1. Consider the fermentation pathways of Clostridium as diagrammed on the next page. A metabolism has been optimized to make acetic acid, butyric acid, and another product (in addition to the product gas stream containing hydrogen and carbon dioxide). The feed substrate is glucose ($C_6H_{12}O_6$) and the yields are 0.5 mole of acetic acid ($C_2H_4O_2$) per mole of glucose and 0.5 mole of butyrate ($C_4H_8O_2$) per mole of glucose. Hint: the pathway should preserve a balanced redox state (NAD+/NADH ratio). A. What is the other product and what is its yield from glucose? B. Write a balanced chemical reaction for this metabolism starting with 2 moles of glucose. Hint: another potential reactant/product is water, which participates in some of the reactions diagrammed on the next page though it is not explicitly shown. Water is not the answer to part A.
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KREBS CYCLE The 2 moles of pyruvic acid produced per molecule of glucose from glycolysis in the cytoplasm enter the mitochondria successively. Initial Reaction: pyruvic acid + CoA-SH (coenzyme A) + NAD+ to produce acetyl-CoA + CO2 + NADH + H+ ion as products. In the initial reaction, considering the products in the conversion of pyruvic acid to acetyl-CoA, aside from the condensation reaction of pyruvic acid with CoA-SH, what is the other reaction involved? In Step 1, how many carbon atoms are there in citric acid? What reactions between acetyl-CoA and oxaloacetic acid are involved in forming citric acid? In Steps 2 and 3, what are the reactions involved in forming isocitric acid? In Steps 4 and 5, the conversion of isocitric to α-ketoglutaric acid uses NAD+ to produce NADH and CO2. What are the reactions involved? Compare the number of carbon atoms between isocitric and α-ketoglutaric acid. In Step 6, the conversion of α-ketoglutaric acid to succinyl CoA requires the removal of CO2 using NAD+ and CoA-SH to produce NADH and succinyl-CoA. What reactions are involved in producing succinyl-CoA? Compare the number of carbon atoms between α-ketoglutaric acid and succinyl CoA. In Step 7, 1 mole of ATP is produced in the conversion of succinyl-CoA to succinic acid. What reactions are involved? In Step 8, the conversion of succinic to fumaric acid uses FAD (same role as NAD+). What reaction is involved? Identify the change in the functional group. In Step 9, the conversion of fumaric to malic acid, what reaction is involved? In Step 10, the conversion of malic to oxaloacetic acid uses NAD+. What is the reaction involved? Identify the change in the functional group. Account for the sum total of ATP produced from glycolysis and Krebs cycle.
Dominador T.
What is the net yield of ATP from the complete oxidation of one pyruvate molecule to CO2 and H2O? List the metabolic pathways used. The net yield is two ATPs per glucose molecule. The remaining 34 molecules of ATP generated during the complete aerobic metabolism of glucose are synthesized during oxidation of pyruvate to CO2 and H2O in mitochondria. Metabolic pathway of oxidation of pyruvate - A carboxyl group is snipped off of pyruvate and released as a molecule of carbon dioxide, leaving behind a two-carbon molecule (out of the six originally present in glucose). - The two-carbon molecule from step 1 is oxidized, and the electrons lost in the oxidation are picked up by NAD+ to form NADH (2 NADH from NAD+). - The oxidized two-carbon molecule is attached to Coenzyme A to carry the acetyl group to the citric acid cycle. - In the citric acid cycle, acetyl CoA joins with a four-carbon molecule, oxaloacetate, releasing the CoA group and forming a six-carbon molecule called citrate. - Citrate is converted into its isomer, isocitrate. - Isocitrate is oxidized and releases a molecule of carbon dioxide, leaving behind a five-carbon molecule, α-ketoglutarate. - The remaining four-carbon molecule picks up Coenzyme A, forming the unstable compound succinyl CoA. - The CoA of succinyl CoA is replaced by a phosphate group, which is then transferred to ADP to make ATP. The four-carbon molecule produced in this step is called succinate. - Succinate is oxidized, forming another four-carbon molecule called fumarate. - Water is added to the four-carbon molecule fumarate, converting it into another four-carbon molecule called malate. The citric acid cycle is a series of reactions that produces two carbon dioxide molecules, one GTP/ATP, and reduced forms of NADH and FADH2.
Adi S.
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