What is meant with the “zwitterionic form” of an amino acid?b. Incorporation proline in a peptide chain induces new properties/restrictions typical for this amino acid.Describe two of these properties/ restrictions.c. The 3D structure of many proteins is lost when exposed to 0.1 M beta mercaptoethanol (CH2OH-CH2SH).

a. The "zwitterionic form" of an amino acid refers to the state in which the amino acid has both a positive and negative charge, but is overall neutral. This occurs when the carboxyl group (-COOH) loses a proton (H+) and the amino group (-NH2) gains a proton. This form is prevalent in physiological pH conditions.

b. Proline is unique among the 20 standard amino acids because its side chain forms a cyclic structure that includes the backbone nitrogen. This structure imposes two main restrictions/properties:

1. Rigidity: The cyclic structure of proline restricts the flexibility of the polypeptide chain, often inducing a bend in the chain or limiting the types of secondary structure that can form.

2. Disruption of secondary structures: Proline is often found at the start of alpha helices or in the turns of beta sheets because it can disrupt regular secondary structures due to its unique geometry.

c. Beta-mercaptoethanol (CH2OH-CH2SH) is a reducing agent that can break disulfide bonds (S-S bonds) in proteins. These bonds are crucial for maintaining the 3D structure of many proteins. When exposed to 0.1 M beta-mercaptoethanol, these disulfide bonds are broken, causing the protein to lose its 3D structure and denature. This process is often reversible if the reducing agent is removed and the correct conditions for forming disulfide bonds are restored.