In which of the following phosphorylation in absent:

Options

A. Glycolysis
B. kreb cycle
C. `C_(4)` cycle
D. ETS

Answer

To solve the question "In which of the following phosphorylation is absent?", we will analyze each option provided:

**Step 1: Understand the concept of phosphorylation**
Phosphorylation is a biochemical process that involves the addition of a phosphate group to a molecule, which can affect the function and activity of that molecule. It is a key process in various metabolic pathways.

**Step 2: Analyze each option**
- **A. Glycolysis**: This is a metabolic pathway that converts glucose into pyruvate, producing ATP and NADH in the process. Phosphorylation occurs in glycolysis, specifically in the conversion of glucose to glucose-6-phosphate and in other steps.

- **B. Krebs Cycle (Citric Acid Cycle)**: This cycle is a series of chemical reactions used by all aerobic organisms to generate energy. Phosphorylation occurs here as well, particularly in the formation of ATP from ADP and inorganic phosphate.

- **C. C4 Cycle (Hatch-Slack Pathway)**: This is a photosynthetic pathway used by certain plants to fix carbon dioxide. In the C4 cycle, there is no direct phosphorylation involved in the initial steps of carbon fixation, as it uses a different mechanism to concentrate CO2 for the enzyme Rubisco.

- **D. Electron Transport System (ETS)**: This is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions. Phosphorylation occurs here in the form of oxidative phosphorylation, where ATP is produced.

**Step 3: Conclusion**
Based on the analysis, the only option where phosphorylation is absent is the **C. C4 Cycle**.

**Final Answer: C. C4 Cycle**

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