Recitation_8-handout-Simona - TA: Simona Tescu 7.05...

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Unformatted text preview: TA: Simona Tescu 7.05 Recitation 8 email: RECITATION #8 Today we will cover: Lecture 20, 21, 22 (some 23) • • • • • • Simple carbohydrates: nomenclature and examples Disaccharides and polysaccharides: examples High energy compounds: PEP Glycolysis Glycogen hydrolysis glucose Glycogen synthesis 4/9/08 At the end of these 3 lectures you should know the following mechanisms: • Aldolase reaction (forward and reverse) • Isomerase reaction • Mutase reaction • Oxidative phosporylation reaction (+ NAD structure) Carbohydrates: Nomenclature and examples (CH2O)n , n=(3 to 7) o n=3: triose o n=6: hexose Aldose vs ketose D vs L carbohydrates o D carbohydrates have the OH of the last chiral carbon on the right 5 vs 6 member rings (most stable ring structures) o 5 – furan ring o 6 – pyran ring Alpha and beta forms (at equilibrium: 2/3 beta and 1/3 alpha) o Alpha – OH below the ring o Beta – OH above the ring Fischer projection Haworth (ring) projection o OH’s to the left – above the ring o OH’s to the right – below the ring Reducing (acetal) vs non-reducing (hemiacetal) α/β OH o Pyranose vs pyranoside o Furanose vs furanoside Name: Alpha (or beta) --- L (or D) --- sugar name + 5 or 6 ring name (furanosyl or pyranosyl) --X>Y (#carbon involved in the intra-saccharides bond) --- pyranose/ oside or furanose/ oside 1/9 TA: Simona Tescu 7.05 Recitation 8 email: Questions: 1. Draw an isomer of glucose. Draw an epimer of glucose. 2. Draw the Howarth projections of D-glucose and D-Fructose. 3. 4/9/08 4. (Exam 3, 1999) Draw the structure of the following compound: β–D–galactopyranosyl–(12)–α–D–manopyranosyl–(12)–β–D– fructofuranoside 5. Explain the Fehling diagnostic test for sugars. 6. (2004 pset 7) Give the mechanism for the following reaction, starting and ending with the sugars in their closed-ring forms: Glucose-6-P <---> Fructose-6-P 7. (2005 pset 6) D-glucose is incubated in 3H labeled water along with an isomerase enzyme which catalyzes the transformation of D-glucose <---> D-fructose. In which positions will 3H be found in glucose? Show the mechanism of incorporation. Examples of disaccharadies and polysaccharides • lactose (handout) • sucrose (handout) • maltose (handout) • • • amylose: α-D-glucospyranosyl units bound 1 4, with a reducing end amylopectin: α-D-glucospyranosyl units bound 1 4 and 1 6 a. branch points – every 25-30 glucose units glycogen: α-D-glucospyranosyl units bound 1 4 and 1 6 b. glucose storage found in animals c. branch points every 10-15 units hyaluronic acid chitin: N-acetyl glucosamine units bound in β 14 linkage • • 2/9 TA: Simona Tescu 7.05 Recitation 8 email: High energy compounds • acetyl phosphate • thioesthers • ATP • Phosphocreatine • Phospho-enol pyruvate (PEP) Question 8: Why is PEP such a highly energetic compound? Glycolysis: START MAKING YOUR CHART! 1 glucose 2 lactate 4/9/08 KNOW: All steps and enzymes Aldolase mechanism – forward and reverse NAD structure and mechanism of oxidative phosphorylation What steps are reversible and what steps are irreversible! Net NAD utilization in glycolysis = 0 Net “visible”ATP production = 2 • Anaerobic glycolysis 2 ATP • Aerobic glycolysis 6 ATP (2NAD+ are oxidized to 2NADH by the electron transport chain….we’ll learn later in the course….) Question 9. 3/9 TA: Simona Tescu 7.05 Recitation 8 email: Question 10. 4/9/08 Assume the hypothetical compound below can be converted to two 3-carbon compounds by the action of a single enzyme of the type described in class. What would the products be? You need not show the mechanism of this transformation. Question 11. 4/9 TA: Simona Tescu 7.05 Recitation 8 email: Glycogen synthesis Hexokinase Mutase 4/9/08 Glucose -------> Glucose 6-P -----> Glucose 1-P 5/9 TA: Simona Tescu 7.05 Recitation 8 email: Glycogen hydrolysis: generation of glucose 4/9/08 Phosphatase Glucose-6-P Questions 12. ------ > Glucose Question 13. Explain why arsenate is a poison. 6/9 TA: Simona Tescu 7.05 Recitation 8 email: 4/9/08 7/9 TA: Simona Tescu 7.05 Recitation 8 email: 4/9/08 8/9 TA: Simona Tescu 7.05 Recitation 8 email: 4/9/08 9/9 ...
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