Concept explainers
(a)
Interpretation: To determine the number of NADH molecules formed during one turn of the citric acid cycle.
Concept introduction: Citric acid cycle is the third stage of the biochemical energy production process. The cycle includes the reactions in which the acetyl part of acetyl CoA is oxidized and leads to the formation of carbon dioxide and
(a)
Answer to Problem 23.70EP
Three molecules of NADH are formed in step 3, 4 and 8 of the citric acid cycle.
Explanation of Solution
Step 3 is the first step where both the oxidation and decarboxylation occurs. Step 3 involves the oxidation of isocitrate and formation of CO2. In this step, firstly isocitrate is oxidized by
Step 4 involves the oxidation of
Step 8 is an oxidation reaction and the last step of the citric acid cycle. In step 8,
The reaction of step 8 is:
Hence, three molecules of NADH are formed in the citric acid cycle.
(b)
Interpretation: To determine the number of GTP molecules formed during one turn of the citric acid cycle.
Concept introduction: Citric acid cycle is the third stage of the biochemical energy production process. The cycle includes the reactions in which the acetyl part of acetyl CoA is oxidized and leads to the formation of carbon dioxide and
(b)
Answer to Problem 23.70EP
One molecule of GTP is formed in step 5 of the citric acid cycle.
Explanation of Solution
Step 5 involves the thioester bond cleavage in
(c)
Interpretation: To determine the number of time decarboxylation reactions occur during one turn of the citric acid cycle.
Concept introduction: Citric acid cycle is the third stage of the biochemical energy production process. The cycle includes the reactions in which the acetyl part of acetyl CoA is oxidized and leads to the formation of carbon dioxide and
(c)
Answer to Problem 23.70EP
Decarboxylation occurs twice in the citric acid cycle in step 3 and 4.
Explanation of Solution
Step 3 is the first step where both the oxidation and decarboxylation occurs. Step 3 involves the oxidation of isocitrate and formation of CO2. In this step, firstly isocitrate is oxidized by
The final product is
Step 4 involves the oxidation of
The final product is
(d)
Interpretation: To determine the number of time oxidation-reduction reaction occur during one turn of the citric acid cycle.
Concept introduction: Citric acid cycle is the third stage of the biochemical energy production process. The cycle includes the reactions in which the acetyl part of acetyl CoA is oxidized and leads to the formation of carbon dioxide and
An overview of the citric acid cycle is as follows:
(d)
Answer to Problem 23.70EP
The oxidation-reduction reaction occurs four times in the citric acid cycle in step 3, 4, 6 and 8.
Explanation of Solution
Step 3 is the first step where both the oxidation and decarboxylation occurs. Step 3 involves the oxidation of isocitrate and formation of CO2. In this step, firstly isocitrate is oxidized by
Step 4 involves the oxidation of
In step 6, oxidation of succinate occurs to form fumarate. The enzyme involved in this step of the citric acid cycle is succinate dehydrogenase. FAD is the oxidizing agent in this step. This reaction takes place in the inner mitochondrial membrane. The reaction of step 6 is:
Step 8 is an oxidation reaction and the last step of the citric acid cycle. In step 8,
The reaction of step 8 is:
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Chapter 23 Solutions
General, Organic, and Biological Chemistry
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- ATP is an ALLOSTERIC INHIBITOR of the phosphofructokinase enzyme, which is a key catalyst for one of the first steps of Glycolysis. Citrate (citric acid) is a 6-carbon product of the first reaction of the Krebs Cycle (aka Citric Acid Cycle). Interestingly, Citrate enhances the inhibitory effect of ATP on phosphofructokinase. What is a likely explanation for the inhibitory effects of these molecules? Excess ATP and Citrate signal the cell that Glycolysis should be speeded up. Excess ATP and Citrate signal a positive feedback loop. Excess ATP and Citrate signal the cell that Glycolysis should be slowed. Excess ATP and Citrate compete for the active site of phosphofructokinase.arrow_forwardWhat is the reduction potential (DE) for the reaction catalyzed by isocitrate dehydrogenase if the citric acid cycle is fluxing? To get the answer scored correctly: Please report the answer to three decimal places. Example: 0.123 or -0.111 Do not include units.arrow_forwardWhich of the following is the second step of Citric Acid Cycle? Select one: a. Isocitrate and then decarboxylated and oxidized to produce alpha-ketoglutarate, Carbon dioxide and NADH b. Succinyl-CoA becomes Succinate and forms one ATP molecule and Coenzyme A-SH c. alpha-ketoglutarate is oxidized and decarboxylated to produce Succinyl-CoA, Carbon dioxide and NADH d. Malate is oxidized to become oxaloacetate forming NADH e. Fumarate is combined with water to become Malate f. Citrate is rearranged to become Isocitrate g. Pyruvate is decarboxylated to become acetyl-CoA producing NADH and Carbon dioxide h. Oxaloacetate combines with the acetyl from acetyl-CoA to produce Citric acid(citrate) i. Succinate is oxidized to become fumarate forming FADH2arrow_forward
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