By which process and where, the urea is synthesized?

Explanation

### Step-by-Step Solution:

1. **Understanding Urea**: Urea is a nitrogenous waste product that is primarily found in humans and mammals. It is a result of protein metabolism and is excreted from the body.

2. **Location of Synthesis**: Urea is synthesized in the liver, specifically in the hepatocytes, which are the main functional cells of the liver. Hepatocytes make up about 80% of the liver's mass.

3. **Process of Synthesis**: The synthesis of urea occurs through a biochemical process known as the **urea cycle** or **ornithine cycle**. This cycle converts ammonia, which is toxic, into urea, which is less harmful and can be excreted.

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