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(BSN) Bachelor Biochemistry Protein Cheat Sheet

John Marsh
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  • Full Document

Biochemistry Protein Cheat Sheet

  • UniversityTrinity University of Asia
  • CourseBachelor of Science in Nursing (BSN)

The proteins in all living species, from bacteria to humans, are constructed from the same set of 20 amino
acids, so called because each contains an amino group attached to a carboxylic acid. The amino acids in
proteins are α-amino acids, which means the amino group is attached to the α-carbon of the carboxylic
acid. Humans can synthesize only about half of the needed amino acids; the remainder must be obtained
from the diet and are known as essential amino acids. However, two additional amino acids have been
found in limited quantities in proteins: Selenocysteine was discovered in 1986, while pyrrolysine was
discovered in 2002.
The amino acids are colorless, nonvolatile, crystalline solids, melting and decomposing at temperatures
above 200°C. These melting temperatures are more like those of inorganic salts than those of amines or
organic acids and indicate that the structures of the amino acids in the solid state and in neutral solution
are best represented as having both a negatively charged group and a positively charged group. Such a
species is known as a zwitterion.
In addition to the amino and carboxyl groups, amino acids have a side chain or R group attached to the αcarbon. Each amino acid has unique characteristics arising from the size, shape, solubility, and ionization
properties of its R group. As a result, the side chains of amino acids exert a profound effect on the
structure and biological activity of proteins. Although amino acids can be classified in various ways, one
common approach is to classify them according to whether the functional group on the side chain at
neutral pH is nonpolar, polar but uncharged, negatively charged, or positively charged. The structures and
names of the 20 amino acids, their one- and three-letter abbreviations, and some of their distinctive
features are given in Table




 (BSN) Bachelor Biochemistry Protein Cheat Sheet

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