Amino Acid Titration Curve

The document presents a titration curve for glycine, illustrating how the ionic state of an amino acid changes with pH.

Key points of the titration curve:

1. At low pH, glycine exists predominantly as a cation (positively charged ion).
2. As pH increases, there's a point where cations and zwitterions are present in equal amounts, exhibiting strong buffering capacity.
3. At the isoelectric point (pI), glycine exists entirely as zwitterions.
4. Further increase in pH leads to a mixture of zwitterions and anions, again with strong buffering capacity.
5. At high pH, glycine exists predominantly as an anion (negatively charged ion).

Definition: Buffering capacity refers to the ability of a solution to resist changes in pH when acids or bases are added.

This titration curve is essential for understanding how amino acids behave in different pH environments, which is crucial for various biochemical processes and laboratory techniques.

Highlight: The isoelectric point (pI) for glycine is shown to be around pH 6, which is characteristic for this amino acid.

Understanding titration curves is vital for predicting amino acid behavior in different physiological conditions and for designing experiments involving proteins.

Peptide Bond Formation

The final section explains the formation of peptide bonds, which is the fundamental process in protein synthesis.

Key points about peptide bond formation:

• Two amino acids react through a condensation reaction, releasing a water molecule.
• The peptide bond forms between the carboxyl group of one amino acid and the amino group of another.
• The resulting molecule is called a dipeptide.

Vocabulary: Condensation reaction - A reaction in which two molecules combine to form a larger molecule, typically with the loss of a small molecule such as water.

The document describes the structure of a peptide, including:

• N-terminal end
• C-terminal end
• Peptide bond

Highlight: The peptide bond is very stable, while the terminal ends can react further to form longer chains.

Classification of peptide chains:

• Oligopeptides: 2 to 9 amino acid residues
• Polypeptides: 10 to 100 amino acid residues
• Proteins: more than 100 amino acid residues

This information is crucial for understanding how individual amino acids come together to form the complex structures of proteins, which are essential for numerous biological functions.

Example: The dipeptide formed by alanine and glycine is shown, illustrating the peptide bond formation process.

The document also mentions mesomeric boundary formulas, which help explain the planar nature and partial double bond character of the peptide bond. This structural feature is critical for understanding higher-order protein structures.