A Level Biology Practice Exam

What is the significance of the association of protein subunits?

1. It determines the primary structure of proteins

2. It is essential for metabolic activity and regulation

3. It impacts the number of haploid cells produced

4. It supplies energy for the cell's operations

The correct answer is: It is essential for metabolic activity and regulation

The association of protein subunits is vital for metabolic activity and regulation because many proteins function as multi-subunit complexes. These complexes can exhibit cooperative interactions among their subunits, meaning the binding of one molecule can enhance or inhibit the binding of others, thus playing a crucial role in enzymatic activity and signaling pathways. This assembly often alters the protein's functional properties, allowing it to perform specific tasks such as catalyzing reactions, transducing signals, or regulating cellular processes. Additionally, the spatial arrangement and interactions of these subunits are critical in determining the protein's overall activity and stability. For instance, in enzymes, the active site may be formed by the spatial arrangement of subunits, allowing substrates to bind effectively and undergo a reaction. Moreover, some proteins may require alterations in their subunit structure or composition for their activity to be regulated by various cellular signals, further highlighting the importance of subunit interactions in metabolic activities. The other options do not accurately reflect the role of protein subunit association. The primary structure of proteins is defined by the sequence of amino acids and does not involve their subunit interactions, while haploid cell production relates more to genetics and cellular division, rather than protein structure. Lastly, although proteins can be involved in energy