• Experiments, lab manual and powerpoint ACC Organic Molecules of Life • All living cells contain and produce four different types of organic molecules. They are often referred to as molecules of life. The four molecules of life are carbohydrates, protein, lipids and nucleic acid (DNA). Carbohydrates are polymers of monosaccharides, proteins are polymers of amino acids, DNA is a polymer of nucleotides. Lipids can be hydrolyzed to fatty acids and glycerol. • Qualitative assay, shows whether a particular substance is present, but does not give an indication of how much is present. Use chemical indicators • Chemical indicator: changes its own color in presence of a specific substance Carbohydrates (C,H,O ratio 1:2:1) • Monosaccharides the monomers for carbohydrates are aldehydes and ketones. Aldehydes have terminal carbonyl (C=O) group, while ketones have interior C=O group. Glucose • • Fructose When hexose (6 carbon sugars) dissolved in water they can exist in two forms, linear and ring. C=O the functional group exist in the linear form of the monosaccharide. Reducing sugars: • Any sugar that possesses a C=O group is capable of donating electron to a weak oxidizing agent • Such sugars are called reducing sugars • Oxidation (e loss) Reduction (e gain) • All monosaccharides are reducing sugars. Why? • Some disaccharides are reducing sugars. Why? Mono and disaccharides • Benedict’s assay (negative light blue, positive green/red) 2+ • Cooper ion of Benedict’s is reduced from cupric (Cu ) to cuprous (Cu+ ). • Copper then binds to oxygen to form copper oxide (Cu2 O), which is green/red. Experiment 500 ul; 1% 1 Glucose 2 3 Lactose Fructose 4 5 6 Galactose Maltose Starch 7 Water 5 ml Benedict Boil all tubes for 5 minutes Remove the tubes and score each tube as positive or negative in the results table (page 49) Results, table 5.1 page 49 Monosaccharides • Chemical indicator is Barfoed’s (negative light blue, positive green/red) • Is set to acidic pH (~4.5). In acidic environment The reducing disaccharide can’t reduce the cupric ion (Barfoed’s), but the monosaccharide can • Oxidation-reduction reaction Experiment 500 ul; 1% 1 Glucose 2 3 Lactose Fructose 4 5 6 Galactose Maltose Starch 7 Water 500 ul Barfoed Boil all tubes for 5 minutes Remove the tubes and score each tube as positive or negative in the results table (page 49) Results, table 5.1 page 49 Polysaccharides • Starch; chemical indicator is iodine Experiment 500 ul; 1% 1 Glucose 2 3 Lactose Fructose 4 5 6 Galactose Maltose Starch 7 Water 3 drops iodine Remove the tubes and score each tube as positive or negative in the results table (page 49) Results, table 5.1 page 49 Lipids • Composed of atoms of C, H and O. They ae hydrophobic and made of fatty acids and glycerol. They are used as secondary source of energy (ATP). • Miscibility test: negative miscibility test refers to no mixing of liquids. This indicated the presence of hydrophobic substance such as lipids • Chemical indicator is Sudan black, it will give positive miscibility results with lipids Experiment 3ml 1 Oil 2 Sucrose 3 Starch 4 Water 3ml water Mix record miscibility results (page 49) 15 drops Sudan Black Mix record miscibility results (page 49) Results, table 5.1 page 49 Protein • • • • Proteins are polymers composed of amino acids and contain atoms of C, H, O, N and S. In proteins amino acids are linked by peptide bonds. Chemical indicator is Biuret test. Blue negative and violet/purple positive It detects peptide bonds. • Biuret, is copper sulfate dissolved in strong alkaline solution. • Denature proteins and expose primary structure • Copper sulfate reacts with exposed peptide bonds causing the violet or purple color 1 2 3 4 Experiment 15 drops Biuret 1 drop Egg albumin Glucose Starch Water Enter the results in the table page 50 Results, page 50 Benedict’s assay Barfoed’s assay - Iodine + Biuret • Experiments, lab manual and powerpoint ACC Organic Molecules of Life • All living cells contain and produce four different types of organic molecules. They are often referred to as molecules of life. The four molecules of life are carbohydrates, protein, lipids and nucleic acid (DNA). Carbohydrates are polymers of monosaccharides, proteins are polymers of amino acids, DNA is a polymer of nucleotides. Lipids can be hydrolyzed to fatty acids and glycerol. • Qualitative assay, shows whether a particular substance is present, but does not give an indication of how much is present. Use chemical indicators • Chemical indicator: changes its own color in presence of a specific substance Carbohydrates (C,H,O ratio 1:2:1) • Monosaccharides the monomers for carbohydrates are aldehydes and ketones. Aldehydes have terminal carbonyl (C=O) group, while ketones have interior C=O group. Glucose • • Fructose When hexose (6 carbon sugars) dissolved in water they can exist in two forms, linear and ring. C=O the functional group exist in the linear form of the monosaccharide. Reducing sugars: • Any sugar that possesses a C=O group is capable of donating electron to a weak oxidizing agent • Such sugars are called reducing sugars • Oxidation (e loss) Reduction (e gain) • All monosaccharides are reducing sugars. Why? • Some disaccharides are reducing sugars. Why? Mono and disaccharides • Benedict’s assay (negative light blue, positive green/red) 2+ • Cooper ion of Benedict’s is reduced from cupric (Cu ) to cuprous (Cu+ ). • Copper then binds to oxygen to form copper oxide (Cu2 O), which is green/red. Experiment 500 ul; 1% 1 Glucose 2 3 Lactose Fructose 4 5 6 Galactose Maltose Starch 7 Water 5 ml Benedict Boil all tubes for 5 minutes Remove the tubes and score each tube as positive or negative in the results table (page 49) Results, table 5.1 page 49 Monosaccharides • Chemical indicator is Barfoed’s (negative light blue, positive green/red) • Is set to acidic pH (~4.5). In acidic environment The reducing disaccharide can’t reduce the cupric ion (Barfoed’s), but the monosaccharide can • Oxidation-reduction reaction Experiment 500 ul; 1% 1 Glucose 2 3 Lactose Fructose 4 5 6 Galactose Maltose Starch 7 Water 500 ul Barfoed Boil all tubes for 5 minutes Remove the tubes and score each tube as positive or negative in the results table (page 49) Results, table 5.1 page 49 Polysaccharides • Starch; chemical indicator is iodine Experiment 500 ul; 1% 1 Glucose 2 3 Lactose Fructose 4 5 6 Galactose Maltose Starch 7 Water 3 drops iodine Remove the tubes and score each tube as positive or negative in the results table (page 49) Results, table 5.1 page 49 Lipids • Composed of atoms of C, H and O. They ae hydrophobic and made of fatty acids and glycerol. They are used as secondary source of energy (ATP). • Miscibility test: negative miscibility test refers to no mixing of liquids. This indicated the presence of hydrophobic substance such as lipids • Chemical indicator is Sudan black, it will give positive miscibility results with lipids Experiment 3ml 1 Oil 2 Sucrose 3 Starch 4 Water 3ml water Mix record miscibility results (page 49) 15 drops Sudan Black Mix record miscibility results (page 49) Results, table 5.1 page 49 Protein • • • • Proteins are polymers composed of amino acids and contain atoms of C, H, O, N and S. In proteins amino acids are linked by peptide bonds. Chemical indicator is Biuret test. Blue negative and violet/purple positive It detects peptide bonds. • Biuret, is copper sulfate dissolved in strong alkaline solution. • Denature proteins and expose primary structure • Copper sulfate reacts with exposed peptide bonds causing the violet or purple color 1 2 3 4 Experiment 15 drops Biuret 1 drop Egg albumin Glucose Starch Water Enter the results in the table page 50 Results, page 50 Benedict’s assay Barfoed’s assay - Iodine + Biuret Biology 115 Lab Fall 2018 Lab 5 Worksheet Instructors: _____________________________________________________________________________________ I. Student Name: Group Members: _____________________________________________________________________________________ II. Personalized Title [0.5 pts] _____________________________________________________________________________________ III. Hypothesis [1.0 pts] 1. _____________________________________________________________________________________ IV. Introduction IVA. General Theory/Background [1.0 pts] IVB. Summary of Overall Approach [1.5 pts] Page 1 of 3 Biology 115 Lab Fall 2018 Lab 5 Worksheet Instructors: _____________________________________________________________________________________ V. Observations & Results VA. Data [1.5 pts] VB. Calculations [0.5 pts] Page 2 of 3 Biology 115 Lab Fall 2018 Lab 5 Worksheet Instructors: VI. Discussion Questions 1. What is a reducing sugar? Which functional group associated with reducing sugars? 0.5 pt 2. If a carbohydrate gives positive Benedict’s assay results, can you predict the Barfoed assay results? Explain your answer. 0.5 pt 3. If you completely hydrolize a lipid what would you produce? 0.5 pt Page 3 of 3 
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