Question

ricin is one of the most powerful toxins known. the protein consists of two subunits: the a chain is an enzyme that inhibits translation and the b chain is a lectin that binds to carbohydrates on the cell surface. what is the most likely mechanism by which ricin enters the cell? choose one: the protein is internalized by endocytosis. the a chain binds to clathrin. the a chain stimulates autophagy. the b chain interacts with snares. the protein enters through pore complexes in the plasma membrane.

Explanation:

Ricin is a large protein. Endocytosis is a common mechanism for large - sized molecules like proteins to enter cells. The B chain of ricin binds to carbohydrates on the cell surface, which can trigger the cell to internalize the ricin - carbohydrate complex through endocytosis. The other options are less likely as there is no evidence to suggest that the A chain binds to clathrin, stimulates autophagy, or that the B chain interacts with SNARES, and large proteins do not typically enter through plasma - membrane pore complexes.

Answer:

The protein is internalized by endocytosis.