Ace A Level Biology 2026 – Dive Deep and Conquer Science!

Antibodies are indeed best described as Y-shaped glycoproteins produced by B cells in response to toxins and pathogens. They play a critical role in the immune response by specifically binding to antigens, which are the foreign substances such as toxins or pathogens that trigger an immune response. This binding can neutralize the toxins directly, or mark pathogens for destruction by other immune cells. The structural Y-shape allows antibodies to effectively interact with their target antigens, providing a mechanism for the immune system to remember and quickly respond to previously encountered threats.

The other choices describe different aspects of immune function but do not accurately characterize antibodies. For example, antibodies do not directly kill bacteria; rather, they facilitate the immune response that may lead to the destruction of bacteria by signaling other components of the immune system. Similarly, antibodies are not enzymes; they do not promote bacterial growth or function as cells; they are proteins produced by B cells that engage in adaptive immunity. Understanding this distinction is key to grasping the broader concepts of immunology and the specific roles that different components of the immune system play.