Chapter 28: Problem 27

Describe what is meant by each of the following terms, using specific examples where appropriate: (a) \(\alpha\) -amino acid; (b) zwitterion; (c) isoelectric point; (d) peptide bond; (e) tertiary structure.

Short Answer

Expert verified

The \(\alpha\)-amino acid is a molecule with a –COOH and –NH2 group attached to the same carbon. A zwitterion is a neutral molecule with balanced positive and negative charges. The isoelectric point is the pH at which a molecule has no net charge. A peptide bond forms between two amino acids when one's carboxyl group reacts with another's amino group, releasing water. Lastly, the tertiary structure of a protein refers to the 3D arrangement of its polypeptide chain stabilized by R group interactions.

Step by step solution

Define \(\alpha\)-amino acid

An \(\alpha\)-amino acid is a molecule that contains both a carboxyl (–COOH) and an amino (–NH2) functional group. Specifically, they are attached to the same carbon in the molecule, which is the \(\alpha\)-carbon. An example is glycine, the simplest \(\alpha\)-amino acid.

Define Zwitterion

A zwitterion is a molecule that carries a positive and negative charge, but is overall neutral because the charges balance each other out. In the case of \(\alpha\)-amino acids, the carboxyl group can lose a proton (H+) and the amino group can gain a proton, resulting in a zwitterion.

Define Isoelectric Point

The isoelectric point (pI) is the specific pH at which a molecule carries no net electric charge. For \(\alpha\)-amino acids, it's the pH at which the amino acid forms a zwitterion.

Define Peptide Bond

A peptide bond is a chemical bond formed between two amino acids when the carboxyl group of one molecule reacts with the amino group of the other, releasing a molecule of water (H2O). This is a dehydration synthesis reaction.

Define Tertiary Structure

The tertiary structure of a protein is the three-dimensional (3D) shape formed when its polypeptide chain folds and bends in space. This structure is predominantly stabilized by interactions between the R groups of the amino acids, including hydrogen bonding, ionic interactions, and hydrophobic packing.

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Describe what is meant by each of the following terms, using specific examples where appropriate: (a) \(\alpha\) -amino acid; (b) zwitterion; (c) isoelectric point; (d) peptide bond; (e) tertiary structure.

Short Answer

Step by step solution

Define \(\alpha\)-amino acid

Define Zwitterion

Define Isoelectric Point

Define Peptide Bond

Define Tertiary Structure

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