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BIO 2960 HW 6 - Problem Set#6 KEY Bio2960 Spring 2012 1 The...

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1 Problem Set #6 KEY Bio2960; Spring 2012 1. The teacher of Bio2960 did not ask you to memorize a whole lot of chemical structures. However, he wanted you to know the structures of glyceraldehyde 3- phosphate, pyruvate and acetyl CoA (not CoA though) because these intermediates are major metabolic crossroads in cellular metabolism. Draw the chemical structures of these compounds and list the biochemical pathways/processes that are linked to each of these compounds. Also, indicate the cellular compartments (in an eukaryotic cell) where these pathways/processes take place. [Name of sub-organelle compartments should be mentioned in your answer. Glyceraldehyde 3-phosphate Pyruvic acid (pyruvate) Acetyl CoA Glyceraldehyde 3 phosphate: glycolysis (cytosol), gluconeogenesis (cytosol), Calvin cycle (stroma [matrix] of chloroplasts), glycerol synthesis (cytosol). Pyruvate: glycolysis (cytosol), gluconeogenesis (cytosol), fermentation (cytosol), pyruvate oxidation (matrix of mitochondria), alanine synthesis (cytosol) Acetyl CoA: pyruvate oxidation (matrix of mitochondria), fatty acid degradation (matrix of mitochondria), fatty acid synthesis (cytosol), citric acid cycle (matrix of mitochondria), glyoxylate cycle (glyoxysomes in plants). 2. Based on the discussions we had in class, estimate how many ATP molecules are produced when one molecule of glucose is fully oxidized in CO 2 . How many ATP molecules are produced if oxygen supply is rather limited? The table below outlines accountings of the energy gain from the metabolism of a single glucose molecule.
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2 This scenario uses the figures cited in lecture (see PPT file): 2.5 ATPs per NADH and 1.5 ATPs per FADH 2 . Step Anaerobic (low oxygen) Aerobic (plenty of oxygen) Glycolysis ATP invested - 2 ATP - 2 ATP 2 cytoplasmic NADH (see below) ATP generated by substrate level phosphorylation + 4 ATP + 4 ATP Pyruvate Oxidation 2 mitochondrial NADH + 5 Oxidative Phosphorylation 6 mitochondrial NADH + 15 2 mitochondrial FADH 2 + 3 GTP generated by substrate-level phosphorylation + 2 GTP (ATP) 2 cytoplasmic NADH from glycolysis (whose electrons are shuttled into the mitochondria and donated to FADH 2 ) (because of the mitochondrial membranes being a physical barrier for the transport of NADH from cytosol to mitochondria) + 3 Total 2 30 3. Explain why most fatty acids contain even-numbered carbon chain. Because the building block of a fatty acid is the two-carbon acetyl CoA. 4. Based on the information/answer in Q2 above, try to figure out how many ATPs are generated if a molecule of palmate (16 carbons), a saturated fatty acid enriched in palm oil, is fully oxidized. One palmitate with 16 carbons can be cleaved 7 times by the β -oxidation process to generate 8 molecules of acetyl CoA, which will then further metabolized in the citric acid cycle. Initially, palmitate has to be converted to palmityl CoA consuming one molecule of ATP (of course, this steps requires one molecule of HS-CoA as well).
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