chemistry experiment

DNA Report Sheet Post-Lab Questions Answering these questions may require you to do some web-based research. Please be sure to cite any sources you use, including images. 1. Post a ‘Science Selfie’ from Part I of the experiment. Be sure to include a description. 2. Structurally, what are the differences between ribose and deoxyribose? 3. What are the biological roles of DNA and RNA? What are the biological advantages for one biomolecule to be made of deoxyribose while the other is comprised of ribose? 4. What is a free radical? What is an antioxidant? 5. Describe, in detail, why free radicals can be so damaging to living organisms. 6. Post the picture of from Part II of the experiment. Provide a short summary of your observations. Do your observations support the biological significance of antioxidants in your diet? Why or why not? 7. There are many whole foods that can supply a variety of antioxidants. List one food source that is relatively high in antioxidants and the primary antioxidant found in this food. The antioxidant that you select should be something other than vitamin C. 8. Using the antioxidant selected in question 7, post a picture that shows the structure of the antioxidant and identify any functional groups contained within the molecule. 9. Generally, what types of functional groups are best at neutralizing free radicals? Does the antioxidant you selected from question 8 support this? Isolation of Deoxyribonucleic Acid (DNA) and the Analysis of Ascorbic Acid (Vitamin C) as an Antioxidant Background Free radicals can be defined as any atom, ion, or molecule with an unpaired electron. Many molecules with unpaired electron are highly unstable and are therefore extremely reactive. In our bodies, free radicals are generated as a by-product of cellular respiration, equation 1. The extremely reactive hydroxyl radical (OH) causes chain reactions that can potentially damage surrounding tissues and, at the molecular level, important biomolecules such as lipids, proteins, and DNA. Free radicals have been closely associated with the aging process, degenerative diseases and cancer. Equation 1: Formation of a hydroxyl radical. H2O + energy (usually cellular respiration) → H2O+ + eH2O+ → H+ + OH Figure 1: Comparison of the hydroxide ion and the hydroxyl free radical. Vitamin C is one of the many molecules that can be classified as an antioxidant. An antioxidant is any atom, ion, or molecule capable of ‘neutralizing’ a free radical. Many antioxidants work by accepting the unpaired electron from a reactive free radical species. As a result, the antioxidant itself is converted into a free radical. However, these molecules are special in that they are able to form relatively stable free radicals. Specifically the ascorbic acid free radical can readily be converted back into normal ascorbic acid by cellular enzymes. It is less likely that crucial biomolecules such as DNA will be damaged by free radicals in the presence of an antioxidant. Equation 2: Neutralization of a free radical (R) by ascorbic acid, AscH- (vitamin C). Image retrieved from https://benbest.com/nutrceut/. In this experiment you will extract DNA from strawberries and then expose the isolated DNA to free radicals in the presence and absence of an antioxidant (vitamin C). The free radical will be generated artificially in the laboratory by the reaction shown below in equation 3. Equation 3: Generation of a hydroxyl (OH) by the reaction of FeSO4 with hydrogen peroxide. Fe2+ + H2O2 → Fe3+ + OH + OH1- Required Materials • • • • • • • • • • 2-3 strawberries Dish soap (Dawn works best) Coffee filter Wooden coffee or popsicle stick 2 plastic cups Large resealable (Ziplock) plastic bag Rubbing alcohol (isopropyl alcohol or isopropanol) **It is critical that the isopropanol is kept cold. Place in the freezer overnight prior to beginning the experiment and keep cold until you are instructed to use it in Part I. Hydrogen peroxide (typically 3%) Wax paper Sheet of white paper Safety • • • Goggles must be worn at all times. Isopropanol is flammable, keep away from sparks and open flames. In case of contact with skin, flush area with water. Hydrogen peroxide is corrosive and can be harmful to mucous membranes such as your eyes. Handle with caution. In case of contact with skin, flush area with water. Procedure Solution Preparation Prior to beginning the experiment, you will need to prepare two solutions (1 M ascorbic acid and 0.1 M FeSO4) using the materials supplied in your lab kit. Detailed instructions are provided below. Be sure to clearly label each solution. Once you have completed the solution preparation, set the labeled solutions aside until you are instructed to use them in Part II of the experiment. Preparation of a 1 M Ascorbic Acid Solution 1. You have been supplied with approximately 1 g of ascorbic acid in a small snapcap tube. Pour the ascorbic acid into a cup. 2. Using a 10 mL graduated cylinder, measure out 4.0 mL of water and add it to the cup containing the ascorbic acid. 3. Stir the ascorbic acid until it is dissolved. 4. Label and reserve this solution for Part II of the experiment Preparation of a 0.1 M FeSO4 (Ferrous Sulfate) Solution 1. You have been supplied with approximately 0.5 g of FeSO4·7H2O in a small snapcap tube. Empty the contents into a cup. 2. Measure out 8.0 mL of water in 10 mL graduated cylinder and pour it into the cup containing the FeSO4. 3. Stir the FeSO4·7H2O until it is dissolved. 4. Label and reserve this solution for Part II of the experiment Part I: 1. Follow the instructions for Isolating DNA From a Strawberry. 2. Take a ‘science selfie’ with your isolated DNA, similar to the image from the Background and Procedure page. Part II: WARNING: Hydrogen peroxide can burn your skin and therefore contact with mucous membranes and skin should be avoided. You will now need the 1 M ascorbic acid and 0.1 M FeSO4 solutions prepared at the begging of the experiment. 1. Using a wooden stick such as a popsicle or coffee stick, carefully scoop out the isolated strawberry DNA a place two samples of equal size on a piece of wax paper laid on top of a piece of what paper (this will make it easier to observe the changes). Label one ‘CONTROL’ and the other ‘ANTIOXIDANT’. 2. Add 5 drops of water to the first DNA sample and gently swirl to mix. Then add 5 drops of the 0.1 M FeSO4 followed by 10 drops of 3% hydrogen peroxide (H2O2). Record your observations. 3. Add 5 drops of the 1 M ascorbic acid (vitamin C) to the second DNA sample and gently swirl to mix. Then add 5 drops of 0.1 M FeSO4 followed by 10 drops of 3% hydrogen peroxide (H2O2). 4. Take a picture of each sample and record your observations.

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