Integrated SequencePhysics Chemistry Organic Biology

Web Resources

The Medical Biochemistry Page - Chemical Nature of the Amino Acids
Excellent survey of the following topics: Amino Acid Classification, Acid-Base Properties, Functional Significance of R-Groups, Optical Properties, and The Peptide Bond

Kimball's Biology Pages - Amino Acids

Virtual Textbook of Organic Chemistry - Proteins, Peptides & Amino Acids
Important facts about amino acid chemistry very well presented. Highly recommended.

Purdue University - Amino Acids
Excellent comprehensive discussion of the amino acids. Perfectly calibrated for the MCAT. (No, you probably don't have to have all the structures memorized, but it is good to recognize the characteristics of an amino acid from a given structure.) Includes a great discussion on amino acid titration.



  click if a link is broken



Special points of emphasis

Functional Groups in Organic Chemistry

Stereochemistry

Acids and Bases

Organic Acids and Bases

Reactions of Carboxylic Acids and Derivatives

Reactions of Amines

Proteins

You absolutely must be completely fluent on the basic structure of amino acids before you go into the MCAT. You do not necessarilly have to be able to identify them all, but you must be able to recognize the basic structure. α amino acids have a carboxyl group, amine group, hydrogen and a side chain bound to a central carbon (in proline, the amine group and the side chain have also formed a ring).

Except for glycine which is achiral, the α carbon is a chiral center whose configuration is normally specified using the D,L notational system. Amino acids from proteins in nature have the L configuration at their α carbon. (D and L symbols are associated with absolute configuration based on the dextrotatory and levorotatory forms of glyceraldehyde.)

α amino acids can be categorized based on whether their side chain is nonpolar, polar (but nonionizable), acidic or basic. Because there is both an amine group and a carboxyl group bound to the central carbon, amino acids are amphoteric. The isoelectric point is the pH at which an amino acid bears no net charge, corresponding to the pH of maximum zwitterion concentration. For amino acids without additional ionizable groups on their side chains, the isoelectric point occurs in a solution that is close to neutral pH (the pKa of the amine is greater than 7 while the pK+ of the carboxyl group is less than 7). For those with ionizable side chains, the isoelectric point is far from neutrality.




Functional Groups in Organic Chemistry

Organic Acids and Bases

Reactions of Carboxylic Acids and Derivatives

Reactions of Amines

Proteins

Gene Expression

In peptide bond formation, the amine group of one amino acid undergoes dehydration with the carboxyl group of another in an acyl exchange mechanism, forming an amide linkage. This process occurs in live cells on ribosomes as they translate the sequence of nucleotides in mRNA into the amino acid sequence of proteins.







The WikiPremed MCAT Course is a free comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum.

Please read our policies on privacy and shipping & returns.  Contact Us.
MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course.


Creative Commons License
The work of WikiPremed is published under a Creative Commons Attribution Share Alike 3.0 License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions. You can use the resources here for commercial or non-commercial purposes, but please give attribution and a link to the production credits and edit history of the resource. For the works here which began as my individual work, please attribute "John Wetzel, an author at wikipremed.com".