BCMB 3100 final Exam quizzes and answers

1. Recognize and describe the structure of important dietary carbohydrates including ribose, glucose, mannose, fructose, galactose, sucrose, lactose, glycogen, starch and cellulose - -ribose is not an isomer because it only has 5 carbons -what type of isomer are they? • Glucose and mannose: epimers at carbon 5 • Galactose and glucose are diastereomers • Fructose vs. glucose are constitutional isomers • Alpha glucose has a hydroxyl group that is pointing down -Glycogen, Starch, and Cellulose are storage forms of glucose -cellulose joined by B-1,4 linkages giving it high tensile strength and the ability to form long chains. Forms structures in plants. -glycogen and starch are formed by a-1,4 linkages (with some a-1,6) which give it a hollow helix. This allows it to be a very accessible store of sugar. - Sucrose and Lactose are Disaccharides 2. List the major functions of carbohydrates. - • Providing energy and regulation of blood glucose. • Sparing the use of proteins for energy. • Breakdown of fatty acids and preventing ketosis. • Biological recognition processes. • Flavor and Sweeteners. • Dietary fiber 3. Describe how carbohydrates are digested and how they are absorbed in the intestines and the bloodstream - 1) large molecules are broken down into smaller units. This is digestion. All large molecules are hydrolyzed and broken into smaller, more manageable pieces, which are monosaccharides. The SGLT transporter is how these monosaccharides are absorbed into the intestinal cells. 2) These small molecules are degraded into a few simple units that play a central role in metabolism: sugars, fatty acids, glycerol, and other amino acids. Converted to acetyl CoA. Small ATP release 3) ATP is produced from the complete oxidation of acetyl CoA: consists of the citric acid cycle and oxidative phosphorylation. 4) The SGLT transporter is how these monosaccharides are absorbed into the intestinal cells 5) The GLUT transporter is how these carbs are absorbed into the blood stream. -Catabolic reactions: reactions that transform fuels into cellular energy. -Anabolic reactions: reactions that require energy. Useful forms of energy produced in catabolism are employed in anabolism to generate complex structures. 4. Describe the reaction catalyzed by the enzyme lactase and list the symptoms observed in individuals that lack lactase activity. - -Lactase cleaves the glycosidic bond formed in disaccharides, forming glucose and galactose - Without lactase, lactose remains in small intestine and is broken down by bacteria instead and that bacteria releases gas, etc, that cause stomach problems - Symptoms include diarrhea, stomach cramps, bloating, and gas -Located in small intestine 5. Outline why milk alternatives and the use of Lactaid with dairy intake do not cause symptoms in lactose intolerant individuals. - -Other milk alternatives do not have lactose, and therefore would not need the lactase enzyme to break anything down