Lab #3 Chemistry of Life - E Science Labs PDF

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E Science Labs Chemistry of Life...

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The Chemistry of Life PRE-LAB QUESTIONS 1. Nitrogen fixation is a natural process by which inert or unreactive forms of nitrogen are transformed into usable nitrogen. Why is this process important to life? According to our lab workbook, “more than 90% of all matter is composed of combinations of oxygen, carbon, hydrogen, and nitrogen”. We need a usable form of nitrogen for many things such as the building blocks of DNA and amino acids to form protein. 2. Given what you have learned about the hydrogen bonding shared between nucleic acids in DNA, which pair is more stable under increasing heat: adenine and thymine, or cytosine and guanine? Explain why. Adenine and thymine are composed of only two hydrogen bonds. Whereas, cytosine and guanine consist of three hydrogen bonds, which make them more stable under increasing heat.

3. Which of the following is not an organic molecule: methane (CH 4), fructose (C 6H12O6), rosane (C20H36), or ammonia (NH3)? How do you know? Ammonia (NH3) is not an organic molecule because organic molecules typically contain a carbon backbone and or carbon-hydrogen bonds. Ammonia is made up of only Nitrogen and Hydrogen and therefore is not organic.

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The Chemistry of Life EXPERIMENT 1: TESTING FOR PROTEINS Data Tables Table 1: Testing for Proteins Results Sample 1. Albumin Solution 2. Gelatin Solution 3. Glucose 4. Water 5. Unknown

Initial Color

Final Color

Is Protein Present?

Milky white

violet

present

Slightly cloudy/ clear clear

violet

present

Bluish/clear

Not present

clear

Bluish/clear

Not present

Milky white

Milky blue

Not present

Post-Lab Questions 1. Record your hypothesis about what will happen when Biuret solution is mixed with the solutions from test tubes 1, 2, 3, and 4 here. Be sure to use scientific reasoning to support your hypothesis. When the Biuret solution is mixed with test tubes 1 and 2 it will result in the presence of proteins because egg whites and gelatin contain proteins. Whereas, when the Biuret solution is mixed with test tubes 3 and 4 it will result in the absence of proteins because glucose is a monosaccharide and water does not contain proteins. 2. Write a statement to explain the molecular composition of the unknown solution based on the results obtained during testing with the Biuret solution and each sample solution. The unknown solution did not turn violet or pink when the Biuret solution was applied. It instead turned a bluish color. This means it does not contain either short © eScience Labs, 2018

The Chemistry of Life peptides or long polypeptides. 3. Diet and nutrition are closely linked to the study of biomolecules. How should you monitor your food intake to ensure the cells in your body have the materials necessary to function? Most of us think we eat a pretty healthy diet, but after tracking our dietary intake for a few days, one may be surprised to find that we are either not reaching our daily needs of vitamins and minerals and the daily percentage of macronutrients is way off balance. Living a sedentary lifestyle and consuming too many calories or too much of a certain macronutrient such as carbohydrates leads to an excess of fat/energy storage. There are also a lot of fad diets like the most current craze of Keto, where people consume extremely low amount of carbohydrates and increase their lipid intake in hopes of pushing their body to tap into fat storage for energy without the primary source of carbs to use. This may work at first but is this healthy long term? Our bodies are meant to consume a healthy balance of the three macronutrients: fats, proteins, and carbohydrates to function at our best. 4. There are other types of reagents used to determine what type of biomolecule a substance is. For example, copper ions present in Benedict’s reagent reacts with the free end of any reducing sugars, such as glucose, when heated. Originally blue in color, these copper ions are reduced by the sugar, and produce an orange-red colored precipitate. Alternatively, iodine-potassium iodide (IKI) may also be used when working with starch. IKI contains special tri-iodine ions which interact with the coiled structure of a starch polymer. Prior to a reaction, the IKI displays a yellow-brown color; however, after reacting with starch, a dark purple or black color is presented. The molecule pictured below produced a blue color when tested with Benedict’s reagent, a yellow color when tested with IKI, and a violet color when tested with Biuret reagent. Based on the structure shown below and these chemical results, what kind of biomolecule is this? It is a protein, because it changed to a violet color when tested with the Biuret reagent. © eScience Labs, 2018

The Chemistry of Life

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