Acetyl Coa & Tca Cycle

The correct answer is the oxidative decarboxylation of pyruvate to CO2 and acetyl CoA. The pyruvate dehydrogenase complex is responsible for converting pyruvate, a product of glycolysis, into acetyl CoA, which is a crucial molecule in the citric acid cycle. This process involves the removal of a carboxyl group from pyruvate, resulting in the release of CO2, and the remaining acetyl group is transferred to Coenzyme A (CoA) to form acetyl CoA. This reaction generates high-energy electrons that are captured by NAD+ to produce NADH, which can then be used in oxidative phosphorylation to generate ATP.

Catabolic action refers to the breakdown of complex molecules into simpler ones. This process releases energy, which is stored in high energy metabolites. These metabolites, such as ATP, can be used by the cell for various energy-requiring processes. Additionally, catabolic action also produces new materials like amino acids and porphyrins, which can be used for the synthesis of proteins and other essential molecules in the cell.

ATP and NADH inhibit key steps of the TCA cycle. ATP is a high-energy molecule that is produced during cellular respiration and is used as a source of energy for various cellular processes. When ATP levels are high, it indicates that the cell has sufficient energy and can inhibit the TCA cycle to prevent excessive production of ATP. NADH, on the other hand, is an electron carrier molecule that is generated during the breakdown of glucose. High levels of NADH indicate that the cell has sufficient energy and can also inhibit the TCA cycle to prevent excessive production of NADH.

Succinate dehydrogenase is complex II of the mitochondrial electron transport chain. It is responsible for transferring electrons from succinate to ubiquinone, which is a crucial step in the production of ATP. This enzyme is embedded in the inner mitochondrial membrane and plays a key role in the oxidation of succinate, a substrate derived from the citric acid cycle.

When 1 mole of pyruvate is converted into acetyl-CoA, it produces 1 mole of NADH. This is because during the conversion process, one molecule of NAD+ is reduced to NADH. Therefore, the correct answer is 1.

Molecules with proximal thiols, such as dihydrolipoamide, are targets for covalent modification by arsenite. This means that arsenite can form a covalent bond with the proximal thiols in dihydrolipoamide, leading to a chemical modification of the molecule. Proximal thiols are sulfur-containing groups that are located close to the active site of the molecule, making them susceptible to interaction with arsenite. This interaction can have various effects on the function and structure of the molecule, potentially leading to biological consequences.

The TCA cycle is considered to be anapleurotic because there are multiple points around the cycle where reactants can enter. This means that the cycle can be replenished with intermediates from other metabolic pathways, ensuring a constant supply of reactants for energy production. This flexibility allows the TCA cycle to adapt to changing metabolic demands and maintain its function as a central hub in cellular metabolism.

Coenzyme A and lipoamide are the acyl group carriers in the pyruvate dehydrogenase complex. Coenzyme A carries the acetyl group, while lipoamide carries the other acyl groups, such as the succinyl and propionyl groups. FAD and NAD+ are electron carriers, and TPP (thiamine pyrophosphate) is a coenzyme involved in decarboxylation reactions. Therefore, the correct answer is Coenzyme A and lipoamide.

Thiamine pyrophosphate, lipoamide, and flavin adenine dinucleotide are permanently bound cofactors in the pyruvate dehydrogenase reaction. This means that they are tightly bound to the enzyme and participate in the reaction without being released or consumed. These cofactors play essential roles in catalyzing the conversion of pyruvate to acetyl-CoA, which is an important step in cellular respiration. Thiamine pyrophosphate is involved in decarboxylation reactions, lipoamide acts as a carrier of acetyl groups, and flavin adenine dinucleotide is a redox cofactor.

When there is an excess of ATP and NADH, the citric acid cycle (also known as the Krebs cycle) slows down. Acetyl CoA, α-ketoglutarate, and succinyl-CoA are all intermediates in the citric acid cycle, which means they are produced and consumed during the cycle. However, when there is an excess of ATP and NADH, the cycle slows down and fewer intermediates are formed. Therefore, Acetyl CoA, α-ketoglutarate, and succinyl-CoA are not formed in sufficient quantities when there is an excess of ATP and NADH.