Please answer the following question: Answer the following question given this paragraph: Proteins play many important roles in living things. Some proteins help cells keep their shape, and some make up muscle tissues. Many proteins speed up chemical reactions in cells. Other proteins are antibodies, which bind to foreign substances such as bacteria and target them for destruction. Still other proteins carry messages or materials. For example, human red blood cells contain a protein called hemoglobin, which binds with oxygen. Hemoglobin allows the blood to carry oxygen from the lungs to cells throughout the body. A model of the hemoglobin molecule is shown in Figure below . Q: What type of proteins bind to foreign substances and attempt destruction? Choices: - membranes - ribosomes - antigens - antibodies A:
A:
antibodies