For each turn of the Krebs cycle

For each turn of the Krebs cycle:
a) How many ATP are produced?
b) How many NADH are produced?
c) How many FADH, are produced?
d) How many molecules of carbon dioxide are produced?

The correct answer and explanation is :

Answers for Each Turn of the Krebs Cycle:

a) ATP Produced: 1 ATP (or GTP, depending on the cell type)
b) NADH Produced: 3 NADH
c) FADH₂ Produced: 1 FADH₂
d) CO₂ Produced: 2 CO₂

Explanation:

The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a crucial metabolic pathway that occurs in the mitochondrial matrix. It plays a key role in cellular respiration by oxidizing acetyl-CoA to generate high-energy molecules used in ATP production.

Each turn of the Krebs cycle begins when a two-carbon acetyl-CoA molecule combines with a four-carbon oxaloacetate to form a six-carbon compound, citrate. Through a series of enzyme-catalyzed reactions, citrate is progressively broken down, regenerating oxaloacetate and producing important energy-carrying molecules.

1. ATP (or GTP) Production:
   ATP (or GTP in some cells) is generated through substrate-level phosphorylation in the conversion of succinyl-CoA to succinate. This step directly yields 1 ATP per turn of the cycle.
2. NADH Production:
   During the oxidation of isocitrate, α-ketoglutarate, and malate, electrons are transferred to NAD⁺, forming 3 NADH per turn. These NADH molecules will later contribute to ATP generation through the electron transport chain.
3. FADH₂ Production:
   During the conversion of succinate to fumarate, electrons are transferred to FAD, forming 1 FADH₂ per turn. Like NADH, FADH₂ donates electrons to the electron transport chain for ATP synthesis.
4. CO₂ Production:
   Decarboxylation reactions occur during the conversion of isocitrate to α-ketoglutarate and α-ketoglutarate to succinyl-CoA, releasing 2 CO₂ molecules per turn as waste products of glucose metabolism.

Since one glucose molecule generates two acetyl-CoA molecules, the Krebs cycle turns twice per glucose, effectively doubling these values for total ATP yield.