University:
York University
Course:
BIOL 2020 | Biochemistry
Academic year:

2023
Views:

300

Pages:

2
Author:

Nick T.

Amino Acids Special groups Cystine (-S-S-) Side chain contains two -SH groups Can combine by (oxidation) to form a disulfide two cysteines can combine to form a disulfide Proline (Pro) the alpha Carbon back to the amino group in a ring Proline puts a kink or twist in the structure any protein that contains it Glycine (Gly) Side chain is only H So Small it allows sharp bends & twists in protein chains Will NOT form attractions to other amino acids in a protein Intermolecular Forces interactions between the amino acids in a protein determine its Structure Nonpolar amino acids have hydrocarbon Side Chains Only London Dispersion forces Polar neutral amino acids have polar amide groups Hydrogen bonding Polar acidic amino acids have negative charge attract to polar basic amino acids Full has positive charge Charge-Charge interactions Amino Acids In presence of water Nonpolar amino acids * hydrophobic water fearing No H-bonding No dipole dipole Polar amino acids (basic and acidic) * hydrophilic water loving H-bonding Dipole Dipole Charged Amino Acid are both acids + base Carboxylic acid group pKa between 2-3 Amine group pKa between 9-10 At physiological pH (7.4) Carboxylic acid group loses proton has - charge Amino group accepts proton has + charge Zwitterion a neutral, dipolar ion has one + charge and one - charge at physiological pH, amino acids are Zwitterions Change increases water solubility even the free non polar amino acids are soluble b/c have NH3+ COO- Amino acid proteins are generally L-amino acids