Week 3 Ch 3 Lab 4 Chem Comp of Cells

sNote: All your answers to questions must be in Red or other color (not including blue) for easier grading. Points will be deducted if you do not distinguish your answers. Lab 4. Chemical Composition of Cells Objectives:  Describe the properties of some important biomolecules.  Explain important characteristics of proteins and carbohydrates.  Perform tests to detect the presence of carbohydrates and proteins.  Explain the importance of a control in biochemical tests.  Use a biochemical test to identify the presence of a molecule in an unknown solution. Vocabulary:  Carbohydrates  Proteins  Lipids  Nucleic acids  Peptide bond Introduction: The cells of living organisms are composed of large molecules (macromolecules) sometimes also referred to as organic molecules because of the presence of the element carbon. Very many of the organic molecules found in living organisms are carbohydrates, proteins, lipids , and nucleic acids . Humans are omnivores in that they consume a variety of food types from several different ecosystem levels. The biomolecules we consume provide us with energy and building blocks for our bodies to function. Vitamins and minerals are important dietary components required in small amounts. Water is not a nutrient or a source of calories but is critical to life. Today, we will focus on three of these molecular types: lipids, proteins, and carbohydrates. Part 1: Testing for Simple Sugars Background Information: Carbohydrates include sugars and starches and are composed of monosaccharide building blocks. Glucose is a simple sugar, a monosaccharide. Fructose is a monosaccharide found in honey, tree fruits, berries, and many vegetables. It is the sweetest naturally occurring sugar. Two simple sugars joined together form a disaccharide. An example of a disaccharide is sucrose (table sugar) which is formed by glucose + fructose. Lactose, also known as milk sugar, is a disaccharide composed of a galactose and

a glucose molecule. The enzyme lactase is required to break down lactose into its two monosaccharide sugars. Lactase is normally secreted by intestinal cells. In many people, the production of lactase diminishes with age, and they become lactose intolerant. Starches are polysaccharides which contain many linked sugar molecules. Benedict’s reagent is the indicator we use to detect monosaccharides. When monosaccharides are mixed with Benedict’s and heated, a color change occurs. Benedict's reagent is blue, but when heated in the presence of a reducing sugar, changes color. Green, yellow (+sugar), orange (++ sugar), or red (+++ sugar). In the following experiment you will test different solutions to see how much monosaccharides are present, if any. Question: What common household items contain more monosaccharides? Hypothesis: Hypothesize what will be the color change (Green, yellow, etc.), if any, for each solution. Record your prediction in Table 1 below. Materials:  Benedict Solution  Distilled Water  Glucose Solution  Starch Solution  Soda  Milk  Sugar Free Energy Drink  70°C Water bath  6 Test tubes  Test tube rack  7(5 mL) Serological Pipets and pumps  Wax Pencil  Timer  Paper and pencil  Hot hands Procedure: 1. Make sure your water bath is heating. 2. Label tubes. Use a wax pencil to label the tubes with the test tube 1-6. 3. Add 2 mL of corresponding solution to each test tube. Be sure to add the solutions based on the test tube number listed on the table below. 4. Add 2 mL of Benedict’s solution to each test tube and swirl to mix. Record the color in Table 1 below.

sugars. Positive result. 6 “Sugar- Free” Energy Drink Yellow Blue Green The color varied; it contains reducing sugars. Positive result. Conclusion: 1. What are the monomers that make up carbohydrates? Monosaccharides aka easy sugars like glucose and fructose are building blocks that make up carbohydrates. 2. Which test tube was your negative control? Which was your positive control? Explain your answer. Test tube one (distilled water) because it is not a nutrient or a source of calories... it has no reducing sugars, so it is the negative control. The test tube(s) that has a known outcome is the positive control, which is test tube two (glucose) and test tube five (milk) because they have reduced sugars. 3. The volume of Benedict's reagent added to each tube is a controlled variable. Identify 3 additional controlled variables. The other three controlled variables are the volume of the solutions being tested, the water bath time of three minutes, and the measurement of the amount of iodine. 4. The dependent variable changes in response to the experimental variable and is used to assess the experimental outcome. Identify the dependent variable. In the Benedict’s test, the variable is the reagent because it is the indicator used to detect monosaccharides. When monosaccharides are mixed with the Benedict’s solution and heated, the color will transform but will also vary in shade. 5. Do your results support your hypothesis? Explain. A little of both yes and no. To me, it was obvious that distilled water and the starch solution would turn to blue, since the solution (is already blue) acts like a dye which would turn the liquid to blue too. For the glucose, soda, milk,

and the sugar free energy drink, those I just took a guess based on what I imagine the color reaction would be thinking they all contain sugar, but I wasn’t sure by how much it would affect its transformation color. Part 2: Testing for Lipids Background Information: Lipids are a class of molecules that are not soluble (do not dissolve) in water. They are composed of molecular building blocks of glycerol and three fatty acids. Fatty acids come in two major types, saturated and unsaturated. This difference is due to the presence of particular types of bonds within the fatty acid molecule and affects the shape and characteristics of the overall lipid containing these fatty acids. Today we will be performing the Paper Test to identify the presences of lipids. The paper turns translucent (gets a grease spot) in presence of lipids. Question: Which sample solution will contain lipids? Hypothesis: Hypothesize what will be which solution will have lipids present in the sample (no lipids, some lipids, etc), if any, for each solution. Record your prediction in Table 2 below. Materials:  Distilled water  Vegetable oil  Hand cream diluted in water  Shampoo diluted in water  Brown paper bag  4 Disposable pipets  Timer  Paper and Pencil Procedure: 1. Draw four circles in a brown paper bag and label them: Water, Oil, Cream, and Shampoo. 2. Put two drops of each corresponding substance on a brown paper bag. 3. Put the bag off to the side and let it sit for 15 minutes. 4. Record the appearance of the bag where you placed the spots in Table 2. Results: (Watch the Lab 4. Chemical Composition of Cells video) Table 2: Results for Testing for Lipids Sample Hypothesis Appearance After Drying Conclusion

Background Information: Proteins are polymers of amino acids. Amino acids are small molecules that contain an amine (-NH 2 ), a carboxyl acid (-COOH), and a side chain (R). There are twenty naturally occurring amino acids, and each amino acid has a unique side- chain or R-group. Amino acids are connected by peptide bonds to form protein polymers. This gives rise to different levels of structure for proteins. The primary (1°) structure of a protein is a made up of a string of amino acids connected via peptide bonds. The secondary (2°) structure of a protein is formed by the coiling and folding of the 1° structure, due to hydrogen bonding. At this level, structures called alpha-helices and beta-sheets are visible. The tertiary (3°) structure of a protein is formed by interactions between the components of the 2° structure. Some proteins have quaternary (4°) structure, which includes the assembly of multiple individual subunits to form the functional protein. Proteins have numerous biological functions. The common types of proteins that are found in biological systems are enzymes, antibodies, transport proteins, regulatory proteins, and structural proteins. In today’s lab we will be using the Biuret reagent to identify the presence of proteins in different solutions. Biuret’s reagent turns purple in the presence of peptide bonds, pink in the presence of low amounts of peptide bonds, or remains blue if there’s no peptide bonds. Question: Which common household items will test positive for proteins? Hypothesis: Hypothesize what will be the color change (blue, purple, pink, etc.), if any, for each solution. Record your prediction in Table 3 below. Materials:  Biuret Solution  Distilled Water  Glucose Solution  Starch Solution  Milk  Sugar-Free Energy Drink  Albumin Solution (egg whites)  6 Test tubes  Test tube rack  7(1 mL) Serological Pipets and pumps  Wax Pencil  Timer  Paper and pencil Procedure: 1. Label tubes. Use a wax pencil to label the tubes with the test tube 1-6.

2. Add 1 mL of corresponding solution to each test tube. Be sure to add the solutions based on the test tube number listed on the table below. Record the initial color of the solutions in Table 3 . 3. Add 1 mL of Biuret solution to each test tube and swirl to mix. 4. Wait 2 minutes, then record color after biuret. 5. Dispose of solutions in the waste container when done. Results: (Watch the Lab 4. Chemical Composition of Cells video) Table 3: Results for Testing for Proteins Test Tube # Sample Hypothe sis Initial Color Color after Biuret Conclusion 1 Distilled water Blue Blue Blue No peptide bonds (no protein present); Negative 2 Glucose Blue to Black (as per my toddler) Blue Dark bluish to purple Presence of peptide bonds (protein present); Positive 3 Starch Bluish Blue Blue No peptide bonds (no protein present); Negative 4 Milk Purple Blue Purple Presence of peptide bonds (protein present); Positive 5 Sugar Free Energy Drink Green Blue Blue No peptide bonds (no protein present); Negative 6 Albumin Purple Blue Purple Presence of peptide bonds (protein present); Positive

 " Biomolecule Detection " by LibreTexts is licensed under CC BY-NC-SA .  " Biological Molecules " by Susan Burran and David DesRochers , LibreTexts is licensed under CC BY-SA .  " Biomolecules " by Ellen Genovesi, Laura Blinderman, & Patrick Natale , LibreTexts is licensed under CC BY .