Finally, the green circle represents the amino group. The purple circle represents the carboxyl group. The blue circle indicates the central carbon. In the image, the red circle represents the R group – in this case, CH. Please note that we are not counting Selenocysteine (Sec, U), and you will not be expected to know it on the MCAT:
The twenty amino acids you will need to know are listed below. This makes it convenient to write out long chains of amino acids – the protein Titin, for example, is a sequence of 27,000 amino acids. Each of these will have a name, a 3-letter abbreviation, and a 1 letter abbreviation. While there are hundreds of different amino acids that exist, there are only 20 that are used by the human body for protein synthesis. What do I need to know about Amino Acid Classification for the MCAT?
#CALCULATE PI OF PEPTIDE CHAIN HOW TO#
Take the time to learn how to do this and make sure you understand it. An L-amino acid will not always be S, and a D-amino acid is not always R. Similarly, if the priority of the amino acid is NH2 > R > COOH, then an L-amino acid is the same as an S-amino acid and a D-amino acid is the same as a S-amino acid.Ī Common Misconception: L and D configurations of amino acids are different from R and S configurations of organic molecules. If the priority of the amino acid is NH2 > COOH > R, then an L-amino acid is the same as an S-amino acid and a D-amino acid is the same as a R-amino acid. To determine the configuration of an Amino Acid, you must compare the priority of the side groups of Amino Acids (A step-by-step instruction on how to do this will be covered in organic chemistry and determine the R- and S-configuration of carbon molecules). D-Amino Acids occur much less often in nature and, as a result, aren’t commonly used as a component in proteins. L-Amino Acids are more commonly found in nature, and in the human body, and are typically the type that are found in proteins. These configurations are commonly classified as L- or D-conformation. Although an amino acid may have the same functional components as another, the orientation of the side groups around the α carbon may change the overall properties of the molecule.
When learning about Amino Acids for the MCAT, you also need to understand Amino Acid configurations to ensure you are maximising your potential of getting a good MCAT score. Different side chains will give the Amino Acid a different property, allowing it to interact with its environment in different ways. Arguably the most important component of the amino acid is the side chain. These groups are rotated around the α carbon in particular ways that allow them to interact with other amino acids. As you can see, there are 4 important components bound to a central carbon, called the α (alpha) carbon.
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