Point 9 of 11 — Lesson 2: The Human Immune System (Organs, Cells, and Antibodies)Question bank: 29 questions (23 with pictures)
10Structure of an antibody
The molecule isY-shapedand made offour polypeptide chains: two long (heavy) chains and two short (light) chains, held together bydisulphide bonds.
Each antibody hastwo identical antigen-binding sites, located at thetips of the two arms of the Y. The fit between antigen and binding site resembles a lock and key, and the union forms an antigen–antibody complex.
The tip regions are the variable regions (V): their shape differs from one antibody to another. The remainder of the molecule is the constant region (C), the same in structure for a given class of antibody. A flexible hinge regionlets the arms swing.
Specificity depends on the amino-acid sequence, type and three-dimensional shape in the variable regionat the binding site.
📝 Question bank for this point
29 questions linked to this point only, 23 of them with pictures.
