Concept explainers
(a)
Interpretation:
HMG-CoA is encountered in the process (1) glycerol
Concept introduction:
Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.
The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.
Ketogenesis is a metabolic process by which
Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.
After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to
(a)
Answer to Problem 25.104EP
HMG-CoA is encountered in ketogenesis.
Explanation of Solution
HMG-CoA is produced in step 2 in ketogenesis.
Step 2 is a condensation reaction. In step 2, acetoacetyl CoA reacts with acetyl CoA and water to produce 3-hydroxyl-3-methylglutaryl (HMG-CoA) and CoA-SH. The reaction for step 2 is:
(b)
Interpretation:
NADPH is encountered in the process (1) glycerol metabolism to dihydroxyacetone phosphate, (2) β-oxidation pathway, (3) ketogenesis, and (4) lipogenesis has to be identified.
Concept introduction:
Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.
The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.
Ketogenesis is a metabolic process by which ketone bodies are produced by the breakdown of fatty acids and ketogenic amino acids. This metabolic process supplies our organs with needed energy under certain circumstances such as starvation. Fatty acid molecules degrade into acetyl CoA which are utilized as reactants in the process of ketogenesis. These molecules of acetyl CoA undergo the process of condensation twice, followed by chain cleavage and hydrogenation to produce ketone bodies.
Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.
After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to
(b)
Answer to Problem 25.104EP
NADPH is encountered in lipogenesis.
Explanation of Solution
NADPH acts as the reducing agent in step 2 and 4 of the cyclic process of lipogenesis. NADPH gets oxidized to form NADP+.
Step 2 involves the hydrogenation of acetoacetyl ACP to synthesis β-hydroxybutyrylwith the help of reducing agent NADPH. The reaction of this step is:
Step 4 again involves hydrogenation reaction. In this step, crotonyl ACP is converted to butyryl ACP with the help of reducing agent NADPH. The reaction of this step is:
(c)
Interpretation:
Malonyl ACP is encountered in the process (1) glycerol metabolism to dihydroxyacetone phosphate, (2) β-oxidation pathway, (3) ketogenesis, and (4) lipogenesis has to be identified.
Concept introduction:
Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.
The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.
Ketogenesis is a metabolic process by which ketone bodies are produced by the breakdown of fatty acids and ketogenic amino acids. This metabolic process supplies our organs with needed energy under certain circumstances such as starvation. Fatty acid molecules degrade into acetyl CoA which are utilized as reactants in the process of ketogenesis. These molecules of acetyl CoA undergo the process of condensation twice, followed by chain cleavage and hydrogenation to produce ketone bodies.
Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.
After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to
(c)
Answer to Problem 25.104EP
Malonyl ACP is encountered in lipogenesis.
Explanation of Solution
Malonyl ACP is the reactant in step 1 in the cyclic process in lipogenesis.
The first step involves the condensation reaction between acetyl ACP and malonyl ACP. The product formed in the first reaction is acetoacetyl ACP. The reaction of step 1 is:
(d)
Interpretation:
Acetoacetyl CoA is encountered in the process (1) glycerol metabolism to dihydroxyacetone phosphate, (2) β-oxidation pathway, (3) ketogenesis, and (4) lipogenesis has to be identified.
Concept introduction:
Lipogenesis is the process employed for the synthesis of fatty acid. The starting precursor for the synthesis is acetyl CoA. The enzyme employed for the process is fatty acid synthase. It is a multienzyme complex that ties the reaction responsible for the synthesis of fatty acid. The fatty acid is synthesized in two parts. In the first part, there is citrate-malate shuttle system and in the second part, there is a cyclic process to synthesize saturated fatty acid.
The fatty acids are broken down to provide energy. The breakdown of fatty acids is a three parts process. In the first part, the fatty acid is activated. In the second part, the transportation of fatty acid into the mitochondrial matrix is facilitated by a shuttle mechanism. In the third part, the fatty acid is readily oxidized, cycling through a series of four reactions. In these series of reactions, acyl CoA is degraded to acetyl CoA. This pathway is termed as β-oxidation pathway.
Ketogenesis is a metabolic process by which ketone bodies are produced by the breakdown of fatty acids and ketogenic amino acids. This metabolic process supplies our organs with needed energy under certain circumstances such as starvation. Fatty acid molecules degrade into acetyl CoA which are utilized as reactants in the process of ketogenesis. These molecules of acetyl CoA undergo the process of condensation twice, followed by chain cleavage and hydrogenation to produce ketone bodies.
Triacylglycerol mobilization is an ongoing process in which triacylglycerols that are stored in the adipose tissue are hydrolyzed. Fatty acids and glycerol are the products of triacylglycerol mobilization. The products are released into the bloodstream.
After entering the bloodstream, the glycerol travels to the kidneys or liver. The first stage of glycerol metabolism occurs in the liver or kidney where it is converted to
(d)
Answer to Problem 25.104EP
Acetoacetyl CoA is encountered in ketogenesis.
Explanation of Solution
Step 2 is a condensation reaction. In step 2, acetoacetyl CoA reacts with acetyl CoA and water to produce 3-hydroxyl-3-methylglutaryl (HMG-CoA) and CoA-SH. The reaction for step 2 is:
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Chapter 25 Solutions
EBK GENERAL, ORGANIC, AND BIOLOGICAL CH
- When one acetyl CoA is processed through the citric acid cycle, how many times does each of the following events occur? a. A FAD molecule is a reactant. b. A CoA-SH molecule is produced. c. A dehydrogenase enzyme is needed for the reaction to occur. d. A C5 molecule is produced.arrow_forwardWhich of the following enzymes possesses a catalytic mechanism extremely similar to that of the Pyruvate Dehydrogenase Complex? A. the isocitrate dehydrogenase B. the succinate dehydrogenase C. the alpha-ketoglutarate dehydrogenase D. the malate dehydrogenasearrow_forwardWhich of the following is the chemical end product of fatty-acids metabolized in the beta-oxidation pathway? Select one: a. Beta-carotine b. Free-radicals c. Lactic acid d. Acetyl-CoA e. Pyruvatearrow_forward
- Which of the following statements about the "central role" of TCA is/are correct? a. Some metabolic intermediates of TCA are used as non-carbohydrate sources for gluconeogenesis. b. β-oxidation of lipids produces acetyl-CoA that can enter TCA. c. All metabolic intermediates in TCA are used in the biosynthesis of amino acids. d. Degraded amino acids are converted to metabolic intermediates of TCA, then to ketone bodies.arrow_forwardWhich of the following citric acid cycle enzymes catalyzes substrate-level phosphorylation? A) isocitrate dehydrogenase B) α-ketoglutarate dehydrogenase C) succinyl CoA synthetase D) succinate dehydrogenase E) malate dehydrogenasearrow_forwardConsider the reactions of ketogenesis. (a) What role does acetyl-CoA play?(b) How many acetyl-CoA molecules are used in the production of the ketonebodies?(c) What is the essential role of ketone bodies during prolonged starvation?arrow_forward
- alpha-ketoglutarate dehydrogenase will do which of the following: Select one: a. Pyruvate is decarboxylated to become acetyl-CoA producing NADH and Carbon dioxide b. Succinate is oxidized to become fumarate forming FADH2 c. Succinyl-CoA becomes Succinate and forms one ATP molecule and Coenzyme A-SH d. Oxaloacetate combines with the acetyl from acetyl-CoA to produce Citric acid(citrate) e. Malate is oxidized to become oxaloacetate forming NADH f. Isocitrate and then decarboxylated and oxidized to produce alpha-ketoglutarate, Carbon dioxide and NADH g. Citrate is rearranged to become Isocitrate h. Fumarate is combined with water to become Malate i. alpha-ketoglutarate is oxidized and decarboxylated to produce Succinyl-CoA, Carbon dioxide and NADHarrow_forwardIf a fatty acid containing 13 carbons is subjected to Beta oxidation, how many molecules of Acetyl CoA can be produced?arrow_forwardPlace the following list of reactions or relevant locations in the β oxidation of fatty acids in the proper order. (a) Reaction with carnitine (b) Fatty acid in the cytoplasm (c) Activation of fatty acid by joining to CoA (d) Hydration (e) NAD+ -linked oxidation (f) Thiolysis (g) Acyl CoA in mitochondrion (h) FAD-linked oxidation.arrow_forward
- What enzyme is inhibited by the group of medications known as statins? a)HMG-CoA synthase b)Aromatase c)Fatty acid synthase d)Cyclooxygenasearrow_forwardThe sources of the three (3) carbons in malonyl-Coa is/are: a. 1 C from C02 and 2 C from acetyl-CoA b. 1 C from HCO3- and 2 C from acetyl-CoA c. 1 C from biotin and 2 C from acetyl-CoA d. All three C from acetyl-CoAarrow_forwardThe rate-limiting step in fatty acid synthesis is: a. The reduction of the acetoacetyl group to a ?-hydroxybutyryl group b. Formation of malonyl-CoA from malonate and coenzyme A. c. Condensation of acetyl-CoA and malonyl-CoA. d. The reaction catalyzed by acetyl-CoA carboxylase.arrow_forward
- BiochemistryBiochemistryISBN:9781305577206Author:Reginald H. Garrett, Charles M. GrishamPublisher:Cengage Learning