Properties of Amino Acids

All amino acids have (structure wise — 4 parts)

1. carboxyl group (pka ~ 10) negatively charged when neutral

2. amino group (pka ~ 2) positively charged when neutral

3. single carbon atom (alpa-carbon)

4. unique side chain, called R group

What links Amino acids

peptide bonds via hydration reactions between amino acids

List non-polar Amino Acids

Amino acids with hydrophobic side chains such as alanine(A), valine(V), leucine(L), isoleucine(I), methionine(M), phenylalanine(F), and tryptophan(W)

• Great for hydrophobic interactions and van der waals forces

• C-H

List polar uncharged Amino Acids

Amino acids with polar side chains that do not carry a charge, such as serine (S), threonine (T), tyrosine (Y), asparagine (N), and glutamine (Q).

• These amino acids are involved in hydrogen bonding and can interact with water.

• hydrophilic

• partial + and - charge

• S,T, Y → phosphorylated

List polar charged Amino Acids

Amino acids with side chains that carry a positive or negative charge, such as aspartate (D), glutamate (E), lysine (K), arginine (R), and histidine (H).

• These amino acids are highly hydrophilic and participate in ionic interactions

• fully + and - charges

Acidic Amino Acids

Amino acids with negatively charged side chains at physiological pH, primarily aspartate (D) and glutamate (E). These play crucial roles in enzyme activity and neurotransmission.

Basic Amino Acids

Amino acids with positively charged side chains at physiological pH, primarily lysine (K) and arginine (R). These amino acids are essential for protein structure and function, often involved in binding negatively charged molecules.

List unique Amino Acids

3 types:

• Glycine, flexible and can tightly pack with its one hydrogen atom — small

• Proline, with a unique cyclic structure, introduces kinks in protein chains — breaks secondary structure

• Cysteine, containing a thiol group (SH), forms disulfide bonds for stabilization

Alanine

• Ala

• non-polar amino acid with a simple methyl side chain

Valine

• Val

• non-polar amino acid with a branched isopropyl side chain

Leucine

• Leu

• non-polar amino acid with a branched isobutyl side chain

Isoleucine

• Ile

• non-polar amino acid with a branched side chain containing both aliphatic and hydrophobic properties

Methionine

• Met

• Sulfur-containing non-polar amino acid with a thioether side chain

Phenylalanine

• Phe

• Aromatic non-polar amino acid with a benzyl side chain

Tryptophan

• Trp

• Aromatic non-polar amino acid with an indole side chain

Serine

• Ser

• Polar uncharged amino acid with a hydroxymethyl side chain

Threonine

• Thr

• Polar uncharged amino acid with a hydroxyl side chain

Glutamine

• Gln

• Polar uncharged amino acid with an amide side chain

Asparagine

• Asn

• Polar uncharged amino acid with an amide side chain

Tyrosine

• Tyr

• Polar uncharged amino acid with a phenolic side chain

Aspartic Acid

• Asp

• Polar charged acidic amino acid with a carboxylic acid side chain

Glutamic Acid

• Glu

• Polar charged acidic amino acid with a carboxylic acid side chain

Lysine

• Lys

• Polar charged basic amino acid with an amino group in its side chain

Arginine

• Arg

• Polar charged basic amino acid with a guanidinium group in its side chain

Histidine

• His

• Polar charged basic amino acid with an imidazole side chain

Glycine

• Gly

• Non-polar, aliphatic (hydrophilic or hydrophobic) amino acid and the simplest amino acid with a hydrogen atom as its side chain.

Cysteine

• Cys

• Polar, uncharged amino acid known for its thiol side chain capable of forming disulfide bonds.

Proline

• Pro

• Non-polar, aliphatic amino acid with a unique cyclic structure that influences protein stability and folding.