A Level Biology Practice Exam 2025 – All-in-One Study Guide to Excel in Your A Levels!

Y-shaped glycoproteins that function as antibodies are known as immunoglobulins. These proteins play a crucial role in the immune system by identifying and neutralizing foreign objects such as bacteria and viruses. Each immunoglobulin has specific regions that bind to particular antigens, which are the foreign molecules that elicit an immune response.

The Y-shaped structure of immunoglobulins allows them to have two identical binding sites, facilitating the cross-linking of antigens and enhancing their elimination from the body. This structure is key to their function in identifying and responding to pathogens.

Other terms in the options, such as amino acids, antigens, and ligands, refer to different biological molecules. Amino acids are the building blocks of proteins, antigens are substances that induce an immune response, and ligands refer to molecules that bind specifically to other molecules, typically proteins, but do not have the specific immunological functions attributed to immunoglobulins.