where is atp produced in citric acid cycle

Question

Majdolin · Accepted Answer

ATP production in the citric acid cycle is an indirect process. The citric acid cycle itself doesn't directly generate ATP molecules.

The citric acid cycle harvests energy from breaking down glucose. It does this by capturing the energy released in chemical reactions through the formation of high-energy electron carriers:

NADH (nicotinamide adenine dinucleotide, reduced)
FADH2 (flavin adenine dinucleotide, reduced)

The real site of ATP production is the electron transport chain (ETC). This chain is located in the inner mitochondrial membrane (separate from the citric acid cycle in the matrix). The ETC uses the high-energy electrons from NADH and FADH2 to generate a proton gradient across the membrane.

The proton gradient powers ATP synthase, an enzyme also embedded in the inner mitochondrial membrane. This enzyme harnesses the energy stored in the proton gradient to produce ATP molecules through a process called chemiosmosis.

These electron carriers don't store usable cellular energy (ATP) themselves. They simply carry the potential for energy production.

TEOFILA · Answer

ATP production in the citric acid cycle is indirect. The citric acid cycle itself doesn't directly generate ATP molecules. Instead, it prepares the stage for ATP production through a later process called oxidative phosphorylation.

Carolinne · Answer

In the citric acid cycle (also known as the Krebs cycle or tricarboxylic acid cycle), ATP is produced through substrate-level phosphorylation at two specific steps: during the conversion of succinyl-CoA to succinate and during the conversion of phosphoenolpyruvate to pyruvate.

Conversion of Succinyl-CoA to Succinate: In this step, which occurs in the enzyme-catalyzed reaction of succinyl-CoA synthetase, a molecule of GTP is synthesized directly by substrate-level phosphorylation. GTP can then be converted to ATP in a subsequent step by nucleoside diphosphate kinase.

Conversion of Phosphoenolpyruvate to Pyruvate: Although not directly within the citric acid cycle itself, pyruvate can enter the cycle and be converted to ATP.

XUAN · Answer

In the citric acid cycle (also known as the Krebs cycle or TCA cycle), ATP is primarily produced through substrate-level phosphorylation. This occurs in two main steps:

Succinyl-CoA Synthetase Reaction: During the conversion of succinyl-CoA to succinate, a molecule of ATP is generated. This is a direct substrate-level phosphorylation where a high-energy phosphate group is transferred from succinyl-CoA to ADP, forming ATP.

GTP Formation: In some organisms or tissues, the enzyme succinyl-CoA synthetase can alternatively produce GTP instead of ATP during the same step. GTP can subsequently be converted to ATP.

These reactions take place in the mitochondrial matrix, where the citric acid cycle enzymes are located. The citric acid cycle itself is a central metabolic pathway that oxidizes acetyl-CoA derived from carbohydrates, fats, and proteins to produce energy in the form of ATP and reducing equivalents (NADH and FADH2).

Overall, the ATP production in the citric acid cycle occurs through substrate-level phosphorylation during the conversion of succinyl-CoA to succinate (generating ATP or GTP depending on the organism), contributing directly to cellular energy production.