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Identification of Carbohydrates ,Lipids,and Proteins lab

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´╗┐Introduction ________________ Identification of Carbohydrates ? Investigation 2 Background: Carbohydrates are composed of only the elements Carbon, Hydrogen, and Oxygen, and all carbohydrates have the same empirical formula: (C H O). They provide a source of energy to all cells. Plants manufacture their carbohydrates through the process of photosynthesis. Animals need carbohydrates to function, but they cannot produce any on their own, therefore, they have to consume plants, or an animal that eats plants to receive their share. In this experiment, we use Benedict?s solution to detect certain carbohydrates called ?reducing sugars? in the materials. The free aldehyde groups of the reducing sugars are oxidized by the metallic ion found in Benedict?s solution. If a substance does contain ?reducing sugars? then the reaction results in the formation if a coloured precipitate. We also use iodine to detect the presence of starch and glycogen. Iodine solution reacts with the starch producing a purple black color. It also reacts with glycogen to produce a more brown color. Purpose: The purpose of this experiment is to determine the types of carbohydrates that are found in various foods. Independent variables: The materials tested (1% glucose, 1% fructose, etc.) Dependant variables: The colour change of the materials Controlled variables: Volume of materials tested, volume of Benedict?s solution added, volume of iodine added Control Sample: Distilled water Lipid Identification ? Investigation 3 Background: Lipids contain Carbon, Hydrogen, and Oxygen and make up fats, oils, and waxes. ...read more.


Clear brown 10% Corn Syrup Yellow/Clear Darker, clear orange Skim Milk Murky White White murky yellow, color doesn?t dissolve Carrot Extract Murky Orange Clear brown Celery Extract Light clear green Clear orange Potato Extract Murky brown Black-brown peach color Distilled Water Clear Clear orange yellow Investigation 3: Lipid Identification ? a) Translucence test Materials Observations When Holding Paper Up To Light Peanuts Spotted translucent spots, paper is spotted in a type of oil Butter Large translucent spot Lean Meat Small translucent spot in middle, paper stained red Lard Large clear translucent spot Vegetable Oil Large very clear translucent spot Skim Milk Paper isn?t that translucent Whole Milk More translucent than skim, still not very translucent Distilled Water Translucent (40%) Ethanol Barely translucent (7%) Sudan N. Paper isn?t translucent but it?s stained red Investigation 3: Lipid Identification ? b) Emulsion test Materials Observations Under Microscope Butter Bubbles (small) seen, lipids seen + fat (clump) Lard Bubbles small, spreading out, no fats Peanuts Bubbles small, lipids seen + fat Lean Meat No lipids, but bubbles seen Investigation 3: Lipid Identification ? c) Sudan IV test Materials Sudan Dissolves in: Skim Milk, Whole Milk, Vegetable Oil Investigation 4: Identification of Proteins ? a) Biuret test Materials Colour before adding NaOH and CuSO4 then shaking Colour after adding NaOH and CuSO4 then shaking 10% egg albumin Clear Violet (deep purple); purple doesn?t diffuse easily, stays on top 1% Gelatin Clear Even deeper violet; purple doesn?t diffuse easily, stays on top Milk White Blue, then light purple (after shaking) ...read more.


To improve this experiment, the procedure should state that water should be added to a point where the test tubes are three quarters submerged. In the Emulsion test, the crushing of the solid ingredients was a very messy task. When crushing a solid in a mortar, you had to add ethanol. The solids were very difficult to mash, and the liquids kept spilling over. If you mashed too hard, it would spill, but it you didn?t grind as hard, the solids would remain solids for ages. To improve this experiment, I would suggest using a smaller sample of solids and liquids. I would reduce the amount from 3 grams to 1.5 grams (of solids) and I would reduce the amount of ethanol used from 10mL to 5mL. In the end of the experiment, only one drop of the liquid I required, so reducing the sample size makes a lot of sense During the Sudan IV test, we had to ?shake the mixture vigorously?. This was a problem because Sudan IV is corrosive and touching it would be potentially dangerous. The instructions don?t specify a safe way to shake the test tubes. I would suggest that the instructions include that you use a test tube stopper to prevent the corrosive solution from spilling. Conclusion The only ingredient tested in experiment one that didn?t contain carbohydrates is distilled water. The ingredients that don?t contain lipids are ethanol, Sudan IV and distilled water. The ingredients that don?t contain proteins are distilled water. ...read more.

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