Question

Glycine has the zwitterion structure shown. Draw the structure and give the net charge of glycine that will predominate at the indicated pH values (pI = 6.0).b. pH 12.0

Accepted Answer

Understand the concept of a zwitterion: A zwitterion is a molecule that has both positive and negative charges but is overall electrically neutral. Glycine, an amino acid, exists as a zwitterion at its isoelectric point (pI), which is pH 6.0 in this case. At pH values above the pI (e.g., pH 12.0), the environment is basic, meaning there is a low concentration of H⁺ ions. This will affect the protonation state of glycine's functional groups. Identify the functional groups in glycine: Glycine has an amino group (-NH₃⁺ in its protonated form) and a carboxylic acid group (-COO⁻ in its deprotonated form). At pH 12.0, the amino group will lose a proton, becoming -NH₂, while the carboxylic acid group remains deprotonated as -COO⁻. Determine the net charge: At pH 12.0, the amino group (-NH₂) is neutral, and the carboxylate group (-COO⁻) carries a negative charge. Therefore, the net charge of glycine at pH 12.0 is -1. Draw the structure: The structure of glycine at pH 12.0 will have the central carbon atom bonded to a hydrogen atom, a -CH₂ group, a neutral -NH₂ group, and a negatively charged -COO⁻ group. This reflects the deprotonated state of glycine in a basic environment.

Glycine has the zwitterion structure shown. Draw the structure and give the net charge of glycine that will predominate at the indicated pH values (pI = 6.0).
b. pH 12.0

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Zwitterion Structure

Isoelectric Point (pI)

pH and Charge Relationship