Final answer:
The newly synthesized MHC II alpha and beta chains are translocated from ribosomes into the endoplasmic reticulum (ER) membrane.
Step-by-step explanation:
The newly synthesized MHC II alpha and beta chains are translocated from ribosomes into the endoplasmic reticulum (ER) membrane.
MHC II molecules are expressed only on the surface of antigen-presenting cells, such as macrophages, dendritic cells, and B cells.
The MHC II molecules are synthesized as a precursor protein within the ribosomes.
As the nascent polypeptide chain is being formed, it is translocated into the ER membrane through a process called co-translational translocation.
This process ensures that the MHC II chains are properly folded and processed into their biologically active form within the ER.