Recitation_8-handout-Simona

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

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: TA: Simona Tescu 7.05 Recitation 8 email: tescu@mit.edu 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: tescu@mit.edu 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: tescu@mit.edu 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: tescu@mit.edu 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: tescu@mit.edu Glycogen synthesis Hexokinase Mutase 4/9/08 Glucose -------> Glucose 6-P -----> Glucose 1-P 5/9 TA: Simona Tescu 7.05 Recitation 8 email: tescu@mit.edu 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: tescu@mit.edu 4/9/08 7/9 TA: Simona Tescu 7.05 Recitation 8 email: tescu@mit.edu 4/9/08 8/9 TA: Simona Tescu 7.05 Recitation 8 email: tescu@mit.edu 4/9/08 9/9 ...
View Full Document

Ask a homework question - tutors are online