The sequence for the processing of proteins originating outside of the cell is...
A) Proteins are broken into fragments, transported to the rough endoplasmic reticulum, fuse with a Golgi vesicle containing class II MHCs, and this complex is transported to the plasma membrane.
B) Proteins are broken into fragments within a vesicle, which fuses with a Golgi vesicle containing class I MHCs, and this complex is transported to the plasma membrane.
C) Proteins are broken into fragments within a vesicle, which fuses with a Golgi vesicle containing class II MHCs, and this complex is transported to the plasma membrane.
D) Proteins are broken into fragments, transported to the rough endoplasmic reticulum, combined with class II MHCs, move to the Golgi apparatus, then to the plasma membrane.
E) Proteins are broken into fragments, transported to the rough endoplasmic reticulum, combined with class I MHCs, move to the Golgi apparatus, then to the plasma membrane.

Question

Quizplus · Accepted Answer

Proteins originating outside of the cell are processed through a pathway involving their breakdown into fragments within a vesicle. This vesicle then fuses with another vesicle containing class II Major Histocompatibility Complex (MHC) molecules. The resulting complex is then transported to the plasma membrane. This process is part of the antigen presentation mechanism by which cells present foreign proteins to the immune system, specifically to helper T cells via class II MHC molecules.

The Sequence for the Processing of Proteins Originating Outside of the Cell