The selective expression of proteins like MSI60 and MSI31 in different layers of these objects likely help control substrate polymorphs. These objects’ resilience is partially due to a large, spring-like protein called lustrin A. These objects’ matrices consist of beta-chitin (“KY-tin”) sandwiched between beta-sheets of glycine and alanine-rich fibroin (“FY-broh-in”)-like proteins, all coated in a layer of aspartic acid-rich proteins. These objects incorporate a material in which hexagonal, close-packed platelets form a regular “brick wall” structure. That biocomposite aragonite found in these objects is responsible for their iridescent structural coloration. These objects consist of a periostracum, a prismatic layer, and a lustrous nacreous layer. They’re not trees, but these objects grow at their distal edges, leading to growth lines and characteristic spiral shapes. For 10 points, name these calcified protective structures formed by mollusks like conchs. ■END■
ANSWER: mollusk shells [accept seashells; accept valves; prompt on nacre until “nacreous” is read; prompt on mother-of-pearl; prompt on pearls; prompt on bivalves; prompt on exoskeletons]
<Biology>
= Average correct buzz position