LAB 22: CARBOHYDRATES:

Transcription

1 LAB 22: ARBYDRATES: STRUTURE AND PRPERTIES PURPSE: To use physical and chemical tests to distinguish between simple and complex carbohydrates. To apply the chemistry of carbohydrates to cooking. SAFETY NERNS: Always wear safety goggles. oncentrated Sulfuric Acid is dangerous to skin, eyes, and clothes. Wash with soap and copious amounts of water if contacted. ARBYDRATES: arbohydrates are the major components of plants, comprising 60 to 90% of their dry weight. They are produced by the process of photosynthesis in green leaves. SIMPLE ARBYDRATES: The common small, or simple carbohydrates, are made of one (mono) or two (di) units. Glucose, galactose, and fructose are simple monosaccharides that combine to form disaccharides such as maltose, lactose, and sucrose. Examples of Monosaccharides: Examples of Disaccharides: Fructose ommon Source: In honey Glucose ommon Source: In fruits, vegetables, corn syrup Structure Sucrose ommon Source: In sugar cane and sugar beets Lactose ommon Source: In Milk Structure 106 Lab 22: arbohydrates (W16) 13

2 MPLEX ARBYDRATES: The complex carbohydrates amylose, and cellulose are long chain polymers of the simple carbohydrate glucose. Examples of omplex arbohydrates: (Polysaccharides) Structure Amylose: Polymer of -D-glucose ommon Source: Starches: Rice, wheat, potatoes, beans ellulose: Polymer of -D-glucose ommon Source: Plant Fibers: otton, wood, stems, leaves n n Amylose, and its branched relative, amylopectin, are major components of starches, the energy storage carbohydrates found in tubers and edible roots. Amylose and amylopectin are polymers of D-glucose in which the anomeric carbon of each glucose unit is in the alpha ( ) form. ellulose is plant structure material like that of wood, stems, and leaves. The major function of cellulose for us is not as a source of glucose for energy, but rather as fiber to keep our digestive tract clean. ellulose is a polymer of D-glucose in which the anomeric carbon of each glucose unit is in the beta ( ) form. SWEETNESS: Simple carbohydrates are called saccharides from the Latin term saccharum (sweet) because of their sweet taste. Many of the small carbohydrates, mono and disaccharides, are used as sweeteners. They fit into the taste receptor sites on our tongues and send the signal to our brains that we call sweet. Artificial sweeteners mimic the shape of the simple sugars and will fit into the same taste receptor sites that natural sugars do and so send to our brains a similar sweet signal. Artificial sweeteners are not metabolized in the same way as natural sugars. Examples of Artificial Sweeteners: Structure Structure Sucralose Aspartame ommon Source: Splenda (600X sweetness of sucrose) Saccharin ommon Source: Sweet N Low (400X sweetness of sucrose) l l S N l ommon Source: NutraSweet Equal (200X sweetness of sucrose) Neotame (13,000X sweetness of sucrose) N N 2 2 N N Lab 22: arbohydrates (W16)

3 SLUBILITY: Mono and Disaccharides are soluble in water since they have many exposed s along their surfaces which can easily hydrogen bond with water. Larger carbohydrates can still be soluble depending on the positioning of their s. If the s are abundant on the exterior of a carbohydrate (even a large one) then hydrogen bonding with water can occur and the carbohydrate can be made to dissolve in water. If, however, there is internal hydrogen bonding within a carbohydrate, or coiling that may prevent water from hydrogen bonding to the s, then the carbohydrate will not dissolve in water. Starch granules, tightly coiled strands of amylose and amylopectin, are not soluble in water at ordinary temperatures and so are convenient forms in which to store the plant s excess energy supplies. Roots and seeds are the organs in which starch is usually concentrated. Forms of amylose starch can be made to be soluble by heating in water so as to disrupt the solid packing of the strands. The coils unravel into long strands of amylose which have s more exposed to hydrogen bond with water. Not only are the uncoiled strands more water soluble but they can also tangle with each other to form gels. We often use these unraveled starch strands as thickeners in cooking or for stiffening fabrics. Although there are some forms of soluble fiber (like in oatmeal), most plant cellulose is not water soluble even with heating. ellulose strands have a lot of internal hydrogen bonding with themselves and each other. They form tight, twisted cables that make very strong structure material that does not unravel even in hot water. EMIAL REATINS F ARBYDRATES: Benedict s Test for Reducing Sugars: All of the monosaccharides and most of the disaccharides can be oxidized. When their cyclic (furanose or pyranose) hemiacetal structures open an aldehyde group formed, =, is available for oxidation to a carboxylic acid. Benedict s reagent, a basic solution of opper (II) Sulfate, (us 4 in Na) is commonly used for this purpose. The oxidizing agent, us 4, is blue in color which is characteristic of many u 2+ compounds. When the blue u 2+ of us 4(aq) causes the sugar aldehyde to oxidize it becomes reduced itself to u 1+ in the form of opper I oxide, u 2 (s) which is a brick red precipitate. A sugar that reduces blue u 2+ to brick-red u 1+ is called a reducing sugar. The color of the precipitate varies from green to gold to red depending on the concentration of the reducing sugar. u +2 (blue) 106 Lab 22: arbohydrates (W16) 15 + u 1+ (brick red) Glucose Gluconic Acid Tests for reducing sugars are commonly performed in medicine to identify the simple sugars present in blood or urine that may be indicators of metabolic problems or disease. Ketoses also act as reducing sugars because the ketone group on carbon 2 isomerizes in the presence of the base present in the Benedict s reagent (Na) to give an aldehyde group on carbon 1 than can then be oxidized. Fructose Na Isomerized to an aldehyde Sucrose is not a reducing sugar because it has no hemiacetal groups. Under the conditions of the Benedict s reagent, the acetal groups of the 1,2-glycosidic bond of sucrose cannot convert to open-chain aldehydes that would oxidize.

4 Seliwanoff s Test for Ketoses vs Aldoses: When monosaccharides are mixed with hot hydrochloric acid and resorcinol (Seliwanoff s reagent) ketohexoses will quickly produce a red color but aldohexoses will react slower and produce a light orange-pink color. This test is most sensitive for fructose, which is a ketose. Any polysaccharides or disaccharides tested will hydrolysis to monosaccharides in the aqueous hydrochloric acid of the reagent. Monosaccharides + Resorcinol l, 2 heat Ketoses = Red Aldoses = Pink Iodine Test for Polysaccharides: Amylose, the unbranched chain polymer of -D-glucose in starch, coils into tight spirals. Elemental iodine, I 2, which is normally yellow-brown in color, will fit inside the amylose coil and complex with the s inside the spiral. The resulting amylose-iodine complex is a deep blue-black color. Amylose elix I 2 (yellow/brown) I 2 I 2 I 2 I 2 I 2 Amylose/I 2 omplex (blue/black) Iodine, I 2, is commonly used as a test for the presence of amylose starch. Legal U.S. dollar bills made from a linen fabric will not react with iodine; however, the mark of the iodine pen on bills made from starched paper will show the characteristic dark blue sign of a counterfeit. ydrolysis of Disaccharides & Polysaccharides: Each bond connecting monosaccharide units (the glycoside bond) can be broken by hydrolysis; the reaction with water in the presence of a catalyst. Disaccharides can thus be hydrolyzed into two monosaccharides. Long chain polysaccharides can be hydrolyzed into shorter chains or further into simple sugars. In the laboratory we can catalyze sugar hydrolysis reactions with acid, or we can use catalytic enzymes that are specific for each carbohydrate. Sucrose is hydrolyzed into glucose and fructose by catalysis with the enzyme, sucrase. Maltose hydrolyses into glucose with maltase. Lactose hydrolyses into galactose and glucose with lactase. +, 2 or + Sucrase Sucrose Glucose Fructose Amylose and amylopectin are easily hydrolyzed into shorter chains of glucose called dextrins which are then further hydrolyzed into the disaccharide maltose and then to glucose (blood sugar) itself. In our bodies the hydrolysis of starches in digestion is catalyzed by the enzymes amylase and maltase. People vary in the amount of amylase in their saliva or urine. Starch (Amylose, Amylopectin) +, 2 or Amylase Dextrins +, 2 +, 2 or Maltoses or D-Glucoses Amylase Maltase 16 The hydrolysis of cellulose can be catalyzed in the laboratory with acid or by the enzyme cellulase found in certain bacteria. The human body does not contain the enzyme cellulase and so cannot convert cellulose into glucose for use as an energy source. Therefore, the long chain of cellulose stays intact for use as fiber. 106 Lab 22: arbohydrates (W16)

5 Digestion & Absorption: Before the cells of your body can utilize the energy stored in carbohydrates present in your diet, the carbohydrates must be digested and absorbed. Digestion is the process by which complex molecules are broken down (hydrolyzed) into simple molecules. These simple molecules pass through the intestinal wall into the bloodstream during absorption. The digestion of carbohydrates begins in the mouth as teeth tear food into tiny pieces; smaller pieces have a greater surface area and will be digested faster. Saliva contains the enzyme, amylase, that begins the hydrolysis of starch to dextrins and then to maltose. After swallowing, the food enters the stomach where protein and fat digestion begin but carbohydrate digestion temporarily ceases; the low p of the stomach s gastric juice inactivates the salivary enzymes. As food passes into the small intestine it is neutralized by alkaline pancreatic and intestinal juices. Those juices also contain an enzyme that renews the hydrolysis of complex carbohydrates. Eventually all polysaccharides and disaccharides are broken down to glucose, fructose, and galactose. These monosaccharides are small enough in size to pass through the intestinal wall and are absorbed into the blood. After circulating in the blood, fructose, and galactose are converted into glucose by the liver. The glucose in the blood may be immediately used to provide energy for cellular activities or it may be stored as glycogen in the liver and the muscles. Absorption is a form of dialysis; the movement of small molecules through a membrane. In Part II of this experiment a solution of starch and glucose will be placed inside a cellophane dialysis bag. After the dialysis bag has been immersed in water for a length of time, the water will be tested for the presence of starch and glucose. Dehydration; aramelization: When carbohydrates are either heated or reacted with acid, s and s combine and leave as water,. As water molecules begin to escape the carbohydrate begins to turn yellow, then brown, and then eventually black. If all of the s on a carbohydrate are removed as water then all that remains of the compound is black carbon charcoal. This phenomenon is observed when food or wood is burned to blackness. +1 or eat Possible Dehydration Intermediates (yellow to brown) + 2 's complexes (black) As paper (a cellulose product processed with acid) ages it slowly dehydrates and turns yellow. Scrapbookers prefer acid-free paper that will stay white longer. aramel candy is sugar that has been heated so as to partially dehydrate. Loss of some of the s from sugars results in a caramel brown color and also gives the characteristic taste of browned carbohydrates. A common method for making sauces and gravies uses the formation of a roux. Flour or starch is heated in oil until it browns. Water or milk is then added and the mixture heated to a thick sauce. The word roux is French for red and at some point in history came to mean flour that had been cooked long enough to change color. The fat and flour undergo browning reactions when cooked giving flavorful dehydrated molecules in much the same way as the caramelization process. The more the flour is browned the less power it has to thicken since some of the starch molecules shorten as well as dehydrate in the heating process. Therefore, more of a dark brown roux is needed to thicken a given amount of liquid than if using a pale roux. 106 Lab 22: arbohydrates (W16) 17

6 PREDURES: ATINS: PYSIAL PRPERTIES: I. Sweetness: 1. Taste a small sample of each sugar or sweetener available and rank them in order of sweetness. 1 (#1 being the sweetest.) 2. n the report sheet, record the predicted order 2 of sweetness from your textbook. ompare your taste results with the predicted order and report your observations. II. Absorption: 1. btain 5 inches (about 13 cm) of dialysis tubing. pen the tubing under a stream of tap water and then tightly tie one end of it closed with heavy thread. 2. Into the open end of the tubing pour 5 mls of a 1% starch solution. 3. To the tubing of starch now add 5 mls of 20% glucose solution and then tie the open end of the tubing tightly closed with heavy thread. 4. Under a gentle stream of tap water gently and quickly rinse off the outside of the filled tubing to remove any solutions that may have leaked or spilled during filling. NTES: 1 There will be a variety of results here as personal tastes vary. 2 The predicted order of sweetness varies somewhat by source but is generally as follows: Sweetener Sweetness Index Lactose 0.16 Maltose 0.33 Sorbitol 0.60 Glucose 0.75 Xylitol 1.00 Sucrose 1.00 Fructose 1.75 Aspartame 200 Stevia 300 Saccharin 400 Sucralose 600 Neotame 13,000 3 Dialysis Bag Set Up: 5. Tie both ends of the filled dialysis tubing to a stirring rod and suspend the bag 3 in a 150 ml beaker of warm 4 deionized water as shown. 6. Note the start time and allow the bag to remain in the water while you continue with the rest of the laboratory procedures (at least an hour if not more). 7. After at least 1 hour, remove the dialysis tubing, cut the string at one end, and pour the contents into a clean beaker. This is the inside sample. The water remaining in the 150 ml beaker will be the outside sample. Analysis: 8. btain 4 test tubes. Into 2 tubes put 1 ml of the inside sample (label In ) and into the other 2 tubes put 1 ml of the outside sample (label ut ) to test Test one inside sample and one outside sample for the presence of starch by adding 1 drop of I 2 /KI to each tube as in the iodine test for starch Part IV. 4 Warm to the touch (not hot) water will help the movement of sugars go faster. To maintain warmth you can place the beaker on a hot plate temporarily but on a very low setting. 5 You are testing to see if any starch or glucose passed through the dialysis tube into the beaker water. 10. Test the other inside sample and outside sample for the presence of glucose with the Benedict s test for reducing sugars in Part VI Lab 22: arbohydrates (W16)

7 III. Solubility: 1. btain 3 stoppered test tubes. Into tube #1 put a corn kernel sized scoop 6 of glucose (a monosaccharide). Into tube #2 put a corn kernel sized scoop of sucrose (a disaccharide). Into tube #3 put a corn kernel scoop of corn starch (a polysaccharide). 2. To each tube add 5 mls water. 7 Stopper and shake each tube to mix. Record the solubility of each on the report sheet If any of the samples are not completely soluble in cold water, warm their test tubes by letting them stand in hot water or carefully 9 over the flame of a laboratory burner. Record the solubility of each Save these samples for the Iodine test (Part IV). EMIAL REATIVITY: IV. Iodine, I 2,Test for Starch: 5. Take the 3 samples numbered #1 glucose, #2 sucrose, & #3 starch 10 that you used to test for solubility. 6. btain 3 more stoppered test tubes numbered #0, 4, and 5 and add 5 mls water to each of these. Perform the following: To tube #0 add nothing. Put it first in your line up of samples to use as the control. 11 To tube #4 add a corn kernel sized sample of the aspirin you prepared in the last lab experiment. To tube #5 add a corn kernel sized sample of solid crushed commercial aspirin tablet. 7. Into sample tubes #0-5 add 1 drop of Iodine-Potassium Iodide (I 2, KI) solution. Stopper and shake each to mix. bserve and record the color of all samples and make note of the presence of amylose ompare the results of the iodine test on the samples of acetylsalicylic acid and commercial aspirin. Make any conclusions as to the identity of the binder used in the commercial tablet. 13 V. ydrolysis of Starch: 1. btain 3 clean test tubes. Label 2 tubes A and B and into each of these tubes put about 2 mls of 1% starch solution. Into the third tube spit enough saliva (salivary amylase) to measure about 1 inch. 2. Pour the saliva into starch tube #B. Set tubes #A and #B aside for about 20 minutes or so. 6 Use the same size sample for each item so you can compare solubilities. 7 This measurement does not need to be exact. Make the first measurement with a graduated cylinder and then estimate the others by comparing the levels with that of the 1 st tube. 8 Record the solubility as S = soluble, I = insoluble, or 9 If heating with a flame, hold the tube with a wire test tube holder high in the flame just enough to warm it. Point the tube away from people. Avoid loss of water from heating. If water is lost add more to maintain 3 mls of solution. 10 This experiment could be done with starch in any form. rackers or bread crumbs also work. If using saltine crackers or dry bread, break off a pea sized piece and crush into a fine powder with a mortar and pestle before dissolving. In the absence of a mortar & pestle place the cracker in a square of waxed paper. Fold the waxed paper over the cracker and crush. 11 A control sample should show no reaction. We use it as a reference to which we can compare the others to tell if a reaction has taken place. 12 Iodine, I 2, turns dark blue if it complexes with the spiral form of amylose starch. 13 Starch (which is high in amylose) is often used in binders of commercial drug tablets. 14 Not all people have the same amount of amylase in their saliva. heck the results of other class members to see how their amylase reacted. 3. After about 20 minutes add 1 drop of Iodine, Potassium Iodide (I 2, KI) solution to each tube. 8 Stopper and shake each to mix. bserve and record the color note the presence of amylose Lab 22: arbohydrates (W16) 19

8 VI. Benedict s Test for Reducing Sugars: 1. Set up a boiling water bath by filling your largest beaker 1/4 th full of water and heating on a hot plate. 2. btain 6 clean test tubes and label them 1-6. Place 1 ml (or 20 drops) 6 of the following known carbohydrate samples into each of the tubes: Into tube #1 put 1 ml of deionized water as control samples. 11 Into tube #2 put 1 ml of 1% fructose. Into tube #3 put 1 ml of 1% glucose. Into tubes #4 put 1 ml of 1% sucrose. Into tubes #5 put 1 ml of 1% lactose. Into tubes #6 put 1 ml of 1% starch. 3. If the Part I, absorption test is completed place the inside ( In ) sample tube and the outside ( out ) sample tube saved from Part I in your line up of samples to test. If Part I test is not yet ready then go ahead with the known carbohydrate samples listed and test your in and out absorption test samples later in the same way. 4. To each sample tube add 3 ml of Benedict s reagent. 15 Stopper and shake each to mix. 5. Place tubes to be tested into the boiling water bath at the same time with the stoppers on very loosely so they do not pop off during heating. Remove the tubes after about 5 minutes and record any color changes. 6. n the report sheet circle the ion responsible for the color of each solution after the reaction is complete. Label each sample as reducing or nonreducing Report your conclusions. Explain any anomalies. 8. Dispose of the Benedict solutions in a designated waste container. VII. Dehydration: A. Dehydration with eat; aramelization: 1. btain two 250 ml beakers. Into one pour solid sucrose up to the 10 ml mark Into the other pour solid starch or flour about up to the 10 ml mark. 2. bserve the color, odor, chemical changes, etc. as you heat each sample over a hot plate or laboratory burner while stirring constantly. 17 Stop heating when the samples starts to turn caramel brown. Record all observations Return the beaker of caramelized sugar to the hot plate to continue the dehydration just until you have observed that the sugar is starting to turn black. Remove from heat and clean 19 the beaker. 15 Benedict s reagent is a solution of copper (II) sulfate in sodium hydroxide. 16 Benedict s reagent will react with any carbohydrate that can form a free aldehyde group in solution. These reducing sugars will reduce the blue u 2+ ions in the solution to produce red u 1+ ions instead. 17 Stirring constantly keeps the sugar from burning. 18 Notice any steam, water vapor, which may come from the reaction. The high heat forces the s and s to leave the carbohydrate as water. nce the s and s have left as water it is just the s, charcoal, which are left behind. 19 lean the beaker by boiling hot tap water in it until the burnt sugar is dissolved enough to be washed out. 20 oncentrated Sulfuric Acid is dangerous to your skin, eyes, and clothes. Do not breathe the vapors. Wash with copious amounts of water if contacted. 21 Wiping the con 2 S 4 from a dripping container would get the drop of acid you need on the paper towel. B. Dehydration with Acid: 1. Into a 50 ml beaker pour solid sucrose up to about the 25 ml mark. 2. Move the beaker of sucrose to the fume hood. Pour 10 mls concentrated Sulfuric Acid 20 onto the sucrose and observe the color, odor, and chemical changes. Record all observations. 3. Place a drop 21 of concentrated Sulfuric Acid on a piece of paper towel. Record your observations Lab 22: arbohydrates (W16)

9 VIII.PRATIAL APPLIATINS IN KING: (Instructor s hoice) A. Gak 1. Mix completely 2 level Tablespoons (about 30 mls) of cornstarch 22 with 1.5 teaspoons (7.5 mls) of water in a small beaker. Pour this mixture into your hands and play with the results of this Gak and describe its texture on the report sheet. 23 B. ornstarch/water Thickening Method: (Gravy) 2. In a separate beaker, heat ½ cup (120 mls) of water 24 (or broth). 3. With constant stirring, pour the corn starch gak 25 made in Part VIIIA into the hot water and bring to a boil until smooth and bubbly (about 1 minute). 26 Describe your results on the report sheet.. Roux Thickening Method: (heese Sauce) 1. Melt 2 level Tablespoons of triglycerides (fat) 27 in a beaker over low heat stirring constantly. 2. Blend in 2 level Tablespoons of cornstarch 22 (and seasonings like salt, pepper, or dry mustard if making a real cheese sauce) ook over low heat, stirring until mixture is smooth and bubbly. The mixture turns roux 28 colored as the amylose dehydrates. 3. Remove from heat. Stir in ½ cup (120 mls) water (milk for a real cheese sauce) then stirring constantly, bring to a boil until smooth and bubbly (about 1 minute). (If really making a cheese sauce; blend in ½ cup cheese, cut up or grated. Stir until cheese is melted.) 4. Describe your results on the report sheet. 29 D. Preparation of aramel andy: (ptional) Various starches can be used as thickeners. ornstarch gives a more transparent sauce. Flour gives a cloudy sauce because it contains insoluble suspended proteins. 23 More water or starch may be added to reach the desired consistency. The gak should be cutable like a solid yet pourable like a liquid. If you pour the gak into your hand and squeeze it should crumble. 24 The liquid could be broth that would become gravy. Adding gak to a pot of boiled vegetables and meat will create a thick soup or stew. 25 If you add dry flour or starch to hot water - bonding will occur on the surface of the starch granules and your gravy will be lumpy. 26 You can vary the proportion of starch to liquid to make your gravy thinner or thicker. 27 Any fat can be used. Gravies can be made by adding flour to melted shortening, margarine, or butter or the fat left behind from cooked meats like hamburger, bacon, or sausage. 28 The word Roux is French for reddish brown. 29 An additional experiment could be done to compare a sauce made with flour to that made with cornstarch. 30 Find a recipe or make up one of your own. Be sure your method uses actual dehydration of sugar rather than some other more instant method. 106 Lab 22: arbohydrates (W16) 21

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11 LAB 22: ARBYDRATES: PRE LAB EXERISES: NAME DATE More than one answer may be required. Give all correct answers Which of the following are not carbohydrates? A. fructose. aspartame E. saccharin B. glucose D. cellulose F. sucrose The major component of paper is A. amylose B. cellulose. glucose D. cellulite What is most important in making a carbohydrate water soluble? A. The ratio of s relative to s in the structure. B. The ratio of s relative to s in the structure.. The ratio of s available to hydrogen bond with water relative to s in the structure. D. Monosaccharides are water soluble but the others are not. Seliwanoff s test is used to distinguish A. a ketose from an aldose. B. a monosaccharide from a disaccharide.. a monosaccharide from a polysaccharide D. a reducing sugar from a nonreducing sugar. Which of the following statements explains the basis for obtaining a positive Benedict s test? A. A secondary alcohol is being oxidized to form a ketone. B. A primary alcohol is being oxidized to form an aldehyde.. An aldehyde is being oxidized to form a carboxylic acid. D. A tertiary alcohol cannot be oxidized easily. When a dilute iodine solution is placed on a slice of bread, the solution turns dark blue because bread contains A. glucose B. sucrose. protein D. amylose Amylose differs from amylopectin in that A. Amylose is digestible by humans but amylopectin is not. B. Amylose is branched but amylopectin is a straight chain.. Amylopectin is branched but amylose is a straight chain. D. Amylose is a polymer of -D-glucose but amylopectin is a polymer of -Dglucose. 8. Why does a solution made of starch get thick when heated in water? A. Granules of starch uncoil to give long strands that tangle into a gel. B. Starch granules stack in an organized pattern that makes the mixture solid.. Starch is insoluble so just forms complexes of suspended solids which thicken the mixture. 106 Lab 22: arbohydrates (W16) 23

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13 LAB 22: ARBYDRATES: REPRT: NAME PARTNER DATE I. Sweetness: Rank in order of sweetness from 1-6 (#1 being the most sweet) Fructose Glucose Sucrose Aspartame Sucralose Saccharin Stevia rder of Sweetness (Your Taste) rder of Sweetness (From literature) ompare your taste w/ literature: II. Absorption: Iodine Test (for starch) Benedict s Test (for glucose) bservations/results: bservations/results: Solution inside tubing Starch is Present or Not Present Glucose is Present or Not Present Solution outside tubing bservations/results: bservations/results: Explanation/Analysis: Explain why (give reasons for) your results. Explain any anomalies. Starch is Present or Not Present Glucose is Present or Not Present 1. The dialysis tubing used to test absorption in Part II represents what part of the body? A. the stomach B. the lungs. the intestines D. the throat 2. Why is it necessary that starch food be hydrolyzed in digestion rather than left in polymeric form? III. Solubility: 1. Glucose 2. Sucrose 3. Starch Solubility cold hot cold hot cold hot Explanation/Analysis: Explain /give reasons for the results. Explain any anomalies. n the given structure of glucose, show how water molecules hydrogen bond to all possible locations: Draw in more water molecules or draw in different orientation if you need to. 106 Lab 22: arbohydrates (W16) 25

14 EMIAL REATIVITY: IV. Iodine Test, I 2, for Starch bservation (olor w/ I 2) onclusion (Amylose present?) 0. ontrol 1. Glucose 2. Sucrose 3. Starch 4. Acetylsalicylic Acid olor olor olor olor olor olor Amylose? Amylose? Amylose? Yes or No Yes or No Yes or No Explanation/Analysis: Why did these results occur? Explain any Anomalies. Amylose? Yes or No Amylose? Yes or No 5. ommercial Aspirin Amylose? Yes or No V. ydrolysis: bservation At ~20 min onclusion (Is amylose present after reaction with amylase?) A. Starch olor w/ I 2 olor w/ I 2 Amylose? Yes or No Explanation/Analysis: Explain these results? Explain any Anomalies. B. Starch With Amylase Amylose? Yes or No 4. Why does the blue color of Iodine disappear when amylose reacts with saliva? A. Amylase in saliva causes the amylose chain to uncoil so Iodine is no longer trapped. B. Amylase in saliva reacts with iodine causing it to be unable to complex with the amylose coil.. Amylase in saliva causes the amylose chain to break into short chains and then into glucose which does not coil and so does not trap iodine. D. Amylase in saliva will replace the I 2 in the amylose coil and so remove the color. VI. Benedict s Test: 1. ontrol 2. Fructose 3. Glucose 4. Sucrose 5. Lactose 6. Starch olor after eating w/ Benedict s Ion produced u 2+ or u 2+ or u 2+ or u 2+ or u 1+ u 1+ u 1+ u 1+ Sugar Type Reducing Reducing Reducing Reducing or or or or nonreducing nonreducing nonreducing nonreducing Explanation/Analysis: Why did these results occur as they did? Explain any Anomalies. u 2+ or u 1+ Reducing or nonreducing u 2+ or u 1+ Reducing or nonreducing Lab 22: arbohydrates (W16)

15 1. Show the equation for the reaction between lactose (show structures) and Benedict s reagent. 2. Sucrose is a nonreducing sugar because A. it makes a person gain weight B. it does not contain a hemiacetal group. it is a monosaccharide D. it is a disaccharide VII. Dehydration with eat and Acid: eat on Sucrose eat on Starch When making a roux Acid on Sucrose Acid on ellulose bservations for Each Show the reaction of partial caramelization of sucrose: (Show any potential product). General Explanation for All What is happening in all of these cases and why? heat or The gaseous substance that is driven off of sucrose when it is heated is A. 2 B. S 3. 4 D. 2 The gaseous substance that is driven off of sucrose when it is reacted with acid is A. 2 B. S 3. 4 D. 2 The black residue left over after complete dehydration of a carbohydrate is A. B. S 3. S 2 D. 2 VIII. PRATIAL APPLIATINS IN KING: bservations, Results Explanation/Analysis A. Gak B. ornstarch/water Thickening Method (Gravy) n a separate page write a summary report explaining your observations and comparing the starch/water vs roux methods of thickening.. Roux Thickening Method (heese Sauce) D. aramel n a separate page write a summary report explaining your observations and explanation for the caramelization of sugar. 106 Lab 22: arbohydrates (W16) 27

16 LAB 22: ARBYDRATES: RELATED EXERISES: More than one answer may be correct. List all answers that apply Glucose ( ) is soluble in water but is not soluble in hexane ( 6 14 ) because A. compounds that have many s have polarity that attracts polar water but repels nonpolar hexane. B. compounds that contain oxygen will repel compounds that don t.. hexane is an organic solvent and glucose is not an organic compound. D. glucose has fewer hydrogens than hexane. ellulose is essential in human nutrition because A. it is undigestible so remains as long strands that act as fiber. B. it can be hydrolysed to form glucose which will be used as blood sugar.. it is undigestible and so acts as filler in food products so we can avoid calories. D. it can be digested to form glucose which will be used as blood sugar. Why do crackers and toast have the potential to taste sweet after chewing in your mouth? A. Amylose is naturally sweet tasting. B. Amylose reacts with amylase in saliva and produces glucose which tastes sweet.. Amylose reacts with sucrase and produces sweet tasting sucrose. If you had performed a Seliwanoff s test on sucrose the resulting product would have been red. Why does sucrose turn red with Seliwanoff s reagent? A. Sucrose is a ketose B. Sucrose is an aldose. Sucrose hydrolyses in the acidic Seliwanoff reagent to produce a ketose which then reacts to turn red. D. Sucrose hydrolyses in the acidic Seliwanoff reagent to produce an aldose which then reacts to turn red. Which carbohydrate(s) would you expect to produce both a reddish-orange solid with Benedict s and a red color with Seliwanoff s reagent? A. Fructose B. Glucose. Sucrose D. Lactose E. Amylose Which carbohydrate(s) would give both a color change with Benedict s and a light pink-orange color with Seliwanoff s reagent? A. Fructose B. Glucose. Sucrose D. Lactose E. Amylose Which carbohydrate(s) would not produce a color change with Benedict s, would produce a light pinkorange color with Seliwanoff s reagent, and would turn a blue-black color with iodine reagent? A. Fructose B. Glucose. Sucrose D. Lactose E. Amylose 8. Why do infant formulas often contain mixes of dextrins and maltose rather than starch? Lab 22: arbohydrates (W16)