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Question Video: Identifying the Source of Urea Biology

What substance (or substances) is urea formed by the breakdown of?


Video Transcript

What substance, or substances, is urea formed by the breakdown of?

This question is asking us about urea, which is a waste product excreted in the urine. Before answering our question, let’s first describe what the excretory system is.

Metabolism is the sum of all chemical reactions in the body. These reactions are important for almost every process ranging from the breakdown of food molecules for energy to the synthesis of biological macromolecules. These chemical reactions can produce products that aren’t always useful for the human body, or are sometimes toxic. These are known as waste products. Here are some examples of waste products produced by the body. Carbon dioxide, as you might recall, is produced as a by-product of cellular respiration, which produces energy from the breakdown of glucose.

The process of removing waste from the body is called excretion, and many organs are involved in this process. Some of these organs include the lungs, liver, and kidneys. These organs make up the excretory system, although they also belong to other organ systems as well.

Urea is excreted by the kidneys and is the result of the breakdown of amino acids from proteins. You’ll recall that amino acids are the monomer subunits of proteins. When amino acids are broken down, the amino group is converted into a toxic substance called ammonia. The liver is responsible for converting toxic substances, like ammonia, into less toxic ones. Ammonia is actually converted into urea by the liver.

Urea is a major component of the urine, which is formed by the filtering actions of the kidneys. The kidneys are able to filter the blood’s contents, carrying waste and excess ions away to make urine, while only allowing useful compounds to be reabsorbed into the body.

Getting back to our question, amino acids are the substances that are broken down to form urea.

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