Macromolecule Lab PDF

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detailed practice work of macromolecules...

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Biology 1124

2020 edition

MACROMOLECULES Identification and analysis By the end of this lab you should be able to: 1. Test for the presence of specific macromolecules using a variety of chemical reagents. 2. Perform an experiment using positive and negative controls and explain their purpose. 3. Collect, organize, and analyze data. 4. Use chemical reagents to identify the composition of unknown substances.

Macromolecules

Background A cell can be compared to a living chemistry laboratory. Most of the func9ons within the cell take the form of interac9ons between organic (carbon-containing) molecules. Organic molecules in living systems can be classified as carbohydrates, lipids, proteins, or nucleic acids. Each of these classes of molecules is made of smaller subunits, which can have specific proper9es that can be iden9fied by simple chemical tests. In this lab, you will learn how to iden9fy three of the four major types of organic molecules: lipids, proteins, and carbohydrates, as well as some of their smaller subunits.

Types of common macromolecules Carbohydrates, also known as “carbs” in the media are sugar molecules produced by plants. Simple sugars, also known as monosaccharides, consist of a single molecular unit and are oIen used to sweeten beverages. Glucose is an example of a simple sugar that is essen9al for cellular respira9on in our cells. Disaccharides consist of two monosaccharide molecules linked together. An example of a disaccharide is sucrose, which is table sugar. Polysaccharides are complex carbohydrates that involve a series of simple sugar units being polymerized into straight or branched chains. These polysaccharides macromolecules are commonly known as starches and are found in pasta and breads. An example of these three types of sugars are represented in Figure 1. Sugars are a source of energy for the body, but when excessive amounts are consumed, the sugar that was not used is converted into fat for long term energy storage. This has led to the misconcep9on by the general public that carbohydrates are fats rather than sugars.

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Figure 1. Examples of carbohydrates as a mono-, di-, and polysaccharide.

Lipids are the molecules that we commonly think of as fats, oils, and waxes. Lipids are easy to iden9fy based on their insolubility in water (Figure 2). Saturated fats are typically solid at room temperature and are found in sources such as meat and dairy. Unsaturated fats are typically liquid at room temperature, and they are classified as oils that can be extracted from plants. Membrane lipids are a group of compounds (similar to fats and oils) which form the double-layered surface of all cells (phospholipid bilayer). A phospholipid is a lipid made of glycerol, two faSy acid tails, and a phosphate-linked polar head. As temperatures lower, membranes switch from a fluid state to a solid state as the phospholipids are more closely packed. Membranes rich in unsaturated faSy acids are more fluid than those by saturated faSy acids, because the kinks in the unsaturated faSy acid tails prevent 9ght packing. The term “trans fats” refers to a specialized group of unsaturated fats that are created industrially to extend the shelf life of products and for baking. However, these fats are neither required nor beneficial for health and have been linked to increased risk of coronary disease.

Figure 2. Membrane fluidity

Macromolecules

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Proteins are polymers of amino acids that have a variety of func9ons based on their structure (Figure 3). Proteins are made by both plants and animals and are an important nutri9onal component of a balanced diet. Enzymes are specialized proteins that facilitate chemical reac9ons that would otherwise take far too long to reach equilibrium to be useful in sustaining life as we know it. Enzymes are biologically ac9ve, so they require a specific temperature and pH range for op9mal ac9vity. The advantage to using enzymes in chemistry is that they are very selec9ve with respect to what you want to measure.

Figure 3. Amino acid structure and their associated bonding to form a polypep8de chain

Complete the table and answer the 3 questions below before you arrive in lab: Table 1. Describe each category of biological macromolecule. Subunits/Monomers

Func?on(s) in the cell

Examples

Lipids

Proteins

Carbohydrates

Nucleic Acids

Macromolecules

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1. Explain why so many people have the misconcep9on that carbohydrates (a.k.a. “carbs”) are fats rather than sugars. 2. What is the purpose of having both a posi9ve and a nega9ve control?

3. Which single macromolecule test could be used to determine if a burger was indeed 100% allbeef rather than being a veggie burger?

What are we doing for todays’ experiment? In today’s experiment, you will test a variety of samples for the presence of protein, reducing sugars (e.g., glucose and fructose), and complex carbohydrates (starch) in various foods using qualita9ve and quan9ta9ve methods. For each test, you will use a posi9ve control (+) to illustrate what the reac9on will look like if the item in ques9on contains the macromolecule being tested for. You will also use a nega9ve control (-) to determine what the results will look like of the item in ques9ons does not contain the macromolecule being tested for. Table 2. Predict the biological macromolecules in the experiment samples Experimental Sample

Color of Sample Before Tes?ng

Hypothesized Organic Compound(s)

#1: Tofu #2: Hot dog #3: Whole milk #4: Red Bull

Testing for bio-organic molecules using reagents Sudan IV Test for Lipids 1. Prepare each test tube in accordance with the following table. 2. Indicate for each test tube if it was posi9ve (+) or nega9ve (-) for lipids based on comparison with the posi9ve and nega9ve control tubes. 3. Wash the test tubes out thoroughly, then proceed to the next test.

Macromolecules

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Table 3. Lipid data

Sample Reagents

Tube 1

Tube 2

Tube 3

Tube 4

Tube 5

Tube 6

(+) control

(-) control

Sample

Sample

Sample

Sample

2 mL Mineral Oil

2 mL water

2 mL

2 mL

2 mL

2 mL

10 Drops Sudan IV

10 Drops Sudan IV

10 Drops Sudan IV

10 Drops Sudan IV

10 Drops Sudan IV

10 Drops Sudan IV

Observa?ons Got Lipids?

Benedicts Test for Reducing Sugars 1. Prepare each test tube in accordance with the following table. 2. Mix each tube gently and place them in a boiling water bath for a least three minutes. 3. Carefully remove from the water bath (the tube will be hot) and record your observa9ons. 4. Indicate for each test tube if it was posi9ve (+) or nega9ve (-) for reducing sugars. 5. Use the color change to determine the concentra9on of sugar. (green = low, yellow = medium, orange = medium high, red = high) 6. Wash the test tubes out thoroughly, then proceed to the next test. Table 4. Reducing sugars data

Sample Reagents

Tube 1

Tube 2

Tube 3

Tube 4

Tube 5

Tube 6

(+) control

(-) control

Sample

Sample

Sample

Sample

2 mL Glucose

2 mL water

2 mL

2 mL

2 mL

2 mL

10 Drops Benedicts

10 Drops Benedicts

10 Drops Benedicts

10 Drops Benedicts

10 Drops Benedicts

10 Drops Benedicts

Observa?ons Got Sugar? Sugar Concentra?on

Macromolecules

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Iodine Test for Starch 1. Prepare each test tube in accordance to the following table. 2. Mix each tube gently before recording your observa9ons. 3. Indicate for each test tube if it was posi9ve (+) or nega9ve (-) for starch. 4. Wash the test tubes out thoroughly, then proceed to the next test.

Sample

Tube 1

Tube 2

Tube 3

Tube 4

Tube 5

Tube 6

(+) control

(-) control

Sample

Sample

Sample

Sample

2 mL Starch

2 mL water

2 mL

2 mL

2 mL

2 mL

10 Drops Iodine

10 Drops Iodine

10 Drops Iodine

10 Drops Iodine

10 Drops Iodine

10 Drops Iodine

Reagents Observa?ons Got Starch?

Bradford Test for Proteins 1. Prepare each test tube in accordance with the following table. 2. Indicate for each test tube if it was posi9ve (+) or nega9ve (-) for protein based on comparison with the posi9ve and nega9ve control tubes. 3. Wash the test tubes out thoroughly. Table 6. Protein data Tube 1

Tube 2

Tube 3

Tube 4

Tube 5

Tube 6

(+) control

(-) control

Sample

Sample

Sample

Sample

Sample

2 mL Albumin

2 mL water

2 mL

2 mL

2 mL

2 mL

Reagents

10 Drops Bradford

10 Drops Bradford

10 Drops Bradford

10 Drops Bradford

10 Drops Bradford

10 Drops Bradford

Observa?ons Got Protein?

Macromolecules

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