Question

Which of the following is released during conversion of succinate to fumarate in TCA cycle?
(a) CO₂
(b) FADH₂
(c) H₂O
(d) ATP

Answer 1

Which of the following is released during conversion of succinate to fumarate in TCA cycle?

(a) CO₂

(b) FADH₂✔✔✔

(c) H₂O

(d) ATP

Answer:- FADH₂

Answer 2

Answer:

Succinate and fumarate are the intermediates of TCA cycle. When succinate is converted to fumarate, 2 protons are removed which are taken by FAD and convert into FADH2. This reaction is catalysed by succinate dehydrogenase.

Explanation:

• The Krebs cycle, also known as the TCA cycle or the citric acid cycle, is a series of enzyme-catalyzed reactions that take place in the mitochondrial matrix and involve the oxidation of acetyl-CoA to produce carbon dioxide and the reduction of coenzymes to produce ATP for the electron transport chain. Hans Krebs proposed the intricate cycle, which earned it the name Krebs cycle. In 1953, he received the Nobel prize for his work. The acetyl group of acetyl-CoA is oxidised to make two molecules of CO2 in a succession of eight steps, while also producing one ATP. Additionally, reduced high-energy molecules like NADH and FADH2 are created.
• Each glucose molecule yields two acetyl-CoA molecules, resulting in two Krebs cycle spins.

Krebs Cycle Phases

• It involves eight steps. In the matrix of mitochondria, the Krebs cycle or TCA cycle occurs in aerobic conditions.
• Step 1: Coenzyme A is released during the condensation of acetyl CoA with the 4-carbon molecule oxaloacetate to create 6C citrate. Citrate synthase is the catalyst for the process.
• Step 2: Isocitrate, the isomer of citrate, is produced. This process is catalysed by the enzyme aconitase.
• Isocitrate is dehydrogenated and decarboxylated in step 3 to produce 5C -ketoglutarate. The emission of CO2 in a molecular form. The process is catalysed by isocitrate dehydrogenase. It is an enzyme that depends on NAD+. NADH is created from NAD+.
• In step 4, succinyl CoA, a 4C molecule, is created by the oxidative decarboxylation of -ketoglutarate. The enzyme complex known as -ketoglutarate dehydrogenase facilitates the process. NAD+ is changed to NADH, which results in the emission of one CO2 molecule.
• Step 5: Succinate is created by succinyl CoA. The process is catalysed by the succinyl CoA synthase enzyme. Along with that, GDP is phosphorylated at the substrate level to produce GTP. ATP is created when GTP transfers its phosphate to ADP.
• In step 6, the enzyme succinate dehydrogenase converts succinate to fumarate. As a result, FAD is changed into FADH2.
• Step 7: By adding one H2O, fumarate is transformed into malate. Fumarase is the enzyme that is catalysing this reaction.
• Step 8: Malate is dehydrogenated to form oxaloacetate, which combines with another molecule of acetyl CoA and starts the new cycle. Hydrogens removed, get transferred to NAD+ forming NADH. Malate dehydrogenase catalyses the reaction.