20 Amino Acids: Structures and Functions

Study Notes

Amino Acids Overview

Glycine (Gly, G): Smallest amino acid, achiral; important for fitting into tight turns in peptide chains without affecting hydrogen bonding with water.
Alanine (Ala, A): Comprises three carbons with a simple methyl group; does not exhibit hydrophobic properties despite being non-polar.
Valine (Val, V): Branched and bulky, hydrophobic with a distinctive "V" shape due to two methyl groups close to the peptide backbone.
Leucine (Leu, L): Similar to valine but with one additional carbon; branched at the gamma-carbon, contributing to its hydrophobic nature.
Isoleucine (Ile, I): Shares the same carbon count as leucine but with a unique methyl group distribution at the beta and gamma positions.

Aromatic Amino Acids

Phenylalanine (Phe, F): Contains an aromatic ring, making it hydrophobic similar to alanine but with increased complexity in structure.
Tryptophan (Trp, W): Features two aromatic rings; less hydrophobic than phenylalanine and includes an indole group, impacting its function in proteins.
Tyrosine (Tyr, Y): Possesses both hydrophobic and hydrophilic properties based on location within proteins, also contains a hydroxyl (-OH) group influencing its interactions.

Polar Amino Acids and Their Characteristics

Histidine (His, H): Contains an imidazole ring with two nitrogen atoms, capable of acting as a base due to protonation under physiological conditions.
Lysine (Lys, K): Basic amino acid that gains a positive charge at physiological pH; functions similarly to histidine in terms of proton acceptance.
Arginine (Arg, R): Basic and positively charged at physiological pH due to a guanidinium group; classified with histidine and lysine as key basic amino acids.

Acidic Amino Acids

Aspartate (Asp, D): Acts as an acid, carrying a negative charge at physiological pH; functions as the conjugate base of aspartic acid, containing a four-carbon structure.
Glutamate (Glu, E): Similar to aspartate but possesses five carbons; acts as an acid and negatively charged under physiological conditions, serving as the conjugate base of glutamic acid.

Additional Amino Acids

Asparagine (Asn, N): Polar amino acid functioning as an amide derivative of aspartate; includes a reactive sulfhydryl group, contributing to disulfide bond formation.
Methionine (Met, M): Non-polar amino acid with a thioether linkage; serves as the first amino acid introduced during the protein translation process.
Proline (Pro, P): Distinguished by its imino acid structure, causing kinks in peptide backbones; facilitates structural changes due to its unique bonding involving the alpha-amino group.

Description

Test your knowledge of the 20 amino acids with this flashcard quiz. Each card presents essential information about their structures, functions, and unique properties. Perfect for students studying biochemistry or molecular biology.