3.5 Amino Acids
Amino acids are building blocks that join together to form proteins
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Figure 3.13 Basic structure of an amino acid.
Amino acid molecules have a central carbon-hydrogen molecule attached to three parts:
- the carboxylic acid group, containing carbon and oxygen
- the amino group, containing nitrogen and hydrogen
- the side chain (the R group), which varies by amino acid and contains one or more of the following: hydrogen, carbon, oxygen, nitrogen, sulfur, phosphorus, sulfur, and selenium. The 21 common amino acids with their various side chains are depicted below.
![](https://open.lib.umn.edu/app/uploads/sites/206/2018/10/21amino.png)
The amino acids pictured above combine to form proteins when the carboxyl group from one amino acid and the amino group from another chemically react and form a bond. RNA helps guide the amino acid assembly to create a chain of amino acids called a polypeptide or a protein. This chain of amino acids folds into a functional protein based on the properties of the amino acid side chains. The resulting proteins can have a variety of functions in an organism based on each protein’s shape. Watch this short video describing the function of various proteins:
![](https://open.lib.umn.edu/app/uploads/sites/206/2017/08/Check-Yourself-Icon-01-186x300.png)
Check Yourself
- By OrgoGuy2theRescue - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=55068925 ↵