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Objectives

Students should be able to:

  1. Describe the formation of inorganic molecules and ions associated with living organisms

  2. Describe the formation of the basic groups of organic molecules associated with living organisms

  3. Build models of inorganic and organic molecules, and ions

  4. Describe how to test for the four groups of organic molecules associated with living organisms, carbohydrates, proteins, lipids, and nucleic acids

  5. Describe the major inorganic molecules associated with living organisms

  6. Test for the presence of carbohydrates (starches, sugars) proteins, and lipids (fats, oils)

  7. Perform the following tests used to determine types of organic molecules: Benedict's reagent, Biuret reagent, Iodine, paper penetration and Sudan staining.

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Introduction

All living matter is composed of basic units of matter called atoms. Atoms can chemically bond to form molecules. The chemical bonding of atoms can be ionic (atoms are held together by electronic attraction due to gain or lose of the atom's electrons) or they can be covalent (atoms "share" their electrons). You will study these two types of bonding this laboratory exercise.

The chemical bonding of atoms forms either ionic bonds (formula units), or covalent bonds (molecules). In ionic bonding, atoms lose or gain electrons. If an atom loses electrons it is termed a cation. If it gains electrons then it becomes an anion.

Chemically bonded compounds can be either inorganic or organic. Inorganic compounds are generally ionically bonded, while organic compounds are covalently bonded.

This lab will concentrate more on the organic compounds. Their structure, composition, chemical properties, and importance to living organisms will be addressed. There are four major classes of organic compounds. They are carbohydrates (sugars and starches), proteins, lipids (fats and oils) and nucleic acids (DNA and RNA).

Large organic molecules (ones with 1000's of atoms) are formed from smaller units called monomers. Monomers, such as glucose sugar, chemically bond together by dehydration synthesis (water is formed). These chemically bonded monomers (chains, rings, etc.) form polymers, such as starch. the bonded polymers can be broken apart by the addition of water (and enzymes), in a process called hydrolysis.

Carbohydrates are a group of important organic compounds. They consist of sugars, which can be classified as monosaccharides, or disaccharides, or starches, which can be polysaccharides or oligosaccharides. The monomer of carbohydrates is usually the monosaccharide, glucose (C6H12O6) It is chemically bonded (dehydration synthesis) to other glucose molecules or other sugars to form large single or branched chains or sometimes rings. You will be building models of glucose and chemically testing for sugars and starches in this lab exercise.

Proteins are another group of important organic compounds. The are formed from monomer units called amino acids. There are 20 types of amino acids, that can go into the formation of proteins. Each amino acid consists of a central carbon atom, to which is chemically bonded four other chemical entities. These include an amino group, a carboxyl group (organic acid), an R group (which is what determines the kind of amino acid) and a hydrogen atom. You will be building amino acid models and chemically testing for proteins in this lab exercise.

Lipids, fats and oils, are important to living organisms too. They are formed by chemically bonding fatty acids to a glycerol base. Fats are generally insoluble in water, but soluble in alcohols and ether. Fats are generally solids, whereas oils are liquid. Fats are generally associated with animals and oils with plants. There are many types of lipids that have biological significance. These are fats, oils, phospholipids (form cell membrane), cholesterol and steroids (not a true lipid). You will be building models of the glycerol, and chemically testing for lipids in this lab exercise.

Nucleic acids, DNA and RNA, are important molecules from a genetic and functional standpoint. Nucleic acids are formed from nucleotide units. The nucleotides found in the DNA molecule are adenine, thymine, guanine and cytosine. In RNA the same ones are found except uracil replaces thymine. You will be building a model of DNA during this lab exercise.

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Pre-lab Activity

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Print out the following materials. Make sure you read them before coming to lab.

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Molecular Modeling Exercise

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Data Collection Sheet (html version)

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Data Collection Sheet (Word version)

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Pre-Lab Questions (html version)          Pre-Lab Questions (Word version)

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The Laboratory Activities and Data Collection

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Lab Activity #1 - Molecular Modeling

Materials:

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Molecular Modeling Exercise

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Molecular modeling kit

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DNA modeling kit

Procedures:

  1. Follow the procedures and directions set forth in the Molecular Modeling Exercise and the DNA Modeling Kit

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Lab Activity #2 - Chemical Testing for Carbohydrates - Starch

Materials:

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5 Culture tubes (10mm x 75mm)

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Distilled water

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Starch solution

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Glucose solution

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Potato extract solution

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Onion extract solution

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Iodine solution

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Test tube Rack

Procedures:

  1. Using a metric ruler and a marking pen label the tubes 1 - 5 and then mark each tube at the 1 cm level (measure from the bottom of the tube).

  2. Tube 1 - Fill tube 1 to the 1 cm mark with distilled water. Add five drops of iodine solution. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  3. Tube 2 - Fill tube 2 to the 1 cm mark with starch solution. Add five drops of iodine solution. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  4. Tube 3 - Fill tube 3 to the 1 cm mark with glucose solution. Add five drops of iodine solution. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  5. Tube 4 - Fill tube 4 to the 1 cm mark with potato extract solution. Add five drops of iodine solution. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  6. Tube 5 - Fill tube 5 to the 1 cm mark with onion extract solution. Add five drops of iodine solution. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  7. When you are finished with this activity empty the contents of each test tube into the waste container provided by the instructor and place the empty test tubes into the container provided by the instructor.

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Lab Activity #3 - Chemical Testing for Carbohydrates - Sugars

Materials:

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5 Culture tubes (10mm x 75mm)

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Distilled water

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Starch solution

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Glucose solution

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Potato extract solution

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Onion extract solution

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Benedict's Solution

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Test tube Rack

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Tongs

Procedures:

  1. Using a metric ruler and a marking pen label the tubes 1 - 5 and then mark each tube at the 1 cm level and at the 3 cm level (measure from the bottom of the tube).

  2. Tube 1 - Fill tube 1 to the 1 cm mark with distilled water and then add Benedict's solution until the solution in the tube reaches the 3 cm mark. Stir tube as directed by the instructor. Note the initial color and record it on your Data Collection Sheet. Heat the tube in the water bath for 5 minutes and note any color change. Record your results on the Data Collection Sheet.

  3. Tube 2 - Fill tube 2 to the 1 cm mark with glucose solution and then add Benedict's solution until the solution in the tube reaches the 3 cm mark. Stir tube as directed by the instructor. Note the initial color and record it on your Data Collection Sheet. Heat the tube in the water bath for 5 minutes and note any color change. Record your results on the Data Collection Sheet.

  4. Tube 3 - Fill tube 3 to the 1 cm mark with starch solution and then add Benedict's solution until the solution in the tube reaches the 3 cm mark. Stir tube as directed by the instructor. Note the initial color and record it on your Data Collection Sheet. Heat the tube in the water bath for 5 minutes and note any color change. Record your results on the Data Collection Sheet.

  5. Tube 4 - Fill tube 4 to the 1 cm mark with potato extract solution and then add Benedict's solution until the solution in the tube reaches the 3 cm mark. Stir tube as directed by the instructor. Note the initial color and record it on your Data Collection Sheet. Heat the tube in the water bath for 5 minutes and note any color change. Record your results on the Data Collection Sheet.

  6. Tube 5 - Fill tube 5 to the 1 cm mark with onion extract solution and then add Benedict's solution until the solution in the tube reaches the 3 cm mark. Stir tube as directed by the instructor. Note the initial color and record it on your Data Collection Sheet. Heat the tube in the water bath for 5 minutes and note any color change. Record your results on the Data Collection Sheet.

  7. When you are finished with this activity empty the contents of each test tube into the waste container provided by the instructor and place the empty test tubes into the container provided by the instructor.

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Lab Activity #4- Chemical Testing for Proteins

Materials:

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4 Culture tubes (10mm x 75 mm)

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Distilled water

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Pepsin solution (enzyme)

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Egg albumin solution

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Starch solution

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Biuret reagent (Safety Concern - note instructor's explanation)

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Test tube Rack

Procedures:

  1. Using a metric ruler and a marking pen label the tubes 1 - 4 and then mark each tube at the 1 cm and 2 cm level (measure from the bottom of the tube).

  2. Tube 1 - Fill tube 1 to the 1 cm mark with distilled water and then add biuret reagent until the solution in the tube reaches the 2 cm mark. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  3. Tube 2 - Fill tube 2 to the 1 cm mark with egg albumin solution and then add biuret reagent until the solution in the tube reaches the 2 cm mark. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  4. Tube 3 - Fill tube 3 to the 1 cm mark with pepsin solution and then add biuret reagent until the solution in the tube reaches the 2 cm mark. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  5. Tube 4 - Fill tube 4 to the 1 cm mark with starch solution and then add biuret reagent until the solution in the tube reaches the 2 cm mark. Stir tube as directed by the instructor. Note any color change. Record your results on the Data Collection Sheet.

  6. When you are finished with this activity empty the contents of each test tube into the waste container provided by the instructor and place the empty test tubes into the container provided by the instructor.

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Lab Activity #5 - Chemical Testing for Lipids

Materials:

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2 Culture tubes (10mm x 75 mm)

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Vegetable or mineral oil in dropper bottle

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Animal "fat"

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Cotton tipped swab

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3 pieces of brown paper (small squares)

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Distilled water

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"Emulsifier" in dropper bottle

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Test tube Rack

Procedures:

Fats and Oils

  1. Place a drop of distilled water on the first small square of brown paper. Note what occurs. Place this result on your Data Collection Sheet.

  2. Place a drop of oil on the second small square of brown paper. Note what occurs. Place this result on your Data Collection Sheet.

  3. Rub a cotton tipped swab dipped in animal fat on the third small square. Note what occurs. Place this result on your Data Collection sheet.

  4. Wait 5 minutes and observe these brown papers again. Note what happened. Place these results on your Data Collection Sheet.

Emulsifiers

Using a metric ruler and a marking pen label the 2 tubes 1and 2. Then mark tube #1 at the 3 cm and 4 cm level (measure from the bottom of the tube). Mark tube #2 at the 2 cm, 3 cm and 4 cm level (measure from the bottom of the tube).

  1. Tube 1 - Fill tube 1 to the 3 cm mark with distilled water and then add oil until the solution in the tube reaches the 4 cm mark. Shake the tube as directed by the instructor. Note what occurs. Record your results on the Data Collection Sheet.

  2. Tube 2 - Fill tube 2 to the 2 cm mark with distilled water, add oil until the solution in the tube reaches the 3 cm mark. Then add an emulsifier until the 4 cm mark is reached. Shake the tube as directed by the instructor. Note what occurs. Record your results on the Data Collection Sheet.

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Post-lab Activity and Data Analysis

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Results and Analysis:

  1. Turn in the Post-Lab Questions, Completed Data Collection Sheet and the Chemical Modeling Exercise to satisfy the results and analysis section for this lab.

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Post-Lab Questions (html version)    Post-Lab Questions (Word version)

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