The number of ATPs generated in one turn of Krebs cycle are –
**Core Concept:** The Krebs cycle (also known as the Citric Acid Cycle or TCA cycle) is a crucial part of cellular respiration where organic molecules are broken down to produce ATP (Adenosine Triphosphate), NADH, and FADH2. The cycle consists of 10-12 enzymatic reactions that take place in the mitochondria.
**Why the Correct Answer is Right:** The correct answer is **C. 2**. In one turn of the Krebs cycle, two ATP molecules are generated. The process involves the oxidation of acetyl-CoA, which is derived from glucose or other organic molecules, and the reduction of NAD+ to NADH. This process produces energy in the form of ATP.
**Why Each Wrong Option is Incorrect:**
A. **2 ATP**: This option is incorrect because the Krebs cycle generates two ATP molecules per turn, not three.
B. **NADH**: While NADH is indeed produced during the Krebs cycle, the focus of this question is on ATP generation, not NADH.
D. **0 ATP**: This option is incorrect because the Krebs cycle generates ATP molecules, specifically two per turn.
**Why the Correct Answer is Right:**
The Krebs cycle generates two ATP molecules per turn due to the oxidation of acetyl-CoA, which combines with oxygen and undergoes decarboxylation, and the reduction of NAD+ to NADH. This process provides energy, which is stored in ATP molecules. The cycle continues with other reactions involving succinyl-CoA, succinate, fumarate, malate, and oxaloacetate, ultimately leading to the production of two ATP molecules.
**Clinical Pearl:** Understanding cellular respiration and energy production is crucial for understanding the pathophysiology of diseases involving mitochondrial dysfunction, such as Leigh syndrome and Kearns-Sayre syndrome, which are characterized by impaired ATP production and can lead to severe neurological deficits.