All of the following products of biosynthesis are nitrogen-rich tetrapyrrole structures that can be synthesized from Krebs cycle intermediates (in some plants, animals, or bacteria), with the exception of:triglyceride moleculeschlorophyll b moleculesvitamin B12 moleculeschlorophyll a moleculesheme molecules Identify the Krebs cycle enzyme that consumes a six-carbon substrate molecule, producing a five-carbon product molecule along with NADH, and one molecule of CO2.succinyl CoA synthetasea-ketoglutarate dehydrogenasemalate dehydrogenaseisocitrate dehydrogenasecitrate synthase

Citric acid cycle or Krebs Cycle is the cyclic metabolic pathway for the oxidation of various intermediates compounds molecules like amino acids, fatty acids, and carbohydrates. It occurs in mitochondria. It is amphibolic in nature. It starts with the condensation of acetyl COA with oxaloacetate to form citrate. According to the question, the following five tetrapyrrole structures are given Triglyceride molecules Chlorophyll a and b molecules Vitamin B12 heme moleculesTriglycerides Triglycerides are the esters of glycerol and fatty acid. Fatty acids are the long-chain carboxylic acid. Fatty acids are synthesized from acetyl CoA which is an intermediate in the citric acid cycle. Chlorophyll a and b are synthesized from glutamate which can be converted to ketoglutarate by transamination. Ketoglutarate is a citric acid cycle intermediate. Vitamin B12 It is a tetrapyrrole but it is not synthesized from citric acid cycle intermediate. It is not found in plant sources, available only in animal food sources. It is synthesized by microorganisms in the intestine of animals. It is the only molecule that has cobalt in it. hence it is also called cobalamin. It is known as an Anti-pernicious factor. Heme molecules It is a tetrapyrrole that is synthesized from Succinyl COA which is an intermediate of citric acid cycle. During the biosynthesis of heme, succinyl COA condensed with glycine, and the reaction needs coenzyme PLP (Pyridoxal Phosphate for the stability of carbanion intermediate. Final Answer: Hence out of the five given tetrapyrroles, Vitamin B12 is not synthesized from citric acid cycle intermediate whereas others are synthesized from TCA cycle intermediate as given in the table. Tetrapyrrole TCA cycle intermediate used for synthesis Triglyceride Acetyl CoA Chlorophyll a and b Glutamate to Ketoglutarate (Through transamination) Heme Succinyl COAFive enzymes of TCA are given Succinyl CoA synthase Catalyzes the conversion of succinyl CoA into succinate Succinyl CoA is a 5 carbon compound and succinate is 4 carbon compound In this reaction, only GTP is formed. In this reaction, neither NADH is formed nor CO2 is released. Ketoglutarate dehydrogenase It catalyzes the oxidative decarboxylation of Ketoglutarate. NADH and CO2 are formed. Ketoglutarate is a 5-carbon compound, not 6 carbon. Malate dehydrogenase catalyzes the dehydrogenation of malate to oxaloacetate malate and oxaloacetate are 4 carbon compound. CO2 is not released although NADH is formed in this reaction. Isocitrate dehydrogenase catalyzes the oxidative decarboxylation of Isocitrate to Ketoglutarate NADH and CO2 are formed. Isocitrate is 6 -carbon compound and Ketoglutarate is a 5-carbon compound citrate synthase condenses oxaloacetate and acetyl CoA into citrate oxaloacetate is a 4-carbon compound and citrate is a 6-carbon compound. NADH and CO2 are not formed.Out of the given five enzymes, the Krebs cycle enzyme that consumes a six-carbon substrate molecule, producing a five-carbon product molecule along with NADH, and one molecule of CO2 is Isocitrate dehydrogenase catalyzes the oxidative decarboxylation of Isocitrate to Ketoglutarate NADH and CO2 are formed. Isocitrate is 6 -carbon compound and Ketoglutarate is a 5-carbon compound