Alpha Amino Acids Overview
Key Concepts
- Alpha Amino Acids: Essential for human physiology, differ from other amino acids like beta amino acids.
- Structure: Consists of a carbon (alpha carbon) with a carboxylic acid and an amine group attached.
- Alpha Carbon: Connects the carboxylic acid and the amine group in alpha amino acids.
Types of Amino Acids
- D and L Amino Acids:
- L Amino Acids: Used by humans, amine group on the left in Fischer projection.
- D Amino Acids: Not utilized by humans, used in bacterial strains.
Basic Structure
- R Group: Provides identity to amino acids. The variation in R groups leads to different amino acids.
- 20 Amino Acids in human body, categorized by the nature of their side chains.
Categories of Amino Acids
- Non-Polar Side Chains: Hydrophobic, includes glycine, alanine, valine, among others.
- Polar Side Chains:
- Charged Polar: Highly reactive, can pick up or lose protons, includes lysine, arginine.
- Uncharged Polar: Alcohol groups, amides, etc., remain neutral under physiological pH conditions.
pH and pKa
- pKa Values: Determine the ionization state of amino acids at different pH levels.
- Carboxylic Acids: Donate protons and become negatively charged at higher pH.
- Amines: Accept protons and become positively charged at lower pH.
Isoelectric Point (pI)
- pI Calculation: Average pKa values of carboxylic acid and amine for amino acids without ionizable side chains.
- Isoelectric Focusing: Used for amino acid separation based on pI.
Complex Amino Acids
- Arginine Example: Demonstrates the use of pKa values for determining ionic states at different pH levels.
- Di-Peptide Example: Illustrated how pI is calculated for more complex molecules.
Study Recommendations
- Review differences between D and L configurations.
- Understand how R groups influence amino acid properties.
- Familiarize with ionization states at different pH and how to use pKa for predictions.
Note: This is a study aid; always cross-reference with course materials and textbooks for comprehensive understanding.