Life Chemistry Lab (BIOL 1103L) PDF

Learning Goals By the end of this unit, you should be able to do the following: 1. Cho...

Learning Goals By the end of this unit, you should be able to do the following: 1. Choose the proper chemical to use in identifying starch, simple sugars, proteins, and lipids. Life Chemistry 2. Describe the color of a positive and negative result for each chemical test. BIOL 1103L - Ex. # 4 3. Identify the Independent, Dependent, and Control Variables in your experiment. 4. Identify the positive and negative control experiments from each chemical test. 5. Write a lab report summarizing your findings. 1 2 Organic Molecules Carbohydrates - Monosaccharides Organic molecules contain carbon and A monosaccharide is a single sugar hydrogen atoms. molecule. Also called simple sugars Four classes of organic molecules (biomolecules) exist in living organisms: Carbohydrates Examples: Lipids – Glucose (blood), fructose (fruit) and Proteins galactose Nucleic Acids – Ribose and deoxyribose (in nucleotides) 3 4 3 4 Carbohydrates - Disaccharides Carbohydrates - Polysaccharides A polysaccharide is a polymer of A disaccharide contains two monosaccharides. monosaccharides (many monosaccharides Also called simple sugars linked together). Examples: Examples: – Lactose (milk sugar) is composed of galactose and  Starch provides energy storage in plants. glucose.  Glycogen provides energy storage in animals. – Sucrose (table sugar) is composed of glucose and  Cellulose is found in the cell walls of plants. fructose. – Maltose is composed of two glucose molecules. 5 5 6 1  Proteins Lipids Proteins are polymers of amino acids Lipids are varied in structure. Large nonpolar molecules that are insoluble Two or more amino acids joined together are in water (do not mix with water) called peptides.  Long chains of amino acids joined together are called polypeptides. Examples: A protein is a polypeptide that has folded into a fats, oils, phospholipids, steroids, waxes particular shape and has function. 7 7 8 Identification Tests Iodine Solution Test for Starch 1. Iodine solution test for starch (polysaccharide, Lugol’s reagent contains iodine and potassium iodide complex sugars) (I2KI). It changes from a yellowish-brown to blue-black in the presence of starch. 2. Benedict’s reagent test for simple sugars Left to right: – monosaccharides (have one subunit) and disaccharides Lugol's iodine (LI), (have two subunits) starch solution, starch solution + LI. 3. Biuret’s reagent test for protein Results: Yellow-orange = negative. Purple-black = positive. 4. Beta carotene test for lipids (fats) 9 10 Benedict's Reagent Test for Simple Sugars Benedict's Reagent Test for Simple Sugars Left to right: Benedict's reagent (BnR), potato extract + BnR, onion extract + BnR, 5% glucose + BnR. Results: Aqua-blue to green = negative. Yellow to orange = positive. Note: this test cannot detect the simple sugar sucrose. 11 12 2  Biuret's Reagent Test for Protein Beta Carotene Test for Lipids Left to right: Lipids – oils, fats, waxes, steroids Biuret's reagent (BrR), Are hydrophobic (do not mix with water), are not water + BrR, soluble in water egg albumin solution, egg albumin solution+ BrR. Beta carotene is fat-soluble (dissolves in fat) Is Beta carotene hydrophobic or hydrophilic? Results: Denim-blue = negative. Lavender = positive. A. B. Beta carotene in Beta carotene in a ____________ a ___________ solution. solution. 13 14 Emulsification Websites Emulsifiers are molecules have both polar http://faculty.uca.edu/johnc/mole1440.htm and nonpolar parts and thus are capable of http://www.ausetute.com.au/redsugar.html dissolving in or interacting with both lipids https://www.youtube.com/watch?v=1Dx7LDwINLU and water. https://www.youtube.com/watch?v=Plc4ENFMCYU When emulsifiers are mixed with lipids and water, they may act to suspend small https://www.youtube.com/watch?v=4dbkAGcQ8mM droplets of the lipid in water. The lipid is not dissolved in water, but is broken into smaller fragments that may remain suspended for long periods of time. Examples of emulsifiers are: Twee, bile salt, detergent 15 16 3