Essay About Iodine Test And 2Ml

Testing for Macromolecules
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Testing for Macromolecules Surina Dulat 20669629Partner: Umeira Vijendr 20672777T.A: Jeannette Lam, Vivian Tan Section 015BIOL 130LLab Section date: October 5, 2016 2:30pm Date of experiment: September 28, 2016 Introduction The objective of this lab is to determine the macromolecule(s) present in each solution and use that information to identify the macromolecules(s) present in the unknown solution. Many living organisms are composed of atoms that are linked together to make larger molecules known as macromolecules. The different types of macromolecules are carbohydrates, proteins, lipids, and nucleic acids. Starch and glycogen are carbohydrates. Therefore, to test for them in solutions, the Iodine test is performed. The test consists of adding 1 drop of iodine solution to each sample and waiting for the solutions to change to either a blue-black colour to indicate starch is present or a reddish-brown colour to indicate that glycogen is present (Bates, French, Rundle, 1943, p. 142). Similarly, when testing for proteins, the Biuret test is used. To test for protein in the solutions, 2mL of 10% sodium hydroxide solution and 5 drops of 1% copper sulfate is added to each solution and the colour change is observed (Bhandary, Kumari N., Bhat, K.P, Bekal, 2012, p. 36). If the solution changes to a violet colour, it indicates protein is present (Bhandary et al, 2012, p. 36).  In the Benedict’s test, 2mL of Benedict’s solution is added to each solution and the contents are boiled for 5 minutes each then observed for colour change ranging from yellow to green or red to brown for a positive result (Bhandary et al, 2012, p. 36). There are positive and negative results that occur in each test. A positive test result means that the experiment has worked according to your hypothesis while a negative test result means that the experiment’s substance that is being tested has not changed (Andreoni, 1995). Materials and MethodsPlease refer to pages 20-24 of the fall 2016 BIOL 130l manual for material and methods for this la. All steps founded without any deviations (Department of Biology, 2016). Observation and Results Table 1: Iodine Test for starch and glycogen Test tube number Before colour change Positive/negative reaction After colour change 115ml of 1% glucose solution (clear)Negative Yellow 215ml of 0.3% glucose-1-phosphate (clear) NegativeYellow315ml of 1% maltose solution (clear) NegativeYellow415ml of honey solution (yellow)NegativeYellow515ml of 1% sucrose solution (clear)NegativeYellow615ml of 1% lactose solution (clear)NegativeYellow715ml of 1% glycogen solution (clear)Positive Reddish-brown (glycogen present)815ml of 1% starch solution (clear) Positive Blue-black (starch present)915ml of protein (clear)NegativeYellow1015ml of beer (clear) NegativeYellow1115ml of distilled water (clear)NegativeYellow1215ml of unknown #72 solution (clear) Positive Blue-black (starch present) The table is the result of the Iodine test which was used to test for starch and glycogen in each solution. Most of the solutions produced negative results except for test tubes #7, 8, and 12. The solutions in test tubes #7, 8 and 12 changed colour therefore they produced positive results. Test tube #8 and #12 turned a blue-black colour to indicate that starch is present while test tube #7 turned reddish-brown to indicate that glycogen is present. In starch, the polymer amylose reacted with the iodine solution which produces the blue colour (Bates et al, 1943, p.143). Since glycogen is very branched compare to starch, therefore, the branched polymer amylopectin reacted with the iodine solution to produce the reddish-brown colour (Bates et al, 1943, p.142).  Table 2: Benedict’s test for reducing sugars Test tube number Colour before reaction  Positive/negative reaction  Colour change after 5 minutes of reaction 115ml of 1% glucose solution (clear)Positive Reddish-brown 215ml of 0.3% glucose-1-phosphate (clear) Negative Blue 315ml of 1% maltose solution (clear) Positive Brown 415ml of honey solution (yellow)Positive Orange-red 515ml of 1% sucrose solution (clear)Negative Blue 615ml of 1% lactose solution (clear)NegativeBlue (after another 5 minutes, the result was positive and colour was reddish-brown)715ml of 1% glycogen solution (clear)NegativeBlue 815ml of 1% starch solution (clear) NegativeBlue 915ml of protein (clear)NegativeBlue 1015ml of beer (clear) Positive Green 1115ml of distilled water (clear)NegativeBlue 1215ml of unknown #72 solution (clear) NegativeBlue (extra 5 minutes, still blue therefore negative result) This table shows the results of the Benedict’s test which was used to test for reducing sugars which are sugars that have free aldehyde group (Alberts, Bray, Hopkin, Johnson, Lewis, Raff, Roberts, Walter, 2014, p.53).  The reducing sugars in the solution react with the benedict’s solution to produce colours from yellow or green to red or brown. Most test tubes tested negative while some tested positive.