Which protein structure is typical of antibodies and some enzymes that act in cell synthesis?

Which protein structure is typical of antibodies and some enzymes that act in cell synthesis?

• A. Primary structure
• B. Quaternary structure
• C. Secondary structure
• D. Tertiary structure

Answer: (B)

Quaternary structure is about how multiple polypeptide chains come together to form a functional protein complex. Antibodies are built from two heavy chains and two light chains linked by disulfide bonds, so their功能 depends on the arrangement of several chains into a single, active architecture. Many enzymes that act in cell synthesis likewise operate as multi-subunit assemblies; the coordinated interaction of distinct subunits creates the complete active site and allows regulation that a single chain couldn’t provide. In contrast, primary structure is just the amino acid sequence, secondary structure refers to local folding like helices and sheets within a single chain, and tertiary structure is the overall three-dimensional shape of one polypeptide. Since antibodies and these multi-subunit enzymes rely on multiple chains coming together, the relevant level is quaternary structure.

Quaternary structure is about how multiple polypeptide chains come together to form a functional protein complex. Antibodies are built from two heavy chains and two light chains linked by disulfide bonds, so their功能 depends on the arrangement of several chains into a single, active architecture. Many enzymes that act in cell synthesis likewise operate as multi-subunit assemblies; the coordinated interaction of distinct subunits creates the complete active site and allows regulation that a single chain couldn’t provide.

In contrast, primary structure is just the amino acid sequence, secondary structure refers to local folding like helices and sheets within a single chain, and tertiary structure is the overall three-dimensional shape of one polypeptide. Since antibodies and these multi-subunit enzymes rely on multiple chains coming together, the relevant level is quaternary structure.