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The Urea Cycle
Important Points About the Urea Cycle:

Why does the Urea Cycle exist? When Amino Acids are broken down (for example, when you eat proteins), the nitrogen leftover is largely converted to urea with the Urea Cycle. It then leaves the body in the form of urine. .

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Urea Cycle Location: Ammonia travels to the liver's mitochondria where it's converted to carbamoyl phosphate. Carbamoyl phosphate is converted into citrulline in the mitochondria before going to the cytosol when arginosuccinate converts it into arginosuccinate in the cytosol. 
 

Mnemonics:

Intermediate Mnemonic 

Ammonia can create a lot (of) fumarate and urea, ok?

Ammonia - Ammonia 

Can - Carbamoyl Phosphate - Isocitrate

Create = Citrulline - alpha-ketoglutarate

A lot (of) - Arginosuccinate - Succinyl-CoA

Fumarate - Fumarate (can enter TCA/Krebs)

And - Arginine

Urea - Urea

Ok? - Ornithine 

Review Videos:

  • The Urea Cycle by Andrey K- AK is good if you prefer simplified, but quickly presented information. Our personal experience is that these lectures are great for students who are already on the path to burnout because he doesn't take too much of your time. He also hits on the biochemical details that are important so you have a frame of reference for what's happening with the molecules as they go through the cycle. 

  • The Urea Cycle by NinjaNerd  - NinjaNerd is the best channel for really understanding biochemical pathways and where they go wrong instead of just memorizing words. 

  • Uric Acid Recycling - This Osmosis video is not just about the Urea Cycle, but about how the kidney handles uric acid. An understanding of what is happening within the body on a slightly more macro level is important so you know how and where the biochemistry matters.
     

Other Resources: 

  • The Urea Cycle Step by Step - For those who prefer to read information instead of watch lectures, this is a very easy to understand breakdown of the Urea Cycle including well designed drawings.  

  • Urea Cycle Overview - Pharmacy180 has a lot of ads, but if you don't mind, they also have a ton of useful study pages and overviews. This page includes highlights of the urea cycle, important reactions, regulation information, and very clear images that include chemical structures. 

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