A & P I Lab – WS 3
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reagent
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A chemical agent used to bring about a chemical reaction (color change)
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enzyme
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any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions
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Benedict's Test
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tests for presents of reducing sugars (monosaccharides and disaccharides); reagent must be boiled to make the color change (aprox 15 mins); poison (Cooper Sulfate)
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Benedict's Test - Positive Results
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solution changes: blue to green (disaccharide), yellow, orange or red (monosaccharide)
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Iodine (IKI) Test
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tests for the presence of starch
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Iodine (IKI) Test - Positive Results
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instantaneous color change to dark brown-black or bluish-black as iodine is trapped in large starch molecule; poison
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Buiret Test
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tests for peptides polymers or amino acids; color intensity is proportional to the number of peptide bonds (length of the molecules) present; poison and corrosive
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Buiret Test - Positive Results
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protein & large polypeptides = violet or purple; shorter peptides (oligopeptides, dipeptides, amino acids) = pink color
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Brown Paper Test
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tests for lipids; lipids do not evaporate; drop on a brown paper bag makes an oily spot if absent, drop evaporates
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Benedict's Test - Negative Results
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Blue (no mono- or disaccharides present)
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Iodine (IKI) Test - Negative Results
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pale-dark yellow (no starch present)
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Buiret Test - Negative Results
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Blue (no peptide polymers or amino acids present)
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Evaporation Test
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aqueous solutions will evaporate while oil will not
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Evaporation Test - Negative Results
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evaporation occurs (aqueous solution = no oil)
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Evaporation Test - Positive Results
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no evaporation, lipids present and often spread out on brown paper
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Tween 20 Test
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breaks oils into smaller lipid droplets (easier to digest)
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Tween 20 Test - Negative Results
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no layer or droplet formation
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Tween 20 Test - Positive Results
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Lipids separate out as smaller droplets in water or forms layer on water; surrounds & breaks up lipids
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Amylase
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enzyme that breaks down plant starch into disaccharides
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Pepsin
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breaks down protein into smaller peptides in the stomach
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Protein Test Results (Sample + Biuret)
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Positive Results: Whole Milk, Skim Milk & 100% egg white
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Results from Protein Test (Sample + Pepsin + .2% HCl + Biuret)
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Positive Results: Whole Milk, Skim Milk & 100% egg white
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Carbohydrate Test: Sample + IKI
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Positive Results: Corn Syrup, Corn Starch & Potato Slice
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Sugar Test Results (Sample + Benedicts)
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Monosaccharides: Whole Milk, Skim Milk, Chicken Broth, Corn Syrup, Honey, Onion Juice; Disaccharides: Honey, Nectress, Potato Juice
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Carbohydrate Function Test Results
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Starch + Amylase + Benidicts = positive; Starch + Pepsin + .2% HCl + Benidicts = negative
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Results from Brown Paper/Lipid Test
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No Evaporation: Vegetable Oil, Whole Milk, Skim Milk
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Solubility/Emulsification Test Results
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Positive Results: Water & Oil (no Tween - separate layers), Veg. Oil + water + Tween (oil droplets and bubbles), Whole Milk (2 layers) & skim milk (slight layering)
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Tween 20
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bile salt; when mixed with oil & water, breaks up oil into smaller droplets
