Introduces α-amino acids, their carboxyl and amino groups on adjacent carbons, and their classification into neutral, acidic and basic types by side chain. Covers chirality and the L-configuration, the eight essential amino acids with a mnemonic, acid-base behaviour with a glycine titration curve and isoelectric point, zwitterions, and typical chemical reactions. Closes with ninhydrin and amino acid analysis for diagnosis.
Topic 31 of 42 in the MU Sofia syllabus for Chemistry (Dental Medicine, Year 1). The free AceMed note covers it in 8 sections, about 920 words (6 min of reading), with 19 flashcards.
In this note
α-Amino acids - structure, nomenclature,
Stereochemistry.:
Essential amino acids.
Acid-base properties
Isoelectric point.
Chemical properties.
Esterification, acylation and interaction with formaldehyde and ninhydrin.
Amino acid analysis - diagnostic significance.
α-Amino acids - structure, nomenclature,
Amino acids:
Contain carboxylic acid group (-COOH) and amino group (-NH2).
Usually α- to the carboxylic acid (means they are attached to adjacent carbon atoms in the molecule) .
Classified as α-, β-, γ-, etc. based on relative positions of functional groups.
α-Amino acids:
Most important biologically.
Amino and carboxyl groups are α- to each other.
Structures may have various functional groups.
Classification based on functional groups:
I. Neutral:
I.1. Non-polar R-groups.
I.2. Non-charged polar (non-ionized) R-groups.
II. Acidic:
Contain acidic functional groups.
III. Basic:
Contain basic functional groups.
Stereochemistry.:
Amino acids are chiral molecules.
Except for glycine, which has two identical substituents on the α-carbon, α-amino acids have four different substituents, making them chiral.
The α-carbon is the chiral center.
Naturally occurring amino acids predominantly exist in the L-configuration, where the amino group is on the left side when the carboxyl group is at the top.
The D-configuration also exists but is less common in naturally occurring proteins.
The stereochemistry of amino acids is crucial for the folding and function of proteins.
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