Question

1. explain the difference between an allosteric activator and an allosteric inhibitor.
2. although it is not an enzyme, hemoglobin shows cooperativity in binding o₂. use o₂ binding in fish hemoglobin to explain cooperativity.
3. study this figure from your book (figure 8.21) and answer the questions that follow.

Explanation:

1. An allosteric activator binds to a site other than the active - site of a protein (usually an enzyme), causing a conformational change that increases the protein's activity. An allosteric inhibitor also binds to a non - active site but causes a conformational change that decreases the protein's activity.
2. In fish hemoglobin, when one molecule of O₂ binds to one of the subunits of the hemoglobin tetramer, it causes a conformational change in that subunit. This change makes it easier for other O₂ molecules to bind to the remaining subunits. This is cooperative binding, where the binding of one ligand (O₂) affects the binding of subsequent ligands to the same protein.

Answer:

1. An allosteric activator increases protein activity by inducing a favorable conformational change upon binding to a non - active site, while an allosteric inhibitor decreases protein activity through a conformational change upon non - active site binding.
2. Binding of one O₂ to a subunit of fish hemoglobin induces a conformational change that enhances the binding of additional O₂ to other subunits, demonstrating cooperativity.