Amino acids 2: Degradation and synthesis

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Headshot of Ted Chauvin, PhD · Associate Professor
Ted Chauvin
PhD · Associate Professor
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There is one chapter for suggested reading from Lippincott, Chapter 20: Amino Acids: Degradation and Synthesis. The short descriptions listed below are some of the big-picture, high-yield points. The reading and the class session will go into more depth and detail. The reading guides are also posted.

As I have said in other modules, this reading guide is for people who need help focusing on these chapters. Most students DO NOT need to use the guide.

Amino Acids: Degradation and Synthesis. Lippincott® Illustrated Reviews: Biochemistry, 8e. Medical Education: Health Library.pdf.

Describe the role of folic acid in amino acid metabolism

Chapter 20, Lippincott Illustrated Reviews: Biochemistry, 7e.

Folic acid is the synthetic form of folate, a water-soluble B vitamin that takes part in several critical functions in the human body. The active form of folate is tetrahydrofolic acid. It serves in one carbon reductions reactions. These reactions are involved in the synthesis of nucleotides and amino acids. The amino acids requiring folic acid for metabolism are methionine, cysteine, serine, glycine, and histidine. Folic acid also serves as a coenzyme in converting methionine to homocysteine.

Diagram and describe how the different classes of amino acids are metabolized and what occurs (at the biochemical level) when there are defects in amino acid metabolism

The big take-home here is that you need to know and understand phenylketonuria, maple syrup urine disease, and homocystinuria. See also this alkaptonuria video.

Chapter 20, Lippincott Illustrated Reviews: Biochemistry, 7e.

Define nonessential amino acids and describe their synthesis

Note

Non-essential amino acids can be made by the body. Essential amino acids must come from the diet.

Synthesis from α-keto acids
Alanine, aspartate, and glutamate
Transamination reactions
Synthesis by amidation
Glutamine and Asparagine
Related to on-carbon donors and one-carbon acceptors (think folic acid)
Serine, glycine, and cysteine
This relates to the first learning goal in this session.
From phenylalanine
Tyrosine
In patients with PKU, tyrosine becomes essential.
From glutamate
Proline and arginine
Note: Arginine can also be made via the urea cycle
It would be good to know the essential versus nonessential amino acids. It would be a bonus if you can remember which ones are glucogenic, ketogenic, or both (although not as high-yield). Chapter 20, Lippincott Illustrated Reviews: Biochemistry, 7e.