection. 5- Sit and begin working on your section s analysis and conclusion until the class is ready to progress. Sudan IV Test Directions: 1- Place ½ pipette of each unknown sample into its own individual test tube. (Make sure the labels correspond correctly. *Use test tube rack.) 2- Use the toothpick to drop a small amount of Sudan IV powder into each unknown sample test tube. (*Use test tube rack.) 3- Carefully mix each solution by flicking the base of the test tube. 4- Record observations in Sudan IV Test Data Collection. 5- Sit and begin working on your section s analysis and conclusion until the class is ready to progress. Biuret Test Directions: 1- Place ½ pipette of each unknown sample into its own individual test tube. (Make sure labels correspond correctly. *Use test tube rack.) 2- Mix 5-10 drops of Biuret Solution into each unknown sample test tube. (However many drops you choose, make sure it is consistent between test tubes.) 3- Carefully mix each solution by flicking t base of the test tube. 4- Record observations in Biuret Test Data Collection. 5- Sit and begin working on your section s analysis and conclusion until the class is ready to progress.

4 Data Collection Sample Water (Control) Sample Water (Control) Sample Water (Control) Sample Water (Control) Benedict s Test Observations Iodine Test Observations Sudan IV Test Observations Biuret Test Observations Positive / Negative Test Positive / Negative Test Positive / Negative Test Positive / Negative Test

5 Analysis & Conclusion (1) What was the purpose of running the reagent tests on the distilled water? (2) For each solution identify which biomolecule was present, and how you know this: Biomolecule Present How Do You Know This? Sample #1 Sample #2 Sample #3 Sample #4 Sample #5 (3) Connect the Samples to their Monomers and Polymers: Question glucose or fructose? Which same could contain fatty acids? nucleotides? disaccharides? polysaccharides? polypeptides? glycerol? amino acids? monosaccharides? Sample # How do You Know This?

6 (4) Connect the Samples to their Biomolecule Question Which sample could provide your cells with immediate energy? Which sample could your cells use to store long term energy? Which sample would probably provide your cells more with intermediate energy (rather than immediate)? Which sample might be able to catalyze chemical reactions inside your cells? Which sample could possibly form the cell membranes? Which sample is the expression of DNA/RNA? Sample # How do You Know This?

7 (5) You are given another scientist s biomolecule data. Analyze their data table and draw conclusions. Reaction with Biuret Reaction with Benedict s Reaction with Sudan IV Reaction with Iodine Water Sample-X Sample-Y Sample-Z Sample-A Sample-B A- Looking at the data for Sample-X, provide all of the details you can conclude about B- Looking at the data for Sample-Y, provide all of the details you can conclude about C- Looking at the data for Sample-Z, provide all of the details you can conclude about

8 D- Looking at the data for Sample-A, provide all of the details you can conclude about E- Looking at the data for Sample-B, provide all of the details you can conclude about