Let's start with cysteine.
- Cysteine is our second amino acid that contains a sulfur atom (the first was methionine).
- We also write cysteine as Cys or C.
- Draw our general amino acid structure, and add a methyl group.
Do you remember what amino acid has this structure? It's alanine!
- Now add a sulfhydryl (SH) group to alanine.
- The sulfhydryl group of cysteine is very important because it forms disulfide bridges, an important part of protein structure.
Amino Acid: Polar
Polar
The polar amino acids are: cysteine, serine, threonine, asparagine and glutamine.
Cysteine
- Contains a sulfur atom.
- The sulfhydryl group forms disulfide bridges, an important part of the protein structure.
Serine
- Serine is cysteine's cousin because they are identical except for one atom: it has an oxygen atom in place of the sulfur atom.
- Serine is one of the most commonly phosphorylated amino acids, which makes it very important in the activation and deactivation of proteins.
Threonine
- Threonine has a branch at the beta carbon.
Asparagine
Glutamine
- The carboxamide correlate of glutamate.