End product of citric acid/Kreb's cycle is

Options

A. citric acid
B. lactic acid
C. Pyruvic acid
D. `CO_(2) + H_(2)O`

Explanation

To determine the end product of the citric acid or Krebs cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a series of biochemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate derived from carbohydrates, fats, and proteins.

2. **Formation of Citric Acid**: The cycle begins with the combination of acetyl-CoA and oxaloacetate to form citric acid (citrate). This is the first stable product of the cycle.

3. **Products of the Cycle**: As the cycle progresses, citric acid undergoes a series of transformations. During these transformations, several key products are generated:
- **NADH**: Four molecules of NADH are produced (three from the cycle and one during the conversion of pyruvate to acetyl-CoA).
- **FADH2**: One molecule of FADH2 is produced.
- **ATP (or GTP)**: One molecule of ATP (or GTP) is produced directly in the cycle.
- **Carbon Dioxide**: For every two molecules of pyruvate that enter the cycle (derived from one molecule of glucose), six molecules of carbon dioxide are released.

4. **End Products**: The end products of the Krebs cycle are:
- **Carbon Dioxide (CO2)**: Released as a waste product.
- **Water (H2O)**: Formed during the electron transport chain as a final product of respiration.
- **Energy in the form of NADH and FADH2**: These are used in the electron transport chain to produce ATP.

5. **Conclusion**: Therefore, the end products of the Krebs cycle are primarily carbon dioxide and water, along with energy carriers (NADH and FADH2) that will be used in further stages of cellular respiration.

### Final Answer:
The end products of the citric acid/Krebs cycle are carbon dioxide and water.

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