Lab Practical Study Guide - Lab Practical Study Guide Lab...

Lab Practical Study Guide
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Lab Practical Study Guide Lab 1: Macromolecules 4 classes of macromolecules: carbohydrates, proteins, lipids, and nucleic acids (monomers are monosaccharides, amino acids, fatty acids, nucleotides) Exercise 1: Carbohydrates : made of C, H, and O o Monosaccharides include glucose, fructose, galactose, ribose o Disaccharides Maltose = glucose + glucose Lactose = glucose + galactose Sucrose = glucose + fructose o Polysaccharides include starch (energy storage in plants), cellulose (structural), and glycogen (energy storage in animals) Starch is used for storing glucose in plants that was created by photosynthesis. Examples of food containing starch are potatoes and root veggies. It is a polymer of glucose with α 1-4 glycosidic bond (linear amylose) and the occasional α 1-6 bond (branched amylopectin) Cellulose is composed of β 1-4 glycosidic linkages o Activity A Benedict’s test (detects monosaccharides and disaccharides—but not sucrose ) Positive: colored precipitate (yellow, green, orange, or red) Negative: clear blue Must be mixed with a substance and then heated in boiling water to yield a result When mixed with glucose, it forms a red precipitate (positive) Limitations of these tests are that they are qualitative, not quantitative (don’t tell us any information about how concentrated the substance is) o Activity B Iodine test : mix a few drops of I2KI solution with the sample (detects starch) Positive: dark blue Negative: yellow o Acticity C Hydrolysis : a chemical reaction used to break down polymers; a chemical bond is cleaved by the addition of H2O Two different experiments were run: hydrolysis of sucrose (Sucrose + HCl) and hydrolysis of starch (Starch + HCl) Sucrose hydrolyzes (into glucose and fructose) much faster than starch hydrolyzes, because starch is a polysaccharide Exercise 2: Lipids : diverse class of hydrophobic molecules o Fatty acids are primary made of carbon and hydrogen o Can be structural (membrane lipids) or store energy (triacylglycerols, sterols, vitamins) o Can be saturated (all single bonds—solid at room temp) or unsaturated (at least one double bond—liquid at room temp) o Energy storages molecules store ATP (seeds, adipose tissue) o Paper test : if it is transparent, there are lipids present. If it is opaque, there are no lipids present. Oil tested positive. Exercise 3: Proteins : a polymer of amino acids linked by a peptide bond
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o There are about 20 different amino acids o Biuret test detects peptide bonds: add to sample and wait for color change. Positive: pink (smaller proteins) or violet (larger proteins) Negative: blue Exercise 4: Macromolecules in food o Activity A: Separation of butter Butter is an emulsion : the lipids occur in very small droplets dispersed throughout the water-soluble portion (carbs and proteins) Clarification : the lipid is separated from the water-soluble protein part (used for
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